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<title>GNU GRUB Manual 2.12</title>

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<p>
Next: <a href="#Introduction" accesskey="n" rel="next">Introduction to GRUB</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
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<h1 class="top" id="GNU-GRUB-manual"><span>GNU GRUB manual<a class="copiable-link" href="#GNU-GRUB-manual"> &para;</a></span></h1>

<p>This is the documentation of GNU GRUB, the GRand Unified Bootloader,
a flexible and powerful boot loader program for a wide range of
architectures.
</p>
<p>This edition documents version 2.12.
</p>
<p>This manual is for GNU GRUB (version 2.12,
20 April 2026).
</p>
<p>Copyright &copy; 1999,2000,2001,2002,2004,2006,2008,2009,2010,2011,2012,2013 Free Software Foundation, Inc.
</p>
<blockquote class="quotation">
<p>Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no
Invariant Sections.
</p></blockquote>

<div class="element-contents" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>

<ul class="toc-numbered-mark">
  <li><a id="toc-Introduction-to-GRUB" href="#Introduction">1 Introduction to GRUB</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Overview-1" href="#Overview">1.1 Overview</a></li>
    <li><a id="toc-History-of-GRUB" href="#History">1.2 History of GRUB</a></li>
    <li><a id="toc-Differences-from-previous-versions" href="#Changes-from-GRUB-Legacy">1.3 Differences from previous versions</a></li>
    <li><a id="toc-GRUB-features" href="#Features">1.4 GRUB features</a></li>
    <li><a id="toc-The-role-of-a-boot-loader" href="#Role-of-a-boot-loader">1.5 The role of a boot loader</a></li>
  </ul></li>
  <li><a id="toc-Naming-convention-1" href="#Naming-convention">2 Naming convention</a></li>
  <li><a id="toc-OS_002dspecific-notes-about-grub-tools-1" href="#OS_002dspecific-notes-about-grub-tools">3 OS-specific notes about grub tools</a></li>
  <li><a id="toc-Installation-1" href="#Installation">4 Installation</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Installing-GRUB-using-grub2_002dinstall-1" href="#Installing-GRUB-using-grub2_002dinstall">4.1 Installing GRUB using grub2-install</a></li>
    <li><a id="toc-Making-a-GRUB-bootable-CD_002dROM-1" href="#Making-a-GRUB-bootable-CD_002dROM">4.2 Making a GRUB bootable CD-ROM</a></li>
    <li><a id="toc-The-map-between-BIOS-drives-and-OS-devices" href="#Device-map">4.3 The map between BIOS drives and OS devices</a></li>
    <li><a id="toc-BIOS-installation-1" href="#BIOS-installation">4.4 BIOS installation</a></li>
  </ul></li>
  <li><a id="toc-Booting-1" href="#Booting">5 Booting</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-How-to-boot-operating-systems" href="#General-boot-methods">5.1 How to boot operating systems</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-How-to-boot-an-OS-directly-with-GRUB" href="#Loading-an-operating-system-directly">5.1.1 How to boot an OS directly with GRUB</a></li>
      <li><a id="toc-Kexec-with-grub2_002demu" href="#Kexec">5.1.2 Kexec with grub2-emu</a></li>
      <li><a id="toc-Chain_002dloading-an-OS" href="#Chain_002dloading">5.1.3 Chain-loading an OS</a></li>
    </ul></li>
    <li><a id="toc-Loopback-booting-1" href="#Loopback-booting">5.2 Loopback booting</a></li>
    <li><a id="toc-Booting-from-LVM-cache-logical-volume" href="#LVM-cache-booting">5.3 Booting from LVM cache logical volume</a></li>
    <li><a id="toc-Some-caveats-on-OS_002dspecific-issues" href="#OS_002dspecific-notes">5.4 Some caveats on OS-specific issues</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-GNU_002fHurd-1" href="#GNU_002fHurd">5.4.1 GNU/Hurd</a></li>
      <li><a id="toc-GNU_002fLinux-1" href="#GNU_002fLinux">5.4.2 GNU/Linux</a></li>
      <li><a id="toc-NetBSD-1" href="#NetBSD">5.4.3 NetBSD</a></li>
      <li><a id="toc-DOS_002fWindows-1" href="#DOS_002fWindows">5.4.4 DOS/Windows</a></li>
    </ul></li>
  </ul></li>
  <li><a id="toc-Writing-your-own-configuration-file" href="#Configuration">6 Writing your own configuration file</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Simple-configuration-handling" href="#Simple-configuration">6.1 Simple configuration handling</a></li>
    <li><a id="toc-Root-Identifcation-Heuristics-1" href="#Root-Identifcation-Heuristics">6.2 Root Identifcation Heuristics</a></li>
    <li><a id="toc-Writing-full-configuration-files-directly" href="#Shell_002dlike-scripting">6.3 Writing full configuration files directly</a></li>
    <li><a id="toc-Multi_002dboot-manual-config-1" href="#Multi_002dboot-manual-config">6.4 Multi-boot manual config</a></li>
    <li><a id="toc-Embedding-a-configuration-file-into-GRUB" href="#Embedded-configuration">6.5 Embedding a configuration file into GRUB</a></li>
  </ul></li>
  <li><a id="toc-Theme-file-format-1" href="#Theme-file-format">7 Theme file format</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Introduction-1" href="#Introduction-1">7.1 Introduction</a></li>
    <li><a id="toc-Theme-Elements" href="#Theme-Elements">7.2 Theme Elements</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-Colors" href="#Colors">7.2.1 Colors</a></li>
      <li><a id="toc-Fonts" href="#Fonts">7.2.2 Fonts</a></li>
      <li><a id="toc-Progress-Bar" href="#Progress-Bar">7.2.3 Progress Bar</a></li>
      <li><a id="toc-Circular-Progress-Indicator" href="#Circular-Progress-Indicator">7.2.4 Circular Progress Indicator</a></li>
      <li><a id="toc-Labels" href="#Labels">7.2.5 Labels</a></li>
      <li><a id="toc-Boot-Menu" href="#Boot-Menu">7.2.6 Boot Menu</a></li>
      <li><a id="toc-Styled-Boxes" href="#Styled-Boxes">7.2.7 Styled Boxes</a></li>
      <li><a id="toc-Creating-Styled-Box-Images" href="#Creating-Styled-Box-Images">7.2.8 Creating Styled Box Images</a></li>
    </ul></li>
    <li><a id="toc-Theme-File-Manual" href="#Theme-File-Manual">7.3 Theme File Manual</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-Global-Properties" href="#Global-Properties">7.3.1 Global Properties</a></li>
      <li><a id="toc-Format" href="#Format">7.3.2 Format</a></li>
      <li><a id="toc-Global-Property-List" href="#Global-Property-List">7.3.3 Global Property List</a></li>
      <li><a id="toc-Component-Construction" href="#Component-Construction">7.3.4 Component Construction</a></li>
      <li><a id="toc-Component-List" href="#Component-List">7.3.5 Component List</a></li>
      <li><a id="toc-Common-properties" href="#Common-properties">7.3.6 Common properties</a></li>
    </ul></li>
  </ul></li>
  <li><a id="toc-Booting-GRUB-from-the-network" href="#Network">8 Booting GRUB from the network</a></li>
  <li><a id="toc-Using-GRUB-via-a-serial-line" href="#Serial-terminal">9 Using GRUB via a serial line</a></li>
  <li><a id="toc-Using-GRUB-with-vendor-power_002don-keys" href="#Vendor-power_002don-keys">10 Using GRUB with vendor power-on keys</a></li>
  <li><a id="toc-GRUB-image-files" href="#Images">11 GRUB image files</a></li>
  <li><a id="toc-Core-image-size-limitation-1" href="#Core-image-size-limitation">12 Core image size limitation</a></li>
  <li><a id="toc-Filesystem-syntax-and-semantics" href="#Filesystem">13 Filesystem syntax and semantics</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-How-to-specify-devices" href="#Device-syntax">13.1 How to specify devices</a></li>
    <li><a id="toc-How-to-specify-files" href="#File-name-syntax">13.2 How to specify files</a></li>
    <li><a id="toc-How-to-specify-block-lists" href="#Block-list-syntax">13.3 How to specify block lists</a></li>
  </ul></li>
  <li><a id="toc-GRUB_0027s-user-interface" href="#Interface">14 GRUB&rsquo;s user interface</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-The-flexible-command_002dline-interface" href="#Command_002dline-interface">14.1 The flexible command-line interface</a></li>
    <li><a id="toc-The-simple-menu-interface" href="#Menu-interface">14.2 The simple menu interface</a></li>
    <li><a id="toc-Editing-a-menu-entry" href="#Menu-entry-editor">14.3 Editing a menu entry</a></li>
  </ul></li>
  <li><a id="toc-GRUB-environment-variables" href="#Environment">15 GRUB environment variables</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Special-environment-variables-1" href="#Special-environment-variables">15.1 Special environment variables</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-appendedsig_005fkey_005fmgmt-1" href="#appendedsig_005fkey_005fmgmt">15.1.1 appendedsig_key_mgmt</a></li>
      <li><a id="toc-biosnum-1" href="#biosnum">15.1.2 biosnum</a></li>
      <li><a id="toc-blsuki_005fsave_005fdefault-1" href="#blsuki_005fsave_005fdefault">15.1.3 blsuki_save_default</a></li>
      <li><a id="toc-check_005fappended_005fsignatures-1" href="#check_005fappended_005fsignatures">15.1.4 check_appended_signatures</a></li>
      <li><a id="toc-check_005fsignatures-1" href="#check_005fsignatures">15.1.5 check_signatures</a></li>
      <li><a id="toc-chosen-1" href="#chosen">15.1.6 chosen</a></li>
      <li><a id="toc-cmdpath-1" href="#cmdpath">15.1.7 cmdpath</a></li>
      <li><a id="toc-color_005fhighlight-1" href="#color_005fhighlight">15.1.8 color_highlight</a></li>
      <li><a id="toc-color_005fnormal-1" href="#color_005fnormal">15.1.9 color_normal</a></li>
      <li><a id="toc-config_005fdirectory-1" href="#config_005fdirectory">15.1.10 config_directory</a></li>
      <li><a id="toc-config_005ffile-1" href="#config_005ffile">15.1.11 config_file</a></li>
      <li><a id="toc-debug-1" href="#debug">15.1.12 debug</a></li>
      <li><a id="toc-default-1" href="#default">15.1.13 default</a></li>
      <li><a id="toc-fallback-1" href="#fallback">15.1.14 fallback</a></li>
      <li><a id="toc-gfxmode-1" href="#gfxmode">15.1.15 gfxmode</a></li>
      <li><a id="toc-gfxpayload-1" href="#gfxpayload">15.1.16 gfxpayload</a></li>
      <li><a id="toc-gfxterm_005ffont-1" href="#gfxterm_005ffont">15.1.17 gfxterm_font</a></li>
      <li><a id="toc-grub_005fcpu-1" href="#grub_005fcpu">15.1.18 grub_cpu</a></li>
      <li><a id="toc-grub_005fplatform-1" href="#grub_005fplatform">15.1.19 grub_platform</a></li>
      <li><a id="toc-icondir-1" href="#icondir">15.1.20 icondir</a></li>
      <li><a id="toc-lang-1" href="#lang">15.1.21 lang</a></li>
      <li><a id="toc-locale_005fdir-1" href="#locale_005fdir">15.1.22 locale_dir</a></li>
      <li><a id="toc-lockdown-1" href="#lockdown">15.1.23 lockdown</a></li>
      <li><a id="toc-menu_005fcolor_005fhighlight-1" href="#menu_005fcolor_005fhighlight">15.1.24 menu_color_highlight</a></li>
      <li><a id="toc-menu_005fcolor_005fnormal-1" href="#menu_005fcolor_005fnormal">15.1.25 menu_color_normal</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fboot_005ffile-1" href="#net_005f_003cinterface_003e_005fboot_005ffile">15.1.26 net_<var class="var">&lt;interface&gt;</var>_boot_file</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fclientid-1" href="#net_005f_003cinterface_003e_005fclientid">15.1.27 net_<var class="var">&lt;interface&gt;</var>_clientid</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fclientuuid-1" href="#net_005f_003cinterface_003e_005fclientuuid">15.1.28 net_<var class="var">&lt;interface&gt;</var>_clientuuid</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fdhcp_005fserver_005fname-1" href="#net_005f_003cinterface_003e_005fdhcp_005fserver_005fname">15.1.29 net_<var class="var">&lt;interface&gt;</var>_dhcp_server_name</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fdomain-1" href="#net_005f_003cinterface_003e_005fdomain">15.1.30 net_<var class="var">&lt;interface&gt;</var>_domain</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fextensionspath-1" href="#net_005f_003cinterface_003e_005fextensionspath">15.1.31 net_<var class="var">&lt;interface&gt;</var>_extensionspath</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fhostname-1" href="#net_005f_003cinterface_003e_005fhostname">15.1.32 net_<var class="var">&lt;interface&gt;</var>_hostname</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fip-1" href="#net_005f_003cinterface_003e_005fip">15.1.33 net_<var class="var">&lt;interface&gt;</var>_ip</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fmac-1" href="#net_005f_003cinterface_003e_005fmac">15.1.34 net_<var class="var">&lt;interface&gt;</var>_mac</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005fnext_005fserver-1" href="#net_005f_003cinterface_003e_005fnext_005fserver">15.1.35 net_<var class="var">&lt;interface&gt;</var>_next_server</a></li>
      <li><a id="toc-net_005f_003cinterface_003e_005frootpath-1" href="#net_005f_003cinterface_003e_005frootpath">15.1.36 net_<var class="var">&lt;interface&gt;</var>_rootpath</a></li>
      <li><a id="toc-net_005fdefault_005finterface-1" href="#net_005fdefault_005finterface">15.1.37 net_default_interface</a></li>
      <li><a id="toc-net_005fdefault_005fip-1" href="#net_005fdefault_005fip">15.1.38 net_default_ip</a></li>
      <li><a id="toc-net_005fdefault_005fmac-1" href="#net_005fdefault_005fmac">15.1.39 net_default_mac</a></li>
      <li><a id="toc-net_005fdefault_005fserver-1" href="#net_005fdefault_005fserver">15.1.40 net_default_server</a></li>
      <li><a id="toc-pager-1" href="#pager">15.1.41 pager</a></li>
      <li><a id="toc-prefix-1" href="#prefix">15.1.42 prefix</a></li>
      <li><a id="toc-pxe_005fblksize-1" href="#pxe_005fblksize">15.1.43 pxe_blksize</a></li>
      <li><a id="toc-pxe_005fdefault_005fgateway-1" href="#pxe_005fdefault_005fgateway">15.1.44 pxe_default_gateway</a></li>
      <li><a id="toc-pxe_005fdefault_005fserver-1" href="#pxe_005fdefault_005fserver">15.1.45 pxe_default_server</a></li>
      <li><a id="toc-root-1" href="#root">15.1.46 root</a></li>
      <li><a id="toc-shim_005flock-1" href="#shim_005flock">15.1.47 shim_lock</a></li>
      <li><a id="toc-superusers-1" href="#superusers">15.1.48 superusers</a></li>
      <li><a id="toc-theme-1" href="#theme">15.1.49 theme</a></li>
      <li><a id="toc-timeout-1" href="#timeout">15.1.50 timeout</a></li>
      <li><a id="toc-timeout_005fstyle-1" href="#timeout_005fstyle">15.1.51 timeout_style</a></li>
      <li><a id="toc-tpm_005ffail_005ffatal-1" href="#tpm_005ffail_005ffatal">15.1.52 tpm_fail_fatal</a></li>
    </ul></li>
    <li><a id="toc-The-GRUB-environment-block" href="#Environment-block">15.2 The GRUB environment block</a></li>
  </ul></li>
  <li><a id="toc-Modules-1" href="#Modules">16 Modules</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-bli-1" href="#bli">16.1 bli</a></li>
  </ul></li>
  <li><a id="toc-Available-commands" href="#Commands">17 Available commands</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Commands-for-the-menu-only" href="#Menu_002dspecific-commands">17.1 Commands for the menu only</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-menuentry-1" href="#menuentry">17.1.1 menuentry</a></li>
      <li><a id="toc-submenu-1" href="#submenu">17.1.2 submenu</a></li>
    </ul></li>
    <li><a id="toc-Various-loader-commands" href="#Loader-commands">17.2 Various loader commands</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-chainloader-1" href="#chainloader">17.2.1 chainloader</a></li>
      <li><a id="toc-initrd-1" href="#initrd">17.2.2 initrd</a></li>
      <li><a id="toc-initrd16-1" href="#initrd16">17.2.3 initrd16</a></li>
      <li><a id="toc-linux-1" href="#linux">17.2.4 linux</a></li>
      <li><a id="toc-linux16-1" href="#linux16">17.2.5 linux16</a></li>
      <li><a id="toc-xen_005fhypervisor-1" href="#xen_005fhypervisor">17.2.6 xen_hypervisor</a></li>
      <li><a id="toc-xen_005fmodule-1" href="#xen_005fmodule">17.2.7 xen_module</a></li>
    </ul></li>
    <li><a id="toc-General-commands-1" href="#General-commands">17.3 General commands</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-serial-1" href="#serial">17.3.1 serial</a></li>
      <li><a id="toc-terminal_005finput-1" href="#terminal_005finput">17.3.2 terminal_input</a></li>
      <li><a id="toc-terminal_005foutput-1" href="#terminal_005foutput">17.3.3 terminal_output</a></li>
      <li><a id="toc-terminfo-1" href="#terminfo">17.3.4 terminfo</a></li>
    </ul></li>
    <li><a id="toc-Command_002dline-commands-1" href="#Command_002dline-commands">17.4 Command-line commands</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-_005b-1" href="#g_t_005b">17.4.1 [</a></li>
      <li><a id="toc-acpi-1" href="#acpi">17.4.2 acpi</a></li>
      <li><a id="toc-append_005fadd_005fdb_005fcert-1" href="#append_005fadd_005fdb_005fcert">17.4.3 append_add_db_cert</a></li>
      <li><a id="toc-append_005fadd_005fdb_005fhash-1" href="#append_005fadd_005fdb_005fhash">17.4.4 append_add_db_hash</a></li>
      <li><a id="toc-append_005fadd_005fdbx_005fcert-1" href="#append_005fadd_005fdbx_005fcert">17.4.5 append_add_dbx_cert</a></li>
      <li><a id="toc-append_005fadd_005fdbx_005fhash-1" href="#append_005fadd_005fdbx_005fhash">17.4.6 append_add_dbx_hash</a></li>
      <li><a id="toc-append_005flist_005fdb-1" href="#append_005flist_005fdb">17.4.7 append_list_db</a></li>
      <li><a id="toc-append_005flist_005fdbx-1" href="#append_005flist_005fdbx">17.4.8 append_list_dbx</a></li>
      <li><a id="toc-append_005fverify-1" href="#append_005fverify">17.4.9 append_verify</a></li>
      <li><a id="toc-authenticate-1" href="#authenticate">17.4.10 authenticate</a></li>
      <li><a id="toc-background_005fcolor-1" href="#background_005fcolor">17.4.11 background_color</a></li>
      <li><a id="toc-background_005fimage-1" href="#background_005fimage">17.4.12 background_image</a></li>
      <li><a id="toc-badram-1" href="#badram">17.4.13 badram</a></li>
      <li><a id="toc-blocklist-1" href="#blocklist">17.4.14 blocklist</a></li>
      <li><a id="toc-blscfg-1" href="#blscfg">17.4.15 blscfg</a></li>
      <li><a id="toc-boot-1" href="#boot">17.4.16 boot</a></li>
      <li><a id="toc-cat-1" href="#cat">17.4.17 cat</a></li>
      <li><a id="toc-clear-1" href="#clear">17.4.18 clear</a></li>
      <li><a id="toc-cmosclean-1" href="#cmosclean">17.4.19 cmosclean</a></li>
      <li><a id="toc-cmosdump-1" href="#cmosdump">17.4.20 cmosdump</a></li>
      <li><a id="toc-cmostest-1" href="#cmostest">17.4.21 cmostest</a></li>
      <li><a id="toc-cmp-1" href="#cmp">17.4.22 cmp</a></li>
      <li><a id="toc-configfile-1" href="#configfile">17.4.23 configfile</a></li>
      <li><a id="toc-cpuid-1" href="#cpuid">17.4.24 cpuid</a></li>
      <li><a id="toc-crc-1" href="#crc">17.4.25 crc</a></li>
      <li><a id="toc-cryptomount-1" href="#cryptomount">17.4.26 cryptomount</a></li>
      <li><a id="toc-cutmem-1" href="#cutmem">17.4.27 cutmem</a></li>
      <li><a id="toc-date-1" href="#date">17.4.28 date</a></li>
      <li><a id="toc-devicetree-1" href="#devicetree">17.4.29 devicetree</a></li>
      <li><a id="toc-distrust-1" href="#distrust">17.4.30 distrust</a></li>
      <li><a id="toc-distrust_005fcertificate-1" href="#distrust_005fcertificate">17.4.31 distrust_certificate</a></li>
      <li><a id="toc-drivemap-1" href="#drivemap">17.4.32 drivemap</a></li>
      <li><a id="toc-echo-1" href="#echo">17.4.33 echo</a></li>
      <li><a id="toc-efitextmode-1" href="#efitextmode">17.4.34 efitextmode</a></li>
      <li><a id="toc-eval-1" href="#eval">17.4.35 eval</a></li>
      <li><a id="toc-export-1" href="#export">17.4.36 export</a></li>
      <li><a id="toc-false-1" href="#false">17.4.37 false</a></li>
      <li><a id="toc-fwsetup-1" href="#fwsetup">17.4.38 fwsetup</a></li>
      <li><a id="toc-gdbinfo-1" href="#gdbinfo">17.4.39 gdbinfo</a></li>
      <li><a id="toc-gettext-1" href="#gettext">17.4.40 gettext</a></li>
      <li><a id="toc-gptsync-1" href="#gptsync">17.4.41 gptsync</a></li>
      <li><a id="toc-halt-1" href="#halt">17.4.42 halt</a></li>
      <li><a id="toc-hashsum-1" href="#hashsum">17.4.43 hashsum</a></li>
      <li><a id="toc-help-1" href="#help">17.4.44 help</a></li>
      <li><a id="toc-hexdump-1" href="#hexdump">17.4.45 hexdump</a></li>
      <li><a id="toc-insmod-1" href="#insmod">17.4.46 insmod</a></li>
      <li><a id="toc-keystatus-1" href="#keystatus">17.4.47 keystatus</a></li>
      <li><a id="toc-list_005fcertificates-1" href="#list_005fcertificates">17.4.48 list_certificates</a></li>
      <li><a id="toc-list_005fenv-1" href="#list_005fenv">17.4.49 list_env</a></li>
      <li><a id="toc-list_005ftrusted-1" href="#list_005ftrusted">17.4.50 list_trusted</a></li>
      <li><a id="toc-load_005fenv-1" href="#load_005fenv">17.4.51 load_env</a></li>
      <li><a id="toc-loadfont-1" href="#loadfont">17.4.52 loadfont</a></li>
      <li><a id="toc-loopback-1" href="#loopback">17.4.53 loopback</a></li>
      <li><a id="toc-ls-1" href="#ls">17.4.54 ls</a></li>
      <li><a id="toc-lsfonts-1" href="#lsfonts">17.4.55 lsfonts</a></li>
      <li><a id="toc-lsmod-1" href="#lsmod">17.4.56 lsmod</a></li>
      <li><a id="toc-md5sum-1" href="#md5sum">17.4.57 md5sum</a></li>
      <li><a id="toc-module-1" href="#module">17.4.58 module</a></li>
      <li><a id="toc-multiboot-1" href="#multiboot">17.4.59 multiboot</a></li>
      <li><a id="toc-nativedisk-1" href="#nativedisk">17.4.60 nativedisk</a></li>
      <li><a id="toc-normal-1" href="#normal">17.4.61 normal</a></li>
      <li><a id="toc-normal_005fexit-1" href="#normal_005fexit">17.4.62 normal_exit</a></li>
      <li><a id="toc-parttool-1" href="#parttool">17.4.63 parttool</a></li>
      <li><a id="toc-password-1" href="#password">17.4.64 password</a></li>
      <li><a id="toc-password_005fpbkdf2-1" href="#password_005fpbkdf2">17.4.65 password_pbkdf2</a></li>
      <li><a id="toc-plainmount-1" href="#plainmount">17.4.66 plainmount</a></li>
      <li><a id="toc-play-1" href="#play">17.4.67 play</a></li>
      <li><a id="toc-probe-1" href="#probe">17.4.68 probe</a></li>
      <li><a id="toc-rdmsr-1" href="#rdmsr">17.4.69 rdmsr</a></li>
      <li><a id="toc-read-1" href="#read">17.4.70 read</a></li>
      <li><a id="toc-reboot-1" href="#reboot">17.4.71 reboot</a></li>
      <li><a id="toc-regexp-1" href="#regexp">17.4.72 regexp</a></li>
      <li><a id="toc-rmmod-1" href="#rmmod">17.4.73 rmmod</a></li>
      <li><a id="toc-save_005fenv-1" href="#save_005fenv">17.4.74 save_env</a></li>
      <li><a id="toc-search-1" href="#search">17.4.75 search</a></li>
      <li><a id="toc-sendkey-1" href="#sendkey">17.4.76 sendkey</a></li>
      <li><a id="toc-set-1" href="#set">17.4.77 set</a></li>
      <li><a id="toc-sha1sum-1" href="#sha1sum">17.4.78 sha1sum</a></li>
      <li><a id="toc-sha256sum-1" href="#sha256sum">17.4.79 sha256sum</a></li>
      <li><a id="toc-sha512sum-1" href="#sha512sum">17.4.80 sha512sum</a></li>
      <li><a id="toc-sleep-1" href="#sleep">17.4.81 sleep</a></li>
      <li><a id="toc-smbios-1" href="#smbios">17.4.82 smbios</a></li>
      <li><a id="toc-source-1" href="#source">17.4.83 source</a></li>
      <li><a id="toc-test-1" href="#test">17.4.84 test</a></li>
      <li><a id="toc-true-1" href="#true">17.4.85 true</a></li>
      <li><a id="toc-trust-1" href="#trust">17.4.86 trust</a></li>
      <li><a id="toc-trust_005fcertificate-1" href="#trust_005fcertificate">17.4.87 trust_certificate</a></li>
      <li><a id="toc-unset-1" href="#unset">17.4.88 unset</a></li>
      <li><a id="toc-uki-1" href="#uki">17.4.89 uki</a></li>
      <li><a id="toc-verify_005fappended-1" href="#verify_005fappended">17.4.90 verify_appended</a></li>
      <li><a id="toc-verify_005fdetached-1" href="#verify_005fdetached">17.4.91 verify_detached</a></li>
      <li><a id="toc-videoinfo-1" href="#videoinfo">17.4.92 videoinfo</a></li>
      <li><a id="toc-wrmsr-1" href="#wrmsr">17.4.93 wrmsr</a></li>
    </ul></li>
    <li><a id="toc-Networking-commands-1" href="#Networking-commands">17.5 Networking commands</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-net_005fadd_005faddr-1" href="#net_005fadd_005faddr">17.5.1 net_add_addr</a></li>
      <li><a id="toc-net_005fadd_005fdns-1" href="#net_005fadd_005fdns">17.5.2 net_add_dns</a></li>
      <li><a id="toc-net_005fadd_005froute-1" href="#net_005fadd_005froute">17.5.3 net_add_route</a></li>
      <li><a id="toc-net_005fbootp-1" href="#net_005fbootp">17.5.4 net_bootp</a></li>
      <li><a id="toc-net_005fdel_005faddr-1" href="#net_005fdel_005faddr">17.5.5 net_del_addr</a></li>
      <li><a id="toc-net_005fdel_005fdns-1" href="#net_005fdel_005fdns">17.5.6 net_del_dns</a></li>
      <li><a id="toc-net_005fdel_005froute-1" href="#net_005fdel_005froute">17.5.7 net_del_route</a></li>
      <li><a id="toc-net_005fdhcp-1" href="#net_005fdhcp">17.5.8 net_dhcp</a></li>
      <li><a id="toc-net_005fbootp6-1" href="#net_005fbootp6">17.5.9 net_bootp6</a></li>
      <li><a id="toc-net_005fget_005fdhcp_005foption-1" href="#net_005fget_005fdhcp_005foption">17.5.10 net_get_dhcp_option</a></li>
      <li><a id="toc-net_005fipv6_005fautoconf-1" href="#net_005fipv6_005fautoconf">17.5.11 net_ipv6_autoconf</a></li>
      <li><a id="toc-net_005fls_005faddr-1" href="#net_005fls_005faddr">17.5.12 net_ls_addr</a></li>
      <li><a id="toc-net_005fls_005fcards-1" href="#net_005fls_005fcards">17.5.13 net_ls_cards</a></li>
      <li><a id="toc-net_005fls_005fdns-1" href="#net_005fls_005fdns">17.5.14 net_ls_dns</a></li>
      <li><a id="toc-net_005fls_005froutes-1" href="#net_005fls_005froutes">17.5.15 net_ls_routes</a></li>
      <li><a id="toc-net_005fnslookup-1" href="#net_005fnslookup">17.5.16 net_nslookup</a></li>
      <li><a id="toc-net_005fset_005fvlan-1" href="#net_005fset_005fvlan">17.5.17 net_set_vlan</a></li>
    </ul></li>
    <li><a id="toc-Commands-currently-undocumented" href="#Undocumented-commands">17.6 Commands currently undocumented</a></li>
  </ul></li>
  <li><a id="toc-Internationalisation-1" href="#Internationalisation">18 Internationalisation</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Charset" href="#Charset">18.1 Charset</a></li>
    <li><a id="toc-Filesystems" href="#Filesystems">18.2 Filesystems</a></li>
    <li><a id="toc-Output-terminal" href="#Output-terminal">18.3 Output terminal</a></li>
    <li><a id="toc-Input-terminal" href="#Input-terminal">18.4 Input terminal</a></li>
    <li><a id="toc-Gettext" href="#Gettext">18.5 Gettext</a></li>
    <li><a id="toc-Regexp" href="#Regexp">18.6 Regexp</a></li>
    <li><a id="toc-Other" href="#Other">18.7 Other</a></li>
  </ul></li>
  <li><a id="toc-Security-1" href="#Security">19 Security</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Authentication-and-authorisation-in-GRUB" href="#Authentication-and-authorisation">19.1 Authentication and authorisation in GRUB</a></li>
    <li><a id="toc-Using-GPG_002dstyle-digital-signatures-in-GRUB" href="#Using-GPG_002dstyle-digital-signatures">19.2 Using GPG-style digital signatures in GRUB</a></li>
    <li><a id="toc-Using-appended-signatures-in-GRUB" href="#Using-appended-signatures">19.3 Using appended signatures in GRUB</a></li>
    <li><a id="toc-UEFI-secure-boot-and-shim-support" href="#UEFI-secure-boot-and-shim">19.4 UEFI secure boot and shim support</a></li>
    <li><a id="toc-Embedded-information-for-generation-number-based-revocation" href="#Secure-Boot-Advanced-Targeting">19.5 Embedded information for generation number based revocation</a></li>
    <li><a id="toc-Measuring-boot-components" href="#Measured-Boot">19.6 Measuring boot components</a></li>
    <li><a id="toc-Lockdown-when-booting-on-a-secure-setup" href="#Lockdown">19.7 Lockdown when booting on a secure setup</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-Command-line-and-menuentry-editor-protection" href="#Command-line-and-menuentry-editor-protection">19.7.1 Command line and menuentry editor protection</a></li>
    </ul></li>
    <li><a id="toc-Signing-certificate-and-hash-files-1" href="#Signing-certificate-and-hash-files">19.8 Signing certificate and hash files</a></li>
    <li><a id="toc-Signing-GRUB-itself-1" href="#Signing-GRUB-itself">19.9 Signing GRUB itself</a></li>
    <li><a id="toc-Signing-GRUB-for-UEFI-secure-boot" href="#Signing-GRUB-for-UEFI-secure-boot">19.10 Signing GRUB for UEFI secure boot</a></li>
    <li><a id="toc-Signing-GRUB-with-an-appended-signature" href="#Signing-GRUB-with-an-appended-signature">19.11 Signing GRUB with an appended signature</a></li>
  </ul></li>
  <li><a id="toc-Platform-limitations-1" href="#Platform-limitations">20 Platform limitations</a></li>
  <li><a id="toc-Outline" href="#Platform_002dspecific-operations">21 Outline</a></li>
  <li><a id="toc-Supported-boot-targets" href="#Supported-kernels">22 Supported boot targets</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Boot-tests" href="#Boot-tests">22.1 Boot tests</a></li>
  </ul></li>
  <li><a id="toc-Error-messages-produced-by-GRUB" href="#Troubleshooting">23 Error messages produced by GRUB</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-GRUB-only-offers-a-rescue-shell-1" href="#GRUB-only-offers-a-rescue-shell">23.1 GRUB only offers a rescue shell</a></li>
    <li><a id="toc-Firmware-stalls-instead-of-booting-GRUB-1" href="#Firmware-stalls-instead-of-booting-GRUB">23.2 Firmware stalls instead of booting GRUB</a></li>
  </ul></li>
  <li><a id="toc-User_002dspace-utilities-1" href="#User_002dspace-utilities">24 User-space utilities</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-Invoking-grub2_002dinstall-1" href="#Invoking-grub2_002dinstall">24.1 Invoking grub2-install</a></li>
    <li><a id="toc-Invoking-grub2_002dmkconfig-1" href="#Invoking-grub2_002dmkconfig">24.2 Invoking grub2-mkconfig</a></li>
    <li><a id="toc-Invoking-grub2_002dmkpasswd_002dpbkdf2-1" href="#Invoking-grub2_002dmkpasswd_002dpbkdf2">24.3 Invoking grub2-mkpasswd-pbkdf2</a></li>
    <li><a id="toc-Invoking-grub2_002dmkrelpath-1" href="#Invoking-grub2_002dmkrelpath">24.4 Invoking grub2-mkrelpath</a></li>
    <li><a id="toc-Invoking-grub2_002dmkrescue-1" href="#Invoking-grub2_002dmkrescue">24.5 Invoking grub2-mkrescue</a></li>
    <li><a id="toc-Invoking-grub2_002dmount-1" href="#Invoking-grub2_002dmount">24.6 Invoking grub2-mount</a></li>
    <li><a id="toc-Invoking-grub2_002dprobe-1" href="#Invoking-grub2_002dprobe">24.7 Invoking grub2-probe</a></li>
    <li><a id="toc-Invoking-grub2_002dscript_002dcheck-1" href="#Invoking-grub2_002dscript_002dcheck">24.8 Invoking grub2-script-check</a></li>
  </ul></li>
  <li><a id="toc-How-to-obtain-and-build-GRUB" href="#Obtaining-and-Building-GRUB">Appendix A How to obtain and build GRUB</a></li>
  <li><a id="toc-Reporting-bugs-1" href="#Reporting-bugs">Appendix B Reporting bugs</a></li>
  <li><a id="toc-Where-GRUB-will-go" href="#Future">Appendix C Where GRUB will go</a></li>
  <li><a id="toc-Copying-This-Manual-1" href="#Copying-This-Manual">Appendix D Copying This Manual</a>
  <ul class="toc-numbered-mark">
    <li><a id="toc-GNU-Free-Documentation-License-1" href="#GNU-Free-Documentation-License">D.1 GNU Free Documentation License</a>
    <ul class="toc-numbered-mark">
      <li><a id="toc-ADDENDUM_003a-How-to-use-this-License-for-your-documents" href="#ADDENDUM_003a-How-to-use-this-License-for-your-documents">D.1.1 ADDENDUM: How to use this License for your documents</a></li>
    </ul></li>
  </ul></li>
  <li><a id="toc-Index-1" href="#Index" rel="index">Index</a></li>
</ul>
</div>
</div>
<hr>
<div class="chapter-level-extent" id="Introduction">
<div class="nav-panel">
<p>
Next: <a href="#Naming-convention" accesskey="n" rel="next">Naming convention</a>, Previous: <a href="#Top" accesskey="p" rel="prev">GNU GRUB manual</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Introduction-to-GRUB"><span>1 Introduction to GRUB<a class="copiable-link" href="#Introduction-to-GRUB"> &para;</a></span></h2>

<ul class="mini-toc">
<li><a href="#Overview" accesskey="1">Overview</a></li>
<li><a href="#History" accesskey="2">History of GRUB</a></li>
<li><a href="#Changes-from-GRUB-Legacy" accesskey="3">Differences from previous versions</a></li>
<li><a href="#Features" accesskey="4">GRUB features</a></li>
<li><a href="#Role-of-a-boot-loader" accesskey="5">The role of a boot loader</a></li>
</ul>
<hr>
<div class="section-level-extent" id="Overview">
<div class="nav-panel">
<p>
Next: <a href="#History" accesskey="n" rel="next">History of GRUB</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction to GRUB</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Overview-1"><span>1.1 Overview<a class="copiable-link" href="#Overview-1"> &para;</a></span></h3>

<p>Briefly, a <em class="dfn">boot loader</em> is the first software program that runs when
a computer starts.  It is responsible for loading and transferring
control to an operating system <em class="dfn">kernel</em> software (such as Linux or
GNU Mach).  The kernel, in turn, initializes the rest of the operating
system (e.g. a GNU system).
</p>
<p>GNU GRUB is a very powerful boot loader, which can load a wide variety
of free operating systems, as well as proprietary operating systems with
chain-loading<a class="footnote" id="DOCF1" href="#FOOT1"><sup>1</sup></a>. GRUB is designed to
address the complexity of booting a personal computer; both the
program and this manual are tightly bound to that computer platform,
although porting to other platforms may be addressed in the future.
</p>
<p>One of the important features in GRUB is flexibility; GRUB understands
filesystems and kernel executable formats, so you can load an arbitrary
operating system the way you like, without recording the physical
position of your kernel on the disk. Thus you can load the kernel
just by specifying its file name and the drive and partition where the
kernel resides.
</p>
<p>When booting with GRUB, you can use either a command-line interface
(see <a class="pxref" href="#Command_002dline-interface">The flexible command-line interface</a>), or a menu interface (see <a class="pxref" href="#Menu-interface">The simple menu interface</a>). Using the command-line interface, you type the drive
specification and file name of the kernel manually. In the menu
interface, you just select an OS using the arrow keys. The menu is
based on a configuration file which you prepare beforehand
(see <a class="pxref" href="#Configuration">Writing your own configuration file</a>). While in the menu, you can switch to the
command-line mode, and vice-versa. You can even edit menu entries
before using them.
</p>
<p>In the following chapters, you will learn how to specify a drive, a
partition, and a file name (see <a class="pxref" href="#Naming-convention">Naming convention</a>) to GRUB, how to
install GRUB on your drive (see <a class="pxref" href="#Installation">Installation</a>), and how to boot your
OSes (see <a class="pxref" href="#Booting">Booting</a>), step by step.
</p>

<hr>
</div>
<div class="section-level-extent" id="History">
<div class="nav-panel">
<p>
Next: <a href="#Changes-from-GRUB-Legacy" accesskey="n" rel="next">Differences from previous versions</a>, Previous: <a href="#Overview" accesskey="p" rel="prev">Overview</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction to GRUB</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="History-of-GRUB"><span>1.2 History of GRUB<a class="copiable-link" href="#History-of-GRUB"> &para;</a></span></h3>

<p>GRUB originated in 1995 when Erich Boleyn was trying to boot the GNU
Hurd with the University of Utah&rsquo;s Mach 4 microkernel (now known as GNU
Mach).  Erich and Brian Ford designed the Multiboot Specification
(see <a data-manual="multiboot" href="https://www.gnu.org/software/grub/manual//multiboot/multiboot.html#Top">Motivation</a> in <cite class="cite">The Multiboot
Specification</cite>), because they were determined not to add to the large
number of mutually-incompatible PC boot methods.
</p>
<p>Erich then began modifying the FreeBSD boot loader so that it would
understand Multiboot. He soon realized that it would be a lot easier
to write his own boot loader from scratch than to keep working on the
FreeBSD boot loader, and so GRUB was born.
</p>
<p>Erich added many features to GRUB, but other priorities prevented him
from keeping up with the demands of its quickly-expanding user base. In
1999, Gordon Matzigkeit and Yoshinori K. Okuji adopted GRUB as an
official GNU package, and opened its development by making the latest
sources available via anonymous CVS. See <a class="xref" href="#Obtaining-and-Building-GRUB">How to obtain and build GRUB</a>, for more information.
</p>
<p>Over the next few years, GRUB was extended to meet many needs, but it
quickly became clear that its design was not keeping up with the extensions
being made to it, and we reached the point where it was very difficult to
make any further changes without breaking existing features.  Around 2002,
Yoshinori K. Okuji started work on PUPA (Preliminary Universal Programming
Architecture for GNU GRUB), aiming to rewrite the core of GRUB to make it
cleaner, safer, more robust, and more powerful.  PUPA was eventually renamed
to GRUB 2, and the original version of GRUB was renamed to GRUB Legacy.
Small amounts of maintenance continued to be done on GRUB Legacy, but the
last release (0.97) was made in 2005 and at the time of writing it seems
unlikely that there will be another.
</p>
<p>By around 2007, GNU/Linux distributions started to use GRUB 2 to limited
extents, and by the end of 2009 multiple major distributions were installing
it by default.
</p>

<hr>
</div>
<div class="section-level-extent" id="Changes-from-GRUB-Legacy">
<div class="nav-panel">
<p>
Next: <a href="#Features" accesskey="n" rel="next">GRUB features</a>, Previous: <a href="#History" accesskey="p" rel="prev">History of GRUB</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction to GRUB</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Differences-from-previous-versions"><span>1.3 Differences from previous versions<a class="copiable-link" href="#Differences-from-previous-versions"> &para;</a></span></h3>

<p>GRUB 2 is a rewrite of GRUB (see <a class="pxref" href="#History">History of GRUB</a>), although it shares many
characteristics with the previous version, now known as GRUB Legacy.  Users
of GRUB Legacy may need some guidance to find their way around this new
version.
</p>
<ul class="itemize mark-bullet">
<li>The configuration file has a new name (<samp class="file">grub.cfg</samp> rather than
<samp class="file">menu.lst</samp> or <samp class="file">grub.conf</samp>), new syntax (see <a class="pxref" href="#Configuration">Writing your own configuration file</a>) and
many new commands (see <a class="pxref" href="#Commands">Available commands</a>).  Configuration cannot be copied over
directly, although most GRUB Legacy users should not find the syntax too
surprising.

</li><li><samp class="file">grub.cfg</samp> is typically automatically generated by
<code class="command">grub2-mkconfig</code> (see <a class="pxref" href="#Simple-configuration">Simple configuration handling</a>).  This makes it
easier to handle versioned kernel upgrades.

</li><li>Partition numbers in GRUB device names now start at 1, not 0 (see <a class="pxref" href="#Naming-convention">Naming convention</a>).

</li><li>The configuration file is now written in something closer to a full
scripting language: variables, conditionals, and loops are available.

</li><li>A small amount of persistent storage is available across reboots, using the
<code class="command">save_env</code> and <code class="command">load_env</code> commands in GRUB and the
<code class="command">grub2-editenv</code> utility.  This is not available in all configurations
(see <a class="pxref" href="#Environment-block">The GRUB environment block</a>).

</li><li>GRUB 2 has more reliable ways to find its own files and those of target
kernels on multiple-disk systems, and has commands (see <a class="pxref" href="#search">search</a>) to find
devices using file system labels or Universally Unique Identifiers (UUIDs).

</li><li>GRUB 2 is available for several other types of system in addition to the PC
BIOS systems supported by GRUB Legacy: PC EFI, PC coreboot, PowerPC, SPARC,
and MIPS Lemote Yeeloong are all supported.

</li><li>Many more file systems are supported, including but not limited to ext4,
HFS+, and NTFS.

</li><li>GRUB 2 can read files directly from LVM and RAID devices.

</li><li>A graphical terminal and a graphical menu system are available.

</li><li>GRUB 2&rsquo;s interface can be translated, including menu entry names.

</li><li>The image files (see <a class="pxref" href="#Images">GRUB image files</a>) that make up GRUB have been reorganised;
Stage 1, Stage 1.5, and Stage 2 are no more.

</li><li>GRUB 2 puts many facilities in dynamically loaded modules, allowing the core
image to be smaller, and allowing the core image to be built in more
flexible ways.
</li></ul>

<hr>
</div>
<div class="section-level-extent" id="Features">
<div class="nav-panel">
<p>
Next: <a href="#Role-of-a-boot-loader" accesskey="n" rel="next">The role of a boot loader</a>, Previous: <a href="#Changes-from-GRUB-Legacy" accesskey="p" rel="prev">Differences from previous versions</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction to GRUB</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="GRUB-features"><span>1.4 GRUB features<a class="copiable-link" href="#GRUB-features"> &para;</a></span></h3>

<p>The primary requirement for GRUB is that it be compliant with the
<em class="dfn">Multiboot Specification</em>, which is described in <a data-manual="multiboot" href="https://www.gnu.org/software/grub/manual//multiboot/multiboot.html#Top">Motivation</a> in <cite class="cite">The Multiboot Specification</cite>.
</p>
<p>The other goals, listed in approximate order of importance, are:
</p>
<ul class="itemize mark-bullet">
<li>Basic functions must be straightforward for end-users.

</li><li>Rich functionality to support kernel experts and designers.

</li><li>Backward compatibility for booting FreeBSD, NetBSD, OpenBSD, and
Linux. Proprietary kernels (such as DOS, Windows NT, and OS/2) are
supported via a chain-loading function.
</li></ul>

<p>Except for specific compatibility modes (chain-loading and the Linux
<em class="dfn">piggyback</em> format), all kernels will be started in much the same
state as in the Multiboot Specification. Only kernels loaded at 1 megabyte
or above are presently supported. Any attempt to load below that
boundary will simply result in immediate failure and an error message
reporting the problem.
</p>
<p>In addition to the requirements above, GRUB has the following features
(note that the Multiboot Specification doesn&rsquo;t require all the features
that GRUB supports):
</p>
<dl class="table">
<dt>Recognize multiple executable formats</dt>
<dd><p>Support many of the <em class="dfn">a.out</em> variants plus <em class="dfn">ELF</em>. Symbol
tables are also loaded.
</p>
</dd>
<dt>Support non-Multiboot kernels</dt>
<dd><p>Support many of the various free 32-bit kernels that lack Multiboot
compliance (primarily FreeBSD, NetBSD<a class="footnote" id="DOCF2" href="#FOOT2"><sup>2</sup></a>,
OpenBSD, and Linux). Chain-loading of other boot loaders is also
supported.
</p>
</dd>
<dt>Load multiples modules</dt>
<dd><p>Fully support the Multiboot feature of loading multiple modules.
</p>
</dd>
<dt>Load a configuration file</dt>
<dd><p>Support a human-readable text configuration file with preset boot
commands. You can also load another configuration file dynamically and
embed a preset configuration file in a GRUB image file. The list of
commands (see <a class="pxref" href="#Commands">Available commands</a>) are a superset of those supported on the
command-line. An example configuration file is provided in
<a class="ref" href="#Configuration">Writing your own configuration file</a>.
</p>
</dd>
<dt>Provide a menu interface</dt>
<dd><p>A menu interface listing preset boot commands, with a programmable
timeout, is available. There is no fixed limit on the number of boot
entries, and the current implementation has space for several hundred.
</p>
</dd>
<dt>Have a flexible command-line interface</dt>
<dd><p>A fairly flexible command-line interface, accessible from the menu,
is available to edit any preset commands, or write a new boot command
set from scratch. If no configuration file is present, GRUB drops to
the command-line.
</p>
<p>The list of commands (see <a class="pxref" href="#Commands">Available commands</a>) are a subset of those supported
for configuration files. Editing commands closely resembles the Bash
command-line (see <a data-manual="features" href="features.html#Command-Line-Editing">Command Line Editing</a> in <cite class="cite">Bash Features</cite>), with <kbd class="key">TAB</kbd>-completion of commands,
devices, partitions, and files in a directory depending on context.
</p>
</dd>
<dt>Support multiple filesystem types</dt>
<dd><p>Support multiple filesystem types transparently, plus a useful explicit
blocklist notation. The currently supported filesystem types are <em class="dfn">Amiga
Fast FileSystem (AFFS)</em>, <em class="dfn">AtheOS fs</em>, <em class="dfn">BeFS</em>,
<em class="dfn">BtrFS</em> (including raid0, raid1, raid10, gzip and lzo),
<em class="dfn">cpio</em> (little- and big-endian bin, odc and newc variants),
<em class="dfn">Linux ext2/ext3/ext4</em>, <em class="dfn">DOS FAT12/FAT16/FAT32</em>,
<em class="dfn">exFAT</em>, <em class="dfn">F2FS</em>, <em class="dfn">HFS</em>, <em class="dfn">HFS+</em>,
<em class="dfn">ISO9660</em> (including Joliet, Rock-ridge and multi-chunk files),
<em class="dfn">JFS</em>, <em class="dfn">Minix fs</em> (versions 1, 2 and 3), <em class="dfn">nilfs2</em>,
<em class="dfn">NTFS</em> (including compression), <em class="dfn">ReiserFS</em>, <em class="dfn">ROMFS</em>,
<em class="dfn">Amiga Smart FileSystem (SFS)</em>, <em class="dfn">Squash4</em>, <em class="dfn">tar</em>, <em class="dfn">UDF</em>,
<em class="dfn">BSD UFS/UFS2</em>, <em class="dfn">XFS</em>, and <em class="dfn">ZFS</em> (including lzjb, gzip,
zle, mirror, stripe, raidz1/2/3 and encryption in AES-CCM and AES-GCM).
See <a class="xref" href="#Filesystem">Filesystem syntax and semantics</a>, for more information.
</p>
</dd>
<dt>Support automatic decompression</dt>
<dd><p>Can decompress files which were compressed by <code class="command">gzip</code> or
<code class="command">xz</code><a class="footnote" id="DOCF3" href="#FOOT3"><sup>3</sup></a>. This function is both automatic and transparent to the user
(i.e. all functions operate upon the uncompressed contents of the specified
files). This greatly reduces a file size and loading time, a
particularly great benefit for floppies.<a class="footnote" id="DOCF4" href="#FOOT4"><sup>4</sup></a>
</p>
<p>It is conceivable that some kernel modules should be loaded in a
compressed state, so a different module-loading command can be specified
to avoid uncompressing the modules.
</p>
</dd>
<dt>Access data on any installed device</dt>
<dd><p>Support reading data from any or all floppies or hard disk(s) recognized
by the BIOS, independent of the setting of the root device.
</p>
</dd>
<dt>Be independent of drive geometry translations</dt>
<dd><p>Unlike many other boot loaders, GRUB makes the particular drive
translation irrelevant. A drive installed and running with one
translation may be converted to another translation without any adverse
effects or changes in GRUB&rsquo;s configuration.
</p>
</dd>
<dt>Detect all installed <small class="sc">RAM</small></dt>
<dd><p>GRUB can generally find all the installed <small class="sc">RAM</small> on a PC-compatible
machine. It uses an advanced BIOS query technique for finding all
memory regions. As described on the Multiboot Specification (see <a data-manual="multiboot" href="https://www.gnu.org/software/grub/manual//multiboot/multiboot.html#Top">Motivation</a> in <cite class="cite">The Multiboot
Specification</cite>), not all kernels make use of this information, but GRUB
provides it for those who do.
</p>
</dd>
<dt>Support Logical Block Address mode</dt>
<dd><p>In traditional disk calls (called <em class="dfn">CHS mode</em>), there is a geometry
translation problem, that is, the BIOS cannot access over 1024
cylinders, so the accessible space is limited to at least 508 MB and to
at most 8GB. GRUB can&rsquo;t universally solve this problem, as there is no
standard interface used in all machines. However, several newer machines
have the new interface, Logical Block Address (<em class="dfn">LBA</em>) mode. GRUB
automatically detects if LBA mode is available and uses it if
available. In LBA mode, GRUB can access the entire disk.
</p>
</dd>
<dt>Support network booting</dt>
<dd><p>GRUB is basically a disk-based boot loader but also has network
support. You can load OS images from a network by using the <em class="dfn">TFTP</em>
protocol.
</p>
</dd>
<dt>Support remote terminals</dt>
<dd><p>To support computers with no console, GRUB provides remote terminal
support, so that you can control GRUB from a remote host. Only serial
terminal support is implemented at the moment.
</p></dd>
</dl>

<hr>
</div>
<div class="section-level-extent" id="Role-of-a-boot-loader">
<div class="nav-panel">
<p>
Previous: <a href="#Features" accesskey="p" rel="prev">GRUB features</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction to GRUB</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="The-role-of-a-boot-loader"><span>1.5 The role of a boot loader<a class="copiable-link" href="#The-role-of-a-boot-loader"> &para;</a></span></h3>

<p>The following is a quotation from Gordon Matzigkeit, a GRUB fanatic:
</p>
<blockquote class="quotation">
<p>Some people like to acknowledge both the operating system and kernel when
they talk about their computers, so they might say they use
&ldquo;GNU/Linux&rdquo; or &ldquo;GNU/Hurd&rdquo;.  Other people seem to think that the
kernel is the most important part of the system, so they like to call
their GNU operating systems &ldquo;Linux systems.&rdquo;
</p>
<p>I, personally, believe that this is a grave injustice, because the
<em class="emph">boot loader</em> is the most important software of all. I used to
refer to the above systems as either &ldquo;LILO&rdquo;<a class="footnote" id="DOCF5" href="#FOOT5"><sup>5</sup></a> or &ldquo;GRUB&rdquo;
systems.
</p>
<p>Unfortunately, nobody ever understood what I was talking about; now I
just use the word &ldquo;GNU&rdquo; as a pseudonym for GRUB.
</p>
<p>So, if you ever hear people talking about their alleged &ldquo;GNU&rdquo; systems,
remember that they are actually paying homage to the best boot loader
around&hellip; GRUB!
</p></blockquote>

<p>We, the GRUB maintainers, do not (usually) encourage Gordon&rsquo;s level of
fanaticism, but it helps to remember that boot loaders deserve
recognition.  We hope that you enjoy using GNU GRUB as much as we did
writing it.
</p>

<hr>
</div>
</div>
<div class="chapter-level-extent" id="Naming-convention">
<div class="nav-panel">
<p>
Next: <a href="#OS_002dspecific-notes-about-grub-tools" accesskey="n" rel="next">OS-specific notes about grub tools</a>, Previous: <a href="#Introduction" accesskey="p" rel="prev">Introduction to GRUB</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Naming-convention-1"><span>2 Naming convention<a class="copiable-link" href="#Naming-convention-1"> &para;</a></span></h2>

<p>The device syntax used in GRUB is a wee bit different from what you may
have seen before in your operating system(s), and you need to know it so
that you can specify a drive/partition.
</p>
<p>Look at the following examples and explanations:
</p>
<div class="example">
<pre class="example-preformatted">(fd0)
</pre></div>

<p>First of all, GRUB requires that the device name be enclosed with
&lsquo;<samp class="samp">(</samp>&rsquo; and &lsquo;<samp class="samp">)</samp>&rsquo;. The &lsquo;<samp class="samp">fd</samp>&rsquo; part means that it is a floppy
disk. The number &lsquo;<samp class="samp">0</samp>&rsquo; is the drive number, which is counted from
<em class="emph">zero</em>. This expression means that GRUB will use the whole floppy
disk.
</p>
<div class="example">
<pre class="example-preformatted">(hd0,msdos2)
</pre></div>

<p>Here, &lsquo;<samp class="samp">hd</samp>&rsquo; means it is a hard disk drive. The first integer
&lsquo;<samp class="samp">0</samp>&rsquo; indicates the drive number, that is, the first hard disk,
the string &lsquo;<samp class="samp">msdos</samp>&rsquo; indicates the partition scheme, while
the second integer, &lsquo;<samp class="samp">2</samp>&rsquo;, indicates the partition number (or the
<small class="sc">PC</small> slice number in the BSD terminology). The partition numbers are
counted from <em class="emph">one</em>, not from zero (as was the case in previous
versions of GRUB). This expression means the second partition of the
first hard disk drive. In this case, GRUB uses one partition of the
disk, instead of the whole disk.
</p>
<div class="example">
<pre class="example-preformatted">(hd0,msdos5)
</pre></div>

<p>This specifies the first <em class="dfn">extended partition</em> of the first hard disk
drive. Note that the partition numbers for extended partitions are
counted from &lsquo;<samp class="samp">5</samp>&rsquo;, regardless of the actual number of primary
partitions on your hard disk.
</p>
<div class="example">
<pre class="example-preformatted">(hd1,msdos1,bsd1)
</pre></div>

<p>This means the BSD &lsquo;<samp class="samp">a</samp>&rsquo; partition on first <small class="sc">PC</small> slice number
of the second hard disk.
</p>
<p>Of course, to actually access the disks or partitions with GRUB, you
need to use the device specification in a command, like &lsquo;<samp class="samp">set
root=(fd0)</samp>&rsquo; or &lsquo;<samp class="samp">parttool (hd0,msdos3) hidden-</samp>&rsquo;. To help you find out
which number specifies a partition you want, the GRUB command-line
(see <a class="pxref" href="#Command_002dline-interface">The flexible command-line interface</a>) options have argument
completion. This means that, for example, you only need to type
</p>
<div class="example">
<pre class="example-preformatted">set root=(
</pre></div>

<p>followed by a <kbd class="key">TAB</kbd>, and GRUB will display the list of drives,
partitions, or file names. So it should be quite easy to determine the
name of your target partition, even with minimal knowledge of the
syntax.
</p>
<p>Note that GRUB does <em class="emph">not</em> distinguish IDE from SCSI - it simply
counts the drive numbers from zero, regardless of their type. Normally,
any IDE drive number is less than any SCSI drive number, although that
is not true if you change the boot sequence by swapping IDE and SCSI
drives in your BIOS.
</p>
<p>Now the question is, how to specify a file? Again, consider an
example:
</p>
<div class="example">
<pre class="example-preformatted">(hd0,msdos1)/vmlinuz
</pre></div>

<p>This specifies the file named &lsquo;<samp class="samp">vmlinuz</samp>&rsquo;, found on the first
partition of the first hard disk drive. Note that the argument
completion works with file names, too.
</p>
<p>That was easy, admit it. Now read the next chapter, to find out how to
actually install GRUB on your drive.
</p>
<hr>
</div>
<div class="chapter-level-extent" id="OS_002dspecific-notes-about-grub-tools">
<div class="nav-panel">
<p>
Next: <a href="#Installation" accesskey="n" rel="next">Installation</a>, Previous: <a href="#Naming-convention" accesskey="p" rel="prev">Naming convention</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="OS_002dspecific-notes-about-grub-tools-1"><span>3 OS-specific notes about grub tools<a class="copiable-link" href="#OS_002dspecific-notes-about-grub-tools-1"> &para;</a></span></h2>

<p>On OS which have device nodes similar to Unix-like OS GRUB tools use the
OS name. E.g. for GNU/Linux:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install /dev/sda</kbd>
</pre></div>

<p>On AROS we use another syntax. For volumes:
</p>
<div class="example">
<pre class="example-preformatted">//:&lt;volume name&gt;
</pre></div>

<p>For disks we use syntax:
</p><div class="example">
<pre class="example-preformatted">//:&lt;driver name&gt;/unit/flags
</pre></div>

<p>E.g.
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install //:ata.device/0/0</kbd>
</pre></div>

<p>On Windows we use UNC path. For volumes it&rsquo;s typically
</p>
<div class="example">
<pre class="example-preformatted">\\?\Volume{&lt;GUID&gt;}
\\?\&lt;drive letter&gt;:
</pre></div>

<p>E.g.
</p>
<div class="example">
<pre class="example-preformatted">\\?\Volume{17f34d50-cf64-4b02-800e-51d79c3aa2ff}
\\?\C:
</pre></div>

<p>For disks it&rsquo;s
</p>
<div class="example">
<pre class="example-preformatted">\\?\PhysicalDrive&lt;number&gt;
</pre></div>

<p>E.g.
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install \\?\PhysicalDrive0</kbd>
</pre></div>

<p>Beware that you may need to further escape the backslashes depending on your
shell.
</p>
<p>When compiled with cygwin support then cygwin drive names are automatically
when needed. E.g.
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install /dev/sda</kbd>
</pre></div>

<hr>
</div>
<div class="chapter-level-extent" id="Installation">
<div class="nav-panel">
<p>
Next: <a href="#Booting" accesskey="n" rel="next">Booting</a>, Previous: <a href="#OS_002dspecific-notes-about-grub-tools" accesskey="p" rel="prev">OS-specific notes about grub tools</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Installation-1"><span>4 Installation<a class="copiable-link" href="#Installation-1"> &para;</a></span></h2>

<p>In order to install GRUB as your boot loader, you need to first
install the GRUB system and utilities under your UNIX-like operating
system (see <a class="pxref" href="#Obtaining-and-Building-GRUB">How to obtain and build GRUB</a>). You can do this either
from the source tarball, or as a package for your OS.
</p>
<p>After you have done that, you need to install the boot loader on a
drive (floppy or hard disk) by using the utility
<code class="command">grub2-install</code> (see <a class="pxref" href="#Invoking-grub2_002dinstall">Invoking grub2-install</a>) on a UNIX-like OS.
</p>
<p>GRUB comes with boot images, which are normally put in the directory
<samp class="file">/usr/lib/grub/&lt;cpu&gt;-&lt;platform&gt;</samp> (for BIOS-based machines
<samp class="file">/usr/lib/grub/i386-pc</samp>). Hereafter, the directory where GRUB images are
initially placed (normally <samp class="file">/usr/lib/grub/&lt;cpu&gt;-&lt;platform&gt;</samp>) will be
called the <em class="dfn">image directory</em>, and the directory where the boot
loader needs to find them (usually <samp class="file">/boot</samp>) will be called
the <em class="dfn">boot directory</em>.
</p>

<ul class="mini-toc">
<li><a href="#Installing-GRUB-using-grub2_002dinstall" accesskey="1">Installing GRUB using grub2-install</a></li>
<li><a href="#Making-a-GRUB-bootable-CD_002dROM" accesskey="2">Making a GRUB bootable CD-ROM</a></li>
<li><a href="#Device-map" accesskey="3">The map between BIOS drives and OS devices</a></li>
<li><a href="#BIOS-installation" accesskey="4">BIOS installation</a></li>
</ul>
<hr>
<div class="section-level-extent" id="Installing-GRUB-using-grub2_002dinstall">
<div class="nav-panel">
<p>
Next: <a href="#Making-a-GRUB-bootable-CD_002dROM" accesskey="n" rel="next">Making a GRUB bootable CD-ROM</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Installing-GRUB-using-grub2_002dinstall-1"><span>4.1 Installing GRUB using grub2-install<a class="copiable-link" href="#Installing-GRUB-using-grub2_002dinstall-1"> &para;</a></span></h3>

<p>For information on where GRUB should be installed on PC BIOS platforms,
see <a class="pxref" href="#BIOS-installation">BIOS installation</a>.
</p>
<p>In order to install GRUB under a UNIX-like OS (such
as <small class="sc">GNU</small>), invoke the program <code class="command">grub2-install</code> (see <a class="pxref" href="#Invoking-grub2_002dinstall">Invoking grub2-install</a>) as the superuser (<em class="dfn">root</em>).
</p>
<p>The usage is basically very simple. You only need to specify one
argument to the program, namely, where to install the boot loader. The
argument has to be either a device file (like &lsquo;<samp class="samp">/dev/hda</samp>&rsquo;).
For example, under Linux the following will install GRUB into the MBR
of the first IDE disk:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install /dev/sda</kbd>
</pre></div>

<p>Likewise, under GNU/Hurd, this has the same effect:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install /dev/hd0</kbd>
</pre></div>

<p>But all the above examples assume that GRUB should put images under
the <samp class="file">/boot</samp> directory. If you want GRUB to put images under a directory
other than <samp class="file">/boot</samp>, you need to specify the option
<samp class="option">--boot-directory</samp>. The typical usage is that you create a GRUB
boot floppy with a filesystem. Here is an example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted"># <kbd class="kbd">mke2fs /dev/fd0</kbd>
# <kbd class="kbd">mount -t ext2 /dev/fd0 /mnt</kbd>
# <kbd class="kbd">mkdir /mnt/boot</kbd>
# <kbd class="kbd">grub2-install --boot-directory=/mnt/boot /dev/fd0</kbd>
# <kbd class="kbd">umount /mnt</kbd>
</pre></div></div>

<p>Some BIOSes have a bug of exposing the first partition of a USB drive as a
floppy instead of exposing the USB drive as a hard disk (they call it
&ldquo;USB-FDD&rdquo; boot). In such cases, you need to install like this:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">losetup /dev/loop0 /dev/sdb1</kbd>
# <kbd class="kbd">mount /dev/loop0 /mnt/usb</kbd>
# <kbd class="kbd">grub2-install --boot-directory=/mnt/usb/bugbios --force --allow-floppy /dev/loop0</kbd>
</pre></div>

<p>This install doesn&rsquo;t conflict with standard install as long as they are in
separate directories.
</p>
<p>Note that <code class="command">grub2-install</code> is actually just a shell script and the
real task is done by other tools such as <code class="command">grub2-mkimage</code>. Therefore,
you may run those commands directly to install GRUB, without using
<code class="command">grub2-install</code>. Don&rsquo;t do that, however, unless you are very familiar
with the internals of GRUB. Installing a boot loader on a running OS may be
extremely dangerous.
</p>
<p>On EFI systems for fixed disk install you have to mount EFI System Partition.
If you mount it at <samp class="file">/boot/efi</samp> then you don&rsquo;t need any special arguments:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install</kbd>
</pre></div>

<p>Otherwise you need to specify where your EFI System partition is mounted:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install --efi-directory=/mnt/efi</kbd>
</pre></div>

<p>For removable installs you have to use <samp class="option">--removable</samp> and specify both
<samp class="option">--boot-directory</samp> and <samp class="option">--efi-directory</samp>:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">grub2-install --efi-directory=/mnt/usb --boot-directory=/mnt/usb/boot --removable</kbd>
</pre></div>

<hr>
</div>
<div class="section-level-extent" id="Making-a-GRUB-bootable-CD_002dROM">
<div class="nav-panel">
<p>
Next: <a href="#Device-map" accesskey="n" rel="next">The map between BIOS drives and OS devices</a>, Previous: <a href="#Installing-GRUB-using-grub2_002dinstall" accesskey="p" rel="prev">Installing GRUB using grub2-install</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Making-a-GRUB-bootable-CD_002dROM-1"><span>4.2 Making a GRUB bootable CD-ROM<a class="copiable-link" href="#Making-a-GRUB-bootable-CD_002dROM-1"> &para;</a></span></h3>

<p>GRUB supports the <em class="dfn">no emulation mode</em> in the El Torito
specification<a class="footnote" id="DOCF6" href="#FOOT6"><sup>6</sup></a>. This means that you can use the whole CD-ROM
from GRUB and you don&rsquo;t have to make a floppy or hard disk image file,
which can cause compatibility problems.
</p>
<p>For booting from a CD-ROM, GRUB uses a special image called
<samp class="file">cdboot.img</samp>, which is concatenated with <samp class="file">core.img</samp>. The
<samp class="file">core.img</samp> used for this should be built with at least the
&lsquo;<samp class="samp">iso9660</samp>&rsquo; and &lsquo;<samp class="samp">biosdisk</samp>&rsquo; modules. Your bootable CD-ROM will
usually also need to include a configuration file <samp class="file">grub.cfg</samp> and some
other GRUB modules.
</p>
<p>To make a simple generic GRUB rescue CD, you can use the
<code class="command">grub2-mkrescue</code> program (see <a class="pxref" href="#Invoking-grub2_002dmkrescue">Invoking grub2-mkrescue</a>):
</p>
<div class="example">
<pre class="example-preformatted">$ <kbd class="kbd">grub2-mkrescue -o grub.iso</kbd>
</pre></div>

<p>You will often need to include other files in your image. To do this, first
make a top directory for the bootable image, say, &lsquo;<samp class="samp">iso</samp>&rsquo;:
</p>
<div class="example">
<pre class="example-preformatted">$ <kbd class="kbd">mkdir iso</kbd>
</pre></div>

<p>Make a directory for GRUB:
</p>
<div class="example">
<pre class="example-preformatted">$ <kbd class="kbd">mkdir -p iso/boot/grub</kbd>
</pre></div>

<p>If desired, make the config file <samp class="file">grub.cfg</samp> under <samp class="file">iso/boot/grub</samp>
(see <a class="pxref" href="#Configuration">Writing your own configuration file</a>), and copy any files and directories for the disc to the
directory <samp class="file">iso/</samp>.
</p>
<p>Finally, make the image:
</p>
<div class="example">
<pre class="example-preformatted">$ <kbd class="kbd">grub2-mkrescue -o grub.iso iso</kbd>
</pre></div>

<p>This produces a file named <samp class="file">grub.iso</samp>, which then can be burned
into a CD (or a DVD), or written to a USB mass storage device.
</p>
<p>The root device will be set up appropriately on entering your
<samp class="file">grub.cfg</samp> configuration file, so you can refer to file names on the CD
without needing to use an explicit device name. This makes it easier to
produce rescue images that will work on both optical drives and USB mass
storage devices.
</p>

<hr>
</div>
<div class="section-level-extent" id="Device-map">
<div class="nav-panel">
<p>
Next: <a href="#BIOS-installation" accesskey="n" rel="next">BIOS installation</a>, Previous: <a href="#Making-a-GRUB-bootable-CD_002dROM" accesskey="p" rel="prev">Making a GRUB bootable CD-ROM</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="The-map-between-BIOS-drives-and-OS-devices"><span>4.3 The map between BIOS drives and OS devices<a class="copiable-link" href="#The-map-between-BIOS-drives-and-OS-devices"> &para;</a></span></h3>

<p>If the device map file exists, the GRUB utilities (<code class="command">grub2-probe</code>,
etc.) read it to map BIOS drives to OS devices.  This file consists of lines
like this:
</p>
<div class="example">
<pre class="example-preformatted">(<var class="var">device</var>) <var class="var">file</var>
</pre></div>

<p><var class="var">device</var> is a drive specified in the GRUB syntax (see <a class="pxref" href="#Device-syntax">How to specify devices</a>), and <var class="var">file</var> is an OS file, which is normally a device file.
</p>
<p>Historically, the device map file was used because GRUB device names had to
be used in the configuration file, and they were derived from BIOS drive
numbers.  The map between BIOS drives and OS devices cannot always be
guessed correctly: for example, GRUB will get the order wrong if you
exchange the boot sequence between IDE and SCSI in your BIOS.
</p>
<p>Unfortunately, even OS device names are not always stable.  Modern versions
of the Linux kernel may probe drives in a different order from boot to boot,
and the prefix (<samp class="file">/dev/hd*</samp> versus <samp class="file">/dev/sd*</samp>) may change depending
on the driver subsystem in use.  As a result, the device map file required
frequent editing on some systems.
</p>
<p>GRUB avoids this problem nowadays by using UUIDs or file system labels when
generating <samp class="file">grub.cfg</samp>, and we advise that you do the same for any
custom menu entries you write.  If the device map file does not exist, then
the GRUB utilities will assume a temporary device map on the fly.  This is
often good enough, particularly in the common case of single-disk systems.
</p>
<p>However, the device map file is not entirely obsolete yet, and it is
used for overriding when current environment is different from the one on boot.
Most common case is if you use a partition or logical volume as a disk for
virtual machine.  You can put any comments in the file if needed,
as the GRUB utilities assume that a line is just a comment if
the first character is &lsquo;<samp class="samp">#</samp>&rsquo;.
</p>

<hr>
</div>
<div class="section-level-extent" id="BIOS-installation">
<div class="nav-panel">
<p>
Previous: <a href="#Device-map" accesskey="p" rel="prev">The map between BIOS drives and OS devices</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="BIOS-installation-1"><span>4.4 BIOS installation<a class="copiable-link" href="#BIOS-installation-1"> &para;</a></span></h3>

<p>The partition table format traditionally used on PC BIOS platforms is called
the Master Boot Record (MBR) format; this is the format that allows up to
four primary partitions and additional logical partitions.  With this
partition table format, there are two ways to install GRUB: it can be
embedded in the area between the MBR and the first partition (called by
various names, such as the &quot;boot track&quot;, &quot;MBR gap&quot;, or &quot;embedding area&quot;, and
which is usually at least 1000 KiB), or the core image can be installed in a
file system and a list of the blocks that make it up can be stored in the
first sector of that partition.
</p>
<p>Modern tools usually leave MBR gap of at least 1023 KiB. This amount is
sufficient to cover most configurations. Hence this value is recommended
by the GRUB team.
</p>
<p>Historically many tools left only 31 KiB of space. This is not enough to
parse reliably difficult structures like Btrfs, ZFS, RAID or LVM, or to
use difficult disk access methods like ahci. Hence GRUB will warn if attempted
to install into small MBR gap except in a small number of configurations
that were grandfathered. The grandfathered config must:
</p>
<ul class="itemize mark-bullet">
<li>use biosdisk as disk access module for <samp class="file">/boot</samp>

</li><li>not use any additional partition maps to access <samp class="file">/boot</samp>

</li><li><samp class="file">/boot</samp> must be on one of following filesystems:
   AFFS, AFS, BFS, cpio, newc, odc, ext2/3/4, FAT, exFAT,
   F2FS, HFS, uncompressed HFS+, ISO9660, JFS, Minix, Minix2, Minix3, NILFS2,
   NTFS, ReiserFS, ROMFS, SFS, tar, UDF, UFS1, UFS2, XFS
</li></ul>

<p>MBR gap has few technical problems.  There is no way to reserve space in
the embedding area with complete safety, and some proprietary software is
known to use it to make it difficult for users to work around licensing
restrictions. GRUB works around it by detecting sectors by other software and
avoiding them and protecting its own sectors using Reed-Solomon encoding.
</p>
<p>GRUB team recommends having MBR gap of at least 1000 KiB.
</p>
<p>Should it not be possible, GRUB has support for a fallback solution which is
heavily recommended against. Installing to a filesystem means that GRUB is
vulnerable to its blocks being moved around by filesystem features such as
tail packing, or even by aggressive fsck implementations, so this approach
is quite fragile; and this approach can only be used if the <samp class="file">/boot</samp>
filesystem is on the same disk that the BIOS boots from, so that GRUB does
not have to rely on guessing BIOS drive numbers.
</p>
<p>The GRUB development team generally recommends embedding GRUB before the
first partition, unless you have special requirements.  You must ensure that
the first partition starts at least 1000 KiB (2000 sectors) from the start of
the disk; on modern disks, it is often a performance advantage to align
partitions on larger boundaries anyway, so the first partition might start 1
MiB from the start of the disk.
</p>
<h3 class="heading" id="GPT"><span>GPT<a class="copiable-link" href="#GPT"> &para;</a></span></h3>

<p>Some newer systems use the GUID Partition Table (GPT) format.  This was
specified as part of the Extensible Firmware Interface (EFI), but it can
also be used on BIOS platforms if system software supports it; for example,
GRUB and GNU/Linux can be used in this configuration.  With this format, it
is possible to reserve a whole partition for GRUB, called the BIOS Boot
Partition.  GRUB can then be embedded into that partition without the risk
of being overwritten by other software and without being contained in a
filesystem which might move its blocks around.
</p>
<p>When creating a BIOS Boot Partition on a GPT system, you should make sure
that it is at least 31 KiB in size.  (GPT-formatted disks are not usually
particularly small, so we recommend that you make it larger than the bare
minimum, such as 1 MiB, to allow plenty of room for growth.)  You must also
make sure that it has the proper partition type.  Using GNU Parted, you can
set this using a command such as the following:
</p>
<div class="example">
<pre class="example-preformatted"># <kbd class="kbd">parted /dev/<var class="var">disk</var> set <var class="var">partition-number</var> bios_grub on</kbd>
</pre></div>

<p>If you are using gdisk, set the partition type to &lsquo;<samp class="samp">0xEF02</samp>&rsquo;.  With
partitioning programs that require setting the GUID directly, it should be
&lsquo;<samp class="samp">21686148-6449-6e6f-744e656564454649</samp>&rsquo;.
</p>
<p><strong class="strong">Caution:</strong> Be very careful which partition you select!  When GRUB
finds a BIOS Boot Partition during installation, it will automatically
overwrite part of it.  Make sure that the partition does not contain any
other data.
</p>

<hr>
</div>
</div>
<div class="chapter-level-extent" id="Booting">
<div class="nav-panel">
<p>
Next: <a href="#Configuration" accesskey="n" rel="next">Writing your own configuration file</a>, Previous: <a href="#Installation" accesskey="p" rel="prev">Installation</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Booting-1"><span>5 Booting<a class="copiable-link" href="#Booting-1"> &para;</a></span></h2>

<p>GRUB can load Multiboot-compliant kernels in a consistent way,
but for some free operating systems you need to use some OS-specific
magic.
</p>

<ul class="mini-toc">
<li><a href="#General-boot-methods" accesskey="1">How to boot operating systems</a></li>
<li><a href="#Loopback-booting" accesskey="2">Loopback booting</a></li>
<li><a href="#LVM-cache-booting" accesskey="3">Booting from LVM cache logical volume</a></li>
<li><a href="#OS_002dspecific-notes" accesskey="4">Some caveats on OS-specific issues</a></li>
</ul>
<hr>
<div class="section-level-extent" id="General-boot-methods">
<div class="nav-panel">
<p>
Next: <a href="#Loopback-booting" accesskey="n" rel="next">Loopback booting</a>, Up: <a href="#Booting" accesskey="u" rel="up">Booting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="How-to-boot-operating-systems"><span>5.1 How to boot operating systems<a class="copiable-link" href="#How-to-boot-operating-systems"> &para;</a></span></h3>

<p>GRUB has three distinct boot methods: loading an operating system
directly, using kexec from userspace, and chainloading another
bootloader. Generally speaking, the first two are more desirable
because you don&rsquo;t need to install or maintain other boot loaders and
GRUB is flexible enough to load an operating system from an arbitrary
disk/partition. However, chainloading is sometimes required, as GRUB
doesn&rsquo;t support all existing operating systems natively.
</p>

<ul class="mini-toc">
<li><a href="#Loading-an-operating-system-directly" accesskey="1">How to boot an OS directly with GRUB</a></li>
<li><a href="#Kexec" accesskey="2">Kexec with grub2-emu</a></li>
<li><a href="#Chain_002dloading" accesskey="3">Chain-loading an OS</a></li>
</ul>
<hr>
<div class="subsection-level-extent" id="Loading-an-operating-system-directly">
<div class="nav-panel">
<p>
Next: <a href="#Kexec" accesskey="n" rel="next">Kexec with grub2-emu</a>, Up: <a href="#General-boot-methods" accesskey="u" rel="up">How to boot operating systems</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="How-to-boot-an-OS-directly-with-GRUB"><span>5.1.1 How to boot an OS directly with GRUB<a class="copiable-link" href="#How-to-boot-an-OS-directly-with-GRUB"> &para;</a></span></h4>

<p>Multiboot (see <a data-manual="multiboot" href="https://www.gnu.org/software/grub/manual//multiboot/multiboot.html#Top">Motivation</a> in <cite class="cite">The Multiboot Specification</cite>) is the native format supported by GRUB.
For the sake of convenience, there is also support for Linux, FreeBSD,
NetBSD and OpenBSD. If you want to boot other operating systems, you
will have to chain-load them (see <a class="pxref" href="#Chain_002dloading">Chain-loading an OS</a>).
</p>
<p>FIXME: this section is incomplete.
</p>
<ol class="enumerate">
<li> Run the command <code class="command">boot</code> (see <a class="pxref" href="#boot">boot</a>).
</li></ol>

<p>However, DOS and Windows have some deficiencies, so you might have to
use more complicated instructions. See <a class="xref" href="#DOS_002fWindows">DOS/Windows</a>, for more
information.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="Kexec">
<div class="nav-panel">
<p>
Next: <a href="#Chain_002dloading" accesskey="n" rel="next">Chain-loading an OS</a>, Previous: <a href="#Loading-an-operating-system-directly" accesskey="p" rel="prev">How to boot an OS directly with GRUB</a>, Up: <a href="#General-boot-methods" accesskey="u" rel="up">How to boot operating systems</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="Kexec-with-grub2_002demu"><span>5.1.2 Kexec with grub2-emu<a class="copiable-link" href="#Kexec-with-grub2_002demu"> &para;</a></span></h4>

<p>GRUB can be run in userspace by invoking the grub2-emu tool. It will
read all configuration scripts as if booting directly (see <a class="ref" href="#Loading-an-operating-system-directly">How to boot an OS directly with GRUB</a>). With the <code class="code">--kexec</code> flag, and
kexec(8) support from the operating system, the <code class="command">linux</code> command
will directly boot the target image. For systems that lack working
systemctl(1) support for kexec, passing the <code class="code">--kexec</code> flag twice
will fallback to invoking kexec(8) directly; note however that this
fallback may be unsafe outside read-only environments, as it does not
invoke shutdown machinery.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="Chain_002dloading">
<div class="nav-panel">
<p>
Previous: <a href="#Kexec" accesskey="p" rel="prev">Kexec with grub2-emu</a>, Up: <a href="#General-boot-methods" accesskey="u" rel="up">How to boot operating systems</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="Chain_002dloading-an-OS"><span>5.1.3 Chain-loading an OS<a class="copiable-link" href="#Chain_002dloading-an-OS"> &para;</a></span></h4>

<p>Operating systems that do not support Multiboot and do not have specific
support in GRUB (specific support is available for Linux, FreeBSD, NetBSD
and OpenBSD) must be chain-loaded, which involves loading another boot
loader and jumping to it in real mode or via the firmware.
</p>
<p>The <code class="command">chainloader</code> command (see <a class="pxref" href="#chainloader">chainloader</a>) is used to set this
up.  It is normally also necessary to load some GRUB modules and set the
appropriate root device.  Putting this together, we get something like this,
for a Windows system on the first partition of the first hard disk:
</p>
<pre class="verbatim">menuentry &quot;Windows&quot; {
	insmod chain
	insmod ntfs
	set root=(hd0,1)
	chainloader +1
}
</pre>
<p>On systems with multiple hard disks, an additional workaround may be
required.  See <a class="xref" href="#DOS_002fWindows">DOS/Windows</a>.
</p>
<p>Chain-loading is only supported on PC BIOS and EFI platforms.
</p>
<hr>
</div>
</div>
<div class="section-level-extent" id="Loopback-booting">
<div class="nav-panel">
<p>
Next: <a href="#LVM-cache-booting" accesskey="n" rel="next">Booting from LVM cache logical volume</a>, Previous: <a href="#General-boot-methods" accesskey="p" rel="prev">How to boot operating systems</a>, Up: <a href="#Booting" accesskey="u" rel="up">Booting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Loopback-booting-1"><span>5.2 Loopback booting<a class="copiable-link" href="#Loopback-booting-1"> &para;</a></span></h3>
<p>GRUB is able to read from an image (be it one of CD or HDD) stored on
any of its accessible storages (refer to see <a class="pxref" href="#loopback">loopback</a> command).
However the OS itself should be able to find its root. This usually
involves running a userspace program running before the real root
is discovered. This is achieved by GRUB loading a specially made
small image and passing it as ramdisk to the kernel. This is achieved
by commands <code class="command">kfreebsd_module</code>, <code class="command">knetbsd_module_elf</code>,
<code class="command">kopenbsd_ramdisk</code>, <code class="command">initrd</code> (see <a class="pxref" href="#initrd">initrd</a>),
<code class="command">initrd16</code> (see <a class="pxref" href="#initrd16">initrd16</a>), <code class="command">multiboot_module</code>,
<code class="command">multiboot2_module</code> or <code class="command">xnu_ramdisk</code>
depending on the loader. Note that for knetbsd the image must be put
inside miniroot.kmod and the whole miniroot.kmod has to be loaded. In
kopenbsd payload this is disabled by default. Additionally, behaviour of
initial ramdisk depends on command line options. Several distributors provide
the image for this purpose or it&rsquo;s integrated in their standard ramdisk and
activated by special option. Consult your kernel and distribution manual for
more details. Other loaders like <code class="command">appleloader</code>, <code class="command">chainloader</code>
(BIOS, EFI, coreboot), <code class="command">freedos</code>, <code class="command">ntldr</code>, <code class="command">plan9</code>
and <code class="command">truecrypt</code> provide no possibility of loading initial ramdisk and
as far as author is aware the payloads in question don&rsquo;t support either initial
ramdisk or discovering loopback boot in other way and as such not bootable this
way. Please consider alternative boot methods like copying all files
from the image to actual partition. Consult your OS documentation for
more details.
</p>
<hr>
</div>
<div class="section-level-extent" id="LVM-cache-booting">
<div class="nav-panel">
<p>
Next: <a href="#OS_002dspecific-notes" accesskey="n" rel="next">Some caveats on OS-specific issues</a>, Previous: <a href="#Loopback-booting" accesskey="p" rel="prev">Loopback booting</a>, Up: <a href="#Booting" accesskey="u" rel="up">Booting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Booting-from-LVM-cache-logical-volume"><span>5.3 Booting from LVM cache logical volume<a class="copiable-link" href="#Booting-from-LVM-cache-logical-volume"> &para;</a></span></h3>

<p>The LVM cache logical volume is the logical volume consisting of the original
and the cache pool logical volume. The original is usually on a larger and
slower storage device while the cache pool is on a smaller and faster one. The
performance of the original volume can be improved by storing the frequently
used data on the cache pool to utilize the greater performance of faster
device.
</p>
<p>GRUB boots from LVM cache logical volume merely by reading it&rsquo;s original
logical volume so that dirty data in cache pool volume is disregarded. This is
not a problem for &quot;writethrough&quot; cache mode as it ensures that any data written
will be stored both on the cache and the origin LV. For the other cache mode
&quot;writeback&quot;, which delays writing from the cache pool back to the origin LV to
boost performance, GRUB may fail to boot in the wake of accidental power outage
due to it&rsquo;s inability to assemble the cache device for reading the required
dirty data left behind. The situation will be improved after adding full
support to the LVM cache logical volume in the future.
</p>
<hr>
</div>
<div class="section-level-extent" id="OS_002dspecific-notes">
<div class="nav-panel">
<p>
Previous: <a href="#LVM-cache-booting" accesskey="p" rel="prev">Booting from LVM cache logical volume</a>, Up: <a href="#Booting" accesskey="u" rel="up">Booting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Some-caveats-on-OS_002dspecific-issues"><span>5.4 Some caveats on OS-specific issues<a class="copiable-link" href="#Some-caveats-on-OS_002dspecific-issues"> &para;</a></span></h3>

<p>Here, we describe some caveats on several operating systems.
</p>

<ul class="mini-toc">
<li><a href="#GNU_002fHurd" accesskey="1">GNU/Hurd</a></li>
<li><a href="#GNU_002fLinux" accesskey="2">GNU/Linux</a></li>
<li><a href="#NetBSD" accesskey="3">NetBSD</a></li>
<li><a href="#DOS_002fWindows" accesskey="4">DOS/Windows</a></li>
</ul>
<hr>
<div class="subsection-level-extent" id="GNU_002fHurd">
<div class="nav-panel">
<p>
Next: <a href="#GNU_002fLinux" accesskey="n" rel="next">GNU/Linux</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">Some caveats on OS-specific issues</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="GNU_002fHurd-1"><span>5.4.1 GNU/Hurd<a class="copiable-link" href="#GNU_002fHurd-1"> &para;</a></span></h4>

<p>Since GNU/Hurd is Multiboot-compliant, it is easy to boot it; there is
nothing special about it. But do not forget that you have to specify a
root partition to the kernel.
</p>
<ol class="enumerate">
<li> Set GRUB&rsquo;s root device to the same drive as GNU/Hurd&rsquo;s.  The command
<code class="code">search --set=root --file /boot/gnumach.gz</code> or similar may help you
(see <a class="pxref" href="#search">search</a>).

</li><li> Load the kernel and the modules, like this:

<div class="example">
<div class="group"><pre class="example-preformatted">grub&gt; <kbd class="kbd">multiboot /boot/gnumach.gz root=device:hd0s1</kbd>
grub&gt; <kbd class="kbd">module  /hurd/ext2fs.static ext2fs --readonly \
                   --multiboot-command-line='${kernel-command-line}' \
                   --host-priv-port='${host-port}' \
                   --device-master-port='${device-port}' \
                   --exec-server-task='${exec-task}' -T typed '${root}' \
                   '$(task-create)' '$(task-resume)'</kbd>
grub&gt; <kbd class="kbd">module /lib/ld.so.1 exec /hurd/exec '$(exec-task=task-create)'</kbd>
</pre></div></div>

</li><li> Finally, run the command <code class="command">boot</code> (see <a class="pxref" href="#boot">boot</a>).
</li></ol>

<hr>
</div>
<div class="subsection-level-extent" id="GNU_002fLinux">
<div class="nav-panel">
<p>
Next: <a href="#NetBSD" accesskey="n" rel="next">NetBSD</a>, Previous: <a href="#GNU_002fHurd" accesskey="p" rel="prev">GNU/Hurd</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">Some caveats on OS-specific issues</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="GNU_002fLinux-1"><span>5.4.2 GNU/Linux<a class="copiable-link" href="#GNU_002fLinux-1"> &para;</a></span></h4>

<p>It is relatively easy to boot GNU/Linux from GRUB, because it somewhat
resembles to boot a Multiboot-compliant OS.
</p>
<ol class="enumerate">
<li> Set GRUB&rsquo;s root device to the same drive as GNU/Linux&rsquo;s.  The command
<code class="code">search --set=root --file /vmlinuz</code> or similar may help you
(see <a class="pxref" href="#search">search</a>).

</li><li> Load the kernel using the command <code class="command">linux</code> (see <a class="pxref" href="#linux">linux</a>):

<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">linux /vmlinuz root=/dev/sda1</kbd>
</pre></div>

<p>If you need to specify some kernel parameters, just append them to the
command.  For example, to set <samp class="option">acpi</samp> to &lsquo;<samp class="samp">off</samp>&rsquo;, do this:
</p>
<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">linux /vmlinuz root=/dev/sda1 acpi=off</kbd>
</pre></div>

<p>See the documentation in the Linux source tree for complete information on
the available options.
</p>
<p>With <code class="command">linux</code> GRUB uses 32-bit protocol. Some BIOS services like APM
or EDD aren&rsquo;t available with this protocol. In this case you need to use
<code class="command">linux16</code>
</p>
<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">linux16 /vmlinuz root=/dev/sda1 acpi=off</kbd>
</pre></div>

</li><li> If you use an initrd, execute the command <code class="command">initrd</code> (see <a class="pxref" href="#initrd">initrd</a>)
after <code class="command">linux</code>:

<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">initrd /initrd</kbd>
</pre></div>

<p>If you used <code class="command">linux16</code> you need to use <code class="command">initrd16</code>:
</p>
<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">initrd16 /initrd</kbd>
</pre></div>

</li><li> Finally, run the command <code class="command">boot</code> (see <a class="pxref" href="#boot">boot</a>).
</li></ol>

<hr>
</div>
<div class="subsection-level-extent" id="NetBSD">
<div class="nav-panel">
<p>
Next: <a href="#DOS_002fWindows" accesskey="n" rel="next">DOS/Windows</a>, Previous: <a href="#GNU_002fLinux" accesskey="p" rel="prev">GNU/Linux</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">Some caveats on OS-specific issues</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="NetBSD-1"><span>5.4.3 NetBSD<a class="copiable-link" href="#NetBSD-1"> &para;</a></span></h4>

<p>Booting a NetBSD kernel from GRUB is also relatively easy: first set
GRUB&rsquo;s root device, then load the kernel and the modules, and finally
run <code class="command">boot</code>.
</p>
<ol class="enumerate">
<li> Set GRUB&rsquo;s root device to the partition holding the NetBSD root file
system.  For a disk with a NetBSD disk label, this is usually the first
partition (a:).  In that case, and assuming that the partition is on the
first hard disk, set GRUB&rsquo;s root device as follows:

<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">insmod part_bsd</kbd>
grub&gt; <kbd class="kbd">set root=(hd0,netbsd1)</kbd>
</pre></div>

<p>For a disk with a GUID Partition Table (GPT), and assuming that the
NetBSD root partition is the third GPT partition, do this:
</p>
<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">insmod part_gpt</kbd>
grub&gt; <kbd class="kbd">set root=(hd0,gpt3)</kbd>
</pre></div>

</li><li> Load the kernel using the command <code class="command">knetbsd</code>:

<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">knetbsd /netbsd</kbd>
</pre></div>

<p>Various options may be given to <code class="command">knetbsd</code>.  These options are,
for the most part, the same as in the NetBSD boot loader.  For instance,
to boot the system in single-user mode and with verbose messages, do
this:
</p>
<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">knetbsd /netbsd -s -v</kbd>
</pre></div>

</li><li> If needed, load kernel modules with the command
<code class="command">knetbsd_module_elf</code>.  A typical example is the module for the
root file system:

<div class="example">
<pre class="example-preformatted">grub&gt; <kbd class="kbd">knetbsd_module_elf /stand/amd64/6.0/modules/ffs/ffs.kmod</kbd>
</pre></div>

</li><li> Finally, run the command <code class="command">boot</code> (see <a class="pxref" href="#boot">boot</a>).
</li></ol>

<hr>
</div>
<div class="subsection-level-extent" id="DOS_002fWindows">
<div class="nav-panel">
<p>
Previous: <a href="#NetBSD" accesskey="p" rel="prev">NetBSD</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">Some caveats on OS-specific issues</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="DOS_002fWindows-1"><span>5.4.4 DOS/Windows<a class="copiable-link" href="#DOS_002fWindows-1"> &para;</a></span></h4>

<p>GRUB cannot boot DOS or Windows directly, so you must chain-load them
(see <a class="pxref" href="#Chain_002dloading">Chain-loading an OS</a>). However, their boot loaders have some critical
deficiencies, so it may not work to just chain-load them. To overcome
the problems, GRUB provides you with two helper functions.
</p>
<p>If you have installed DOS (or Windows) on a non-first hard disk, you
have to use the disk swapping technique, because that OS cannot boot
from any disks but the first one. The workaround used in GRUB is the
command <code class="command">drivemap</code> (see <a class="pxref" href="#drivemap">drivemap</a>), like this:
</p>
<div class="example">
<pre class="example-preformatted">drivemap -s (hd0) (hd1)
</pre></div>

<p>This performs a <em class="dfn">virtual</em> swap between your first and second hard
drive.
</p>
<p><strong class="strong">Caution:</strong> This is effective only if DOS (or Windows) uses BIOS
to access the swapped disks. If that OS uses a special driver for the
disks, this probably won&rsquo;t work.
</p>
<p>Another problem arises if you installed more than one set of DOS/Windows
onto one disk, because they could be confused if there are more than one
primary partitions for DOS/Windows. Certainly you should avoid doing
this, but there is a solution if you do want to do so. Use the partition
hiding/unhiding technique.
</p>
<p>If GRUB <em class="dfn">hides</em> a DOS (or Windows) partition (see <a class="pxref" href="#parttool">parttool</a>), DOS (or
Windows) will ignore the partition. If GRUB <em class="dfn">unhides</em> a DOS (or Windows)
partition, DOS (or Windows) will detect the partition. Thus, if you have
installed DOS (or Windows) on the first and the second partition of the
first hard disk, and you want to boot the copy on the first partition, do
the following:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">parttool (hd0,1) hidden-
parttool (hd0,2) hidden+
set root=(hd0,1)
chainloader +1
parttool <code class="verb">${root}</code> boot+
boot
</pre></div></div>

<hr>
</div>
</div>
</div>
<div class="chapter-level-extent" id="Configuration">
<div class="nav-panel">
<p>
Next: <a href="#Theme-file-format" accesskey="n" rel="next">Theme file format</a>, Previous: <a href="#Booting" accesskey="p" rel="prev">Booting</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Writing-your-own-configuration-file"><span>6 Writing your own configuration file<a class="copiable-link" href="#Writing-your-own-configuration-file"> &para;</a></span></h2>

<p>GRUB is configured using <samp class="file">grub.cfg</samp>, usually located under
<samp class="file">/boot/grub</samp>.  This file is quite flexible, but most users will not
need to write the whole thing by hand.
</p>

<ul class="mini-toc">
<li><a href="#Simple-configuration" accesskey="1">Simple configuration handling</a></li>
<li><a href="#Root-Identifcation-Heuristics" accesskey="2">Root Identifcation Heuristics</a></li>
<li><a href="#Shell_002dlike-scripting" accesskey="3">Writing full configuration files directly</a></li>
<li><a href="#Multi_002dboot-manual-config" accesskey="4">Multi-boot manual config</a></li>
<li><a href="#Embedded-configuration" accesskey="5">Embedding a configuration file into GRUB</a></li>
</ul>
<hr>
<div class="section-level-extent" id="Simple-configuration">
<div class="nav-panel">
<p>
Next: <a href="#Root-Identifcation-Heuristics" accesskey="n" rel="next">Root Identifcation Heuristics</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Writing your own configuration file</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Simple-configuration-handling"><span>6.1 Simple configuration handling<a class="copiable-link" href="#Simple-configuration-handling"> &para;</a></span></h3>

<p>The program <code class="command">grub2-mkconfig</code> (see <a class="pxref" href="#Invoking-grub2_002dmkconfig">Invoking grub2-mkconfig</a>)
generates <samp class="file">grub.cfg</samp> files suitable for most cases.  It is suitable for
use when upgrading a distribution, and will discover available kernels and
attempt to generate menu entries for them.
</p>
<p><code class="command">grub2-mkconfig</code> does have some limitations.  While adding extra
custom menu entries to the end of the list can be done by editing
<samp class="file">/etc/grub.d/40_custom</samp> or creating <samp class="file">/boot/grub2/custom.cfg</samp>,
changing the order of menu entries or changing their titles may require
making complex changes to shell scripts stored in <samp class="file">/etc/grub.d/</samp>.  This
may be improved in the future.  In the meantime, those who feel that it
would be easier to write <samp class="file">grub.cfg</samp> directly are encouraged to do so
(see <a class="pxref" href="#Booting">Booting</a>, and <a class="ref" href="#Shell_002dlike-scripting">Writing full configuration files directly</a>), and to disable any system
provided by their distribution to automatically run <code class="command">grub2-mkconfig</code>.
</p>
<p>The file <samp class="file">/etc/default/grub</samp> controls the operation of
<code class="command">grub2-mkconfig</code>.  It is sourced by a shell script, and so must be
valid POSIX shell input; normally, it will just be a sequence of
&lsquo;<samp class="samp">KEY=value</samp>&rsquo; lines, but if the value contains spaces or other special
characters then it must be quoted.  For example:
</p>
<div class="example">
<pre class="example-preformatted">GRUB_TERMINAL_INPUT=&quot;console serial&quot;
</pre></div>

<p>Valid keys in <samp class="file">/etc/default/grub</samp> are as follows:
</p>
<dl class="table">
<dt>&lsquo;<samp class="samp">GRUB_DEFAULT</samp>&rsquo;</dt>
<dd><p>The default menu entry.  This may be a number, in which case it identifies
the Nth entry in the generated menu counted from zero, or the title of a
menu entry, or the special string &lsquo;<samp class="samp">saved</samp>&rsquo;.  Using the id may be
useful if you want to set a menu entry as the default even though there may
be a variable number of entries before it.
</p>
<p>For example, if you have:
</p>
<pre class="verbatim">menuentry 'Example GNU/Linux distribution' --class gnu-linux --id example-gnu-linux {
	...
}
</pre>
<p>then you can make this the default using:
</p>
<div class="example">
<pre class="example-preformatted">GRUB_DEFAULT=example-gnu-linux
</pre></div>

<p>Previously it was documented the way to use entry title. While this still
works it&rsquo;s not recommended since titles often contain unstable device names
and may be translated
</p>
<p>If you set this to &lsquo;<samp class="samp">saved</samp>&rsquo;, then the default menu entry will be that
saved by &lsquo;<samp class="samp">GRUB_SAVEDEFAULT</samp>&rsquo; or <code class="command">grub2-set-default</code>.  This relies on
the environment block, which may not be available in all situations
(see <a class="pxref" href="#Environment-block">The GRUB environment block</a>).
</p>
<p>The default is &lsquo;<samp class="samp">0</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_SAVEDEFAULT</samp>&rsquo;</dt>
<dd><p>If this option is set to &lsquo;<samp class="samp">true</samp>&rsquo;, then, when an entry is selected, save
it as a new default entry for use by future runs of GRUB.  This is only
useful if &lsquo;<samp class="samp">GRUB_DEFAULT=saved</samp>&rsquo;; it is a separate option because
&lsquo;<samp class="samp">GRUB_DEFAULT=saved</samp>&rsquo; is useful without this option, in conjunction with
<code class="command">grub2-set-default</code>.  Unset by default.
This option relies on the environment block, which may not be available in
all situations (see <a class="pxref" href="#Environment-block">The GRUB environment block</a>).
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_TIMEOUT</samp>&rsquo;</dt>
<dd><p>Boot the default entry this many seconds after the menu is displayed, unless
a key is pressed.  The default is &lsquo;<samp class="samp">5</samp>&rsquo;.  Set to &lsquo;<samp class="samp">0</samp>&rsquo; to boot
immediately without displaying the menu, or to &lsquo;<samp class="samp">-1</samp>&rsquo; to wait
indefinitely.
</p>
<p>If &lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE</samp>&rsquo; is set to &lsquo;<samp class="samp">countdown</samp>&rsquo; or &lsquo;<samp class="samp">hidden</samp>&rsquo;,
the timeout is instead counted before the menu is displayed.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE</samp>&rsquo;</dt>
<dd><p>If this option is unset or set to &lsquo;<samp class="samp">menu</samp>&rsquo;, then GRUB will display the
menu and then wait for the timeout set by &lsquo;<samp class="samp">GRUB_TIMEOUT</samp>&rsquo; to expire
before booting the default entry.  Pressing a key interrupts the timeout.
</p>
<p>If this option is set to &lsquo;<samp class="samp">countdown</samp>&rsquo; or &lsquo;<samp class="samp">hidden</samp>&rsquo;, then, before
displaying the menu, GRUB will wait for the timeout set by &lsquo;<samp class="samp">GRUB_TIMEOUT</samp>&rsquo;
to expire.  If <kbd class="key">ESC</kbd> or <kbd class="key">F4</kbd> are pressed, or <kbd class="key">SHIFT</kbd> is held down
during that time, it will display the menu and wait for input.  If a hotkey
associated with a menu entry is pressed, it will boot the associated menu entry
immediately. If the timeout expires before either of these happens, it will
boot the default entry.  In the &lsquo;<samp class="samp">countdown</samp>&rsquo; case, it will show a one-line
indication of the remaining time.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_DEFAULT_BUTTON</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_TIMEOUT_BUTTON</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE_BUTTON</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_BUTTON_CMOS_ADDRESS</samp>&rsquo;</dt>
<dd><p>Variants of the corresponding variables without the &lsquo;<samp class="samp">_BUTTON</samp>&rsquo; suffix,
used to support vendor-specific power buttons.  See <a class="xref" href="#Vendor-power_002don-keys">Using GRUB with vendor power-on keys</a>.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_DISTRIBUTOR</samp>&rsquo;</dt>
<dd><p>Set by distributors of GRUB to their identifying name.  This is used to
generate more informative menu entry titles.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_TERMINAL_INPUT</samp>&rsquo;</dt>
<dd><p>Select the terminal input device.  You may select multiple devices here,
separated by spaces.
</p>
<p>Valid terminal input names depend on the platform, but may include
&lsquo;<samp class="samp">console</samp>&rsquo; (native platform console), &lsquo;<samp class="samp">serial</samp>&rsquo; (serial terminal),
&lsquo;<samp class="samp">serial_&lt;port&gt;</samp>&rsquo; (serial terminal with explicit port selection),
&lsquo;<samp class="samp">at_keyboard</samp>&rsquo; (PC AT keyboard), or &lsquo;<samp class="samp">usb_keyboard</samp>&rsquo; (USB keyboard
using the HID Boot Protocol, for cases where the firmware does not handle
this).
</p>
<p>The default is to use the platform&rsquo;s native terminal input.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_TERMINAL_OUTPUT</samp>&rsquo;</dt>
<dd><p>Select the terminal output device.  You may select multiple devices here,
separated by spaces.
</p>
<p>Valid terminal output names depend on the platform, but may include
&lsquo;<samp class="samp">console</samp>&rsquo; (native platform console), &lsquo;<samp class="samp">serial</samp>&rsquo; (serial terminal),
&lsquo;<samp class="samp">serial_&lt;port&gt;</samp>&rsquo; (serial terminal with explicit port selection),
&lsquo;<samp class="samp">gfxterm</samp>&rsquo; (graphics-mode output), &lsquo;<samp class="samp">vga_text</samp>&rsquo; (VGA text output),
&lsquo;<samp class="samp">mda_text</samp>&rsquo; (MDA text output), &lsquo;<samp class="samp">morse</samp>&rsquo; (Morse-coding using system
beeper) or &lsquo;<samp class="samp">spkmodem</samp>&rsquo; (simple data protocol using system speaker).
</p>
<p>&lsquo;<samp class="samp">spkmodem</samp>&rsquo; is useful when no serial port is available. Connect the output
of sending system (where GRUB is running) to line-in of receiving system
(usually developer machine).
On receiving system compile &lsquo;<samp class="samp">spkmodem-recv</samp>&rsquo; from
&lsquo;<samp class="samp">util/spkmodem-recv.c</samp>&rsquo; and run:
</p>
<div class="example">
<pre class="example-preformatted">parecord --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv
</pre></div>

<p>The default is to use the platform&rsquo;s native terminal output.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_TERMINAL</samp>&rsquo;</dt>
<dd><p>If this option is set, it overrides both &lsquo;<samp class="samp">GRUB_TERMINAL_INPUT</samp>&rsquo; and
&lsquo;<samp class="samp">GRUB_TERMINAL_OUTPUT</samp>&rsquo; to the same value.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_SERIAL_COMMAND</samp>&rsquo;</dt>
<dd><p>A command to configure the serial port when using the serial console.
See <a class="xref" href="#serial">serial</a>.  Defaults to &lsquo;<samp class="samp">serial</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_LINUX</samp>&rsquo;</dt>
<dd><p>Command-line arguments to add to menu entries for the Linux kernel.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_LINUX_DEFAULT</samp>&rsquo;</dt>
<dd><p>Unless &lsquo;<samp class="samp">GRUB_DISABLE_RECOVERY</samp>&rsquo; is set to &lsquo;<samp class="samp">true</samp>&rsquo;, two menu
entries will be generated for each Linux kernel: one default entry and one
entry for recovery mode.  This option lists command-line arguments to add
only to the default menu entry, after those listed in
&lsquo;<samp class="samp">GRUB_CMDLINE_LINUX</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_LINUX_RECOVERY</samp>&rsquo;</dt>
<dd><p>Unless &lsquo;<samp class="samp">GRUB_DISABLE_RECOVERY</samp>&rsquo; is set to &lsquo;<samp class="samp">true</samp>&rsquo;, two menu
entries will be generated for each Linux kernel: one default entry and one
entry for recovery mode. This option lists command-line arguments to add
only to the recovery menu entry, before those listed in &lsquo;<samp class="samp">GRUB_CMDLINE_LINUX</samp>&rsquo;.
The default is &lsquo;<samp class="samp">single</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_NETBSD</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_NETBSD_DEFAULT</samp>&rsquo;</dt>
<dd><p>As &lsquo;<samp class="samp">GRUB_CMDLINE_LINUX</samp>&rsquo; and &lsquo;<samp class="samp">GRUB_CMDLINE_LINUX_DEFAULT</samp>&rsquo;, but for
NetBSD.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_GNUMACH</samp>&rsquo;</dt>
<dd><p>As &lsquo;<samp class="samp">GRUB_CMDLINE_LINUX</samp>&rsquo;, but for GNU Mach.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_XEN</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_XEN_DEFAULT</samp>&rsquo;</dt>
<dd><p>The values of these options are passed to Xen hypervisor Xen menu entries,
for all respectively normal entries.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_LINUX_XEN_REPLACE</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT</samp>&rsquo;</dt>
<dd><p>The values of these options replace the values of &lsquo;<samp class="samp">GRUB_CMDLINE_LINUX</samp>&rsquo;
and &lsquo;<samp class="samp">GRUB_CMDLINE_LINUX_DEFAULT</samp>&rsquo; for Linux and Xen menu entries.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_TOP_LEVEL</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_TOP_LEVEL_XEN</samp>&rsquo;</dt>
<dd><p>This option should be an absolute path to a kernel image. If provided, the
image specified will be made the top-level entry if it is found in the scan.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_TOP_LEVEL_OS_PROBER</samp>&rsquo;</dt>
<dd><p>This option should be a line of output from <code class="command">os-prober</code>. As
&lsquo;<samp class="samp">GRUB_TOP_LEVEL</samp>&rsquo;, if provided, the image specified will be made the
top-level entry if it is found in the scan.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_EARLY_INITRD_LINUX_CUSTOM</samp>&rsquo;</dt>
<dt>&lsquo;<samp class="samp">GRUB_EARLY_INITRD_LINUX_STOCK</samp>&rsquo;</dt>
<dd><p>List of space-separated early initrd images to be loaded from &lsquo;<samp class="samp">/boot</samp>&rsquo;.
This is for loading things like CPU microcode, firmware, ACPI tables, crypto
keys, and so on. These early images will be loaded in the order declared,
and all will be loaded before the actual functional initrd image.
</p>
<p>&lsquo;<samp class="samp">GRUB_EARLY_INITRD_LINUX_STOCK</samp>&rsquo; is for your distribution to declare
images that are provided by the distribution. It should not be modified
without understanding the consequences. They will be loaded first.
</p>
<p>&lsquo;<samp class="samp">GRUB_EARLY_INITRD_LINUX_CUSTOM</samp>&rsquo; is for your custom created images.
</p>
<p>The default stock images are as follows, though they may be overridden by
your distribution:
</p><div class="example">
<pre class="example-preformatted">intel-uc.img intel-ucode.img amd-uc.img amd-ucode.img early_ucode.cpio microcode.cpio
</pre></div>

</dd>
<dt>&lsquo;<samp class="samp">GRUB_DISABLE_LINUX_UUID</samp>&rsquo;</dt>
<dd><p>Normally, <code class="command">grub2-mkconfig</code> will generate menu entries that use
universally-unique identifiers (UUIDs) to identify the root filesystem to
the Linux kernel, using a &lsquo;<samp class="samp">root=UUID=...</samp>&rsquo; kernel parameter.  This is
usually more reliable, but in some cases it may not be appropriate.  To
disable the use of UUIDs, set this option to &lsquo;<samp class="samp">true</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo;</dt>
<dd><p>If <code class="command">grub2-mkconfig</code> cannot identify the root filesystem via its
universally-unique indentifier (UUID), <code class="command">grub2-mkconfig</code> can use the UUID
of the partition containing the filesystem to identify the root filesystem to
the Linux kernel via a &lsquo;<samp class="samp">root=PARTUUID=...</samp>&rsquo; kernel parameter.  This is not
as reliable as using the filesystem UUID, but is more reliable than using the
Linux device names. When &lsquo;<samp class="samp">GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; is set to
&lsquo;<samp class="samp">false</samp>&rsquo;, the Linux kernel version must be 2.6.37 (3.10 for systems using
the MSDOS partition scheme) or newer.  This option defaults to &lsquo;<samp class="samp">true</samp>&rsquo;.  To
enable the use of partition UUIDs, set this option to &lsquo;<samp class="samp">false</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_DISABLE_RECOVERY</samp>&rsquo;</dt>
<dd><p>If this option is set to &lsquo;<samp class="samp">true</samp>&rsquo;, disable the generation of recovery
mode menu entries.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_DISABLE_UUID</samp>&rsquo;</dt>
<dd><p>Normally, <code class="command">grub2-mkconfig</code> will generate menu entries that use
universally-unique identifiers (UUIDs) to identify various filesystems to
search for files.  This is usually more reliable, but in some cases it may
not be appropriate.  To disable this use of UUIDs, set this option to
&lsquo;<samp class="samp">true</samp>&rsquo;. Setting this option to &lsquo;<samp class="samp">true</samp>&rsquo;, will also set the options
&lsquo;<samp class="samp">GRUB_DISABLE_LINUX_UUID</samp>&rsquo; and &lsquo;<samp class="samp">GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; to
&lsquo;<samp class="samp">true</samp>&rsquo;, unless they have been explicilty set to &lsquo;<samp class="samp">false</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_VIDEO_BACKEND</samp>&rsquo;</dt>
<dd><p>If graphical video support is required, either because the &lsquo;<samp class="samp">gfxterm</samp>&rsquo;
graphical terminal is in use or because &lsquo;<samp class="samp">GRUB_GFXPAYLOAD_LINUX</samp>&rsquo; is set,
then <code class="command">grub2-mkconfig</code> will normally load all available GRUB video
drivers and use the one most appropriate for your hardware.  If you need to
override this for some reason, then you can set this option.
</p>
<p>After <code class="command">grub2-install</code> has been run, the available video drivers are
listed in <samp class="file">/boot/grub2/video.lst</samp>.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_GFXMODE</samp>&rsquo;</dt>
<dd><p>Set the resolution used on the &lsquo;<samp class="samp">gfxterm</samp>&rsquo; graphical terminal.  Note that
you can only use modes which your graphics card supports via VESA BIOS
Extensions (VBE), so for example native LCD panel resolutions may not be
available.  The default is &lsquo;<samp class="samp">auto</samp>&rsquo;, which tries to select a preferred
resolution.  See <a class="xref" href="#gfxmode">gfxmode</a>.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_BACKGROUND</samp>&rsquo;</dt>
<dd><p>Set a background image for use with the &lsquo;<samp class="samp">gfxterm</samp>&rsquo; graphical terminal.
The value of this option must be a file readable by GRUB at boot time, and
it must end with <samp class="file">.png</samp>, <samp class="file">.tga</samp>, <samp class="file">.jpg</samp>, or <samp class="file">.jpeg</samp>.
The image will be scaled if necessary to fit the screen. Image height and
width will be restricted by an artificial limit of 16384.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_THEME</samp>&rsquo;</dt>
<dd><p>Set a theme for use with the &lsquo;<samp class="samp">gfxterm</samp>&rsquo; graphical terminal.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_GFXPAYLOAD_LINUX</samp>&rsquo;</dt>
<dd><p>Set to &lsquo;<samp class="samp">text</samp>&rsquo; to force the Linux kernel to boot in normal text mode,
&lsquo;<samp class="samp">keep</samp>&rsquo; to preserve the graphics mode set using &lsquo;<samp class="samp">GRUB_GFXMODE</samp>&rsquo;,
&lsquo;<samp class="samp"><var class="var">width</var>x<var class="var">height</var></samp>&rsquo;[&lsquo;<samp class="samp">x<var class="var">depth</var></samp>&rsquo;] to set a particular
graphics mode, or a sequence of these separated by commas or semicolons to
try several modes in sequence.  See <a class="xref" href="#gfxpayload">gfxpayload</a>.
</p>
<p>Depending on your kernel, your distribution, your graphics card, and the
phase of the moon, note that using this option may cause GNU/Linux to suffer
from various display problems, particularly during the early part of the
boot sequence.  If you have problems, set this option to &lsquo;<samp class="samp">text</samp>&rsquo; and
GRUB will tell Linux to boot in normal text mode.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_DISABLE_OS_PROBER</samp>&rsquo;</dt>
<dd><p>Normally, <code class="command">grub2-mkconfig</code> will try to use the external
<code class="command">os-prober</code> program, if installed, to discover other operating
systems installed on the same system and generate appropriate menu entries
for them.  Set this option to &lsquo;<samp class="samp">true</samp>&rsquo; to disable this.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_OS_PROBER_SKIP_LIST</samp>&rsquo;</dt>
<dd><p>List of space-separated FS UUIDs of filesystems to be ignored from os-prober
output. For efi chainloaders it&rsquo;s &lt;UUID&gt;@&lt;EFI FILE&gt;
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_DISABLE_SUBMENU</samp>&rsquo;</dt>
<dd><p>Normally, <code class="command">grub2-mkconfig</code> will generate top level menu entry for
the kernel with highest version number and put all other found kernels
or alternative menu entries for recovery mode in submenu. For entries returned
by <code class="command">os-prober</code> first entry will be put on top level and all others
in submenu. If this option is set to &lsquo;<samp class="samp">true</samp>&rsquo;, flat menu with all entries
on top level will be generated instead. Changing this option will require
changing existing values of &lsquo;<samp class="samp">GRUB_DEFAULT</samp>&rsquo;, &lsquo;<samp class="samp">fallback</samp>&rsquo; (see <a class="pxref" href="#fallback">fallback</a>)
and &lsquo;<samp class="samp">default</samp>&rsquo; (see <a class="pxref" href="#default">default</a>) environment variables as well as saved
default entry using <code class="command">grub2-set-default</code> and value used with
<code class="command">grub2-reboot</code>.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_ENABLE_CRYPTODISK</samp>&rsquo;</dt>
<dd><p>If set to &lsquo;<samp class="samp">y</samp>&rsquo;, <code class="command">grub2-mkconfig</code> and <code class="command">grub2-install</code> will
check for encrypted disks and generate additional commands needed to access
them during boot.  Note that in this case unattended boot is not possible
because GRUB will wait for passphrase to unlock encrypted container.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_INIT_TUNE</samp>&rsquo;</dt>
<dd><p>Play a tune on the speaker when GRUB starts.  This is particularly useful
for users unable to see the screen.  The value of this option is passed
directly to <a class="ref" href="#play">play</a>.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_BADRAM</samp>&rsquo;</dt>
<dd><p>If this option is set, GRUB will issue a <a class="ref" href="#badram">badram</a> command to filter
out specified regions of RAM.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_PRELOAD_MODULES</samp>&rsquo;</dt>
<dd><p>This option may be set to a list of GRUB module names separated by spaces.
Each module will be loaded as early as possible, at the start of
<samp class="file">grub.cfg</samp>.
</p>
</dd>
</dl>

<p>The following options are still accepted for compatibility with existing
configurations, but have better replacements:
</p>
<dl class="table">
<dt>&lsquo;<samp class="samp">GRUB_HIDDEN_TIMEOUT</samp>&rsquo;</dt>
<dd><p>Wait this many seconds before displaying the menu.  If <kbd class="key">ESC</kbd> or <kbd class="key">F4</kbd> are
pressed, or <kbd class="key">SHIFT</kbd> is held down during that time, display the menu and wait
for input according to &lsquo;<samp class="samp">GRUB_TIMEOUT</samp>&rsquo;.  If a hotkey associated with a menu
entry is pressed, boot the associated menu entry immediately.  If the timeout
expires before either of these happens, display the menu for the number of
seconds specified in &lsquo;<samp class="samp">GRUB_TIMEOUT</samp>&rsquo; before booting the default entry.
</p>
<p>If you set &lsquo;<samp class="samp">GRUB_HIDDEN_TIMEOUT</samp>&rsquo;, you should also set
&lsquo;<samp class="samp">GRUB_TIMEOUT=0</samp>&rsquo; so that the menu is not displayed at all unless
<kbd class="key">ESC</kbd> or <kbd class="key">F4</kbd> are pressed, or <kbd class="key">SHIFT</kbd> is held down.
</p>
<p>This option is unset by default, and is deprecated in favour of the less
confusing &lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE=countdown</samp>&rsquo; or
&lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE=hidden</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_HIDDEN_TIMEOUT_QUIET</samp>&rsquo;</dt>
<dd><p>In conjunction with &lsquo;<samp class="samp">GRUB_HIDDEN_TIMEOUT</samp>&rsquo;, set this to &lsquo;<samp class="samp">true</samp>&rsquo; to
suppress the verbose countdown while waiting for a key to be pressed before
displaying the menu.
</p>
<p>This option is unset by default, and is deprecated in favour of the less
confusing &lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE=countdown</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">GRUB_HIDDEN_TIMEOUT_BUTTON</samp>&rsquo;</dt>
<dd><p>Variant of &lsquo;<samp class="samp">GRUB_HIDDEN_TIMEOUT</samp>&rsquo;, used to support vendor-specific power
buttons.  See <a class="xref" href="#Vendor-power_002don-keys">Using GRUB with vendor power-on keys</a>.
</p>
<p>This option is unset by default, and is deprecated in favour of the less
confusing &lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE=countdown</samp>&rsquo; or
&lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE=hidden</samp>&rsquo;.
</p>
</dd>
</dl>

<p>For more detailed customisation of <code class="command">grub2-mkconfig</code>&rsquo;s output, you may
edit the scripts in <samp class="file">/etc/grub.d</samp> directly.
<samp class="file">/etc/grub.d/40_custom</samp> is particularly useful for adding entire custom
menu entries; simply type the menu entries you want to add at the end of
that file, making sure to leave at least the first two lines intact.
</p>
<hr>
</div>
<div class="section-level-extent" id="Root-Identifcation-Heuristics">
<div class="nav-panel">
<p>
Next: <a href="#Shell_002dlike-scripting" accesskey="n" rel="next">Writing full configuration files directly</a>, Previous: <a href="#Simple-configuration" accesskey="p" rel="prev">Simple configuration handling</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Writing your own configuration file</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Root-Identifcation-Heuristics-1"><span>6.2 Root Identifcation Heuristics<a class="copiable-link" href="#Root-Identifcation-Heuristics-1"> &para;</a></span></h3>
<p>If the target operating system uses the Linux kernel, <code class="command">grub2-mkconfig</code>
attempts to identify the root file system via a heuristic algoirthm.  This
algorithm selects the identification method of the root file system by
considering three factors.  The first is if an initrd for the target operating
system is also present.  The second is &lsquo;<samp class="samp">GRUB_DISABLE_LINUX_UUID</samp>&rsquo; and if set
to &lsquo;<samp class="samp">true</samp>&rsquo;, prevents <code class="command">grub2-mkconfig</code> from identifying the root file
system by its UUID.  The third is &lsquo;<samp class="samp">GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; and if set
to &lsquo;<samp class="samp">true</samp>&rsquo;, prevents <code class="command">grub2-mkconfig</code> from identifying the root file
system via the UUID of its enclosing partition.  If the variables are assigned
any other value, that value is considered equivalent to &lsquo;<samp class="samp">false</samp>&rsquo;.  The
variables are also considered to be set to &lsquo;<samp class="samp">false</samp>&rsquo; if they are not set.
</p>
<p>When booting, the Linux kernel will delegate the task of mounting the root
filesystem to the initrd.  Most initrd images determine the root file system by
checking the Linux kernel&rsquo;s command-line for the &lsquo;<samp class="samp">root</samp>&rsquo; key and use its
value as the identification method of the root file system.  To improve the
reliability of booting, most initrd images also allow the root file system to be
identified by its UUID.  Because of this behavior, the <code class="command">grub2-mkconfig</code>
command will set &lsquo;<samp class="samp">root</samp>&rsquo; to &lsquo;<samp class="samp">root=UUID=...</samp>&rsquo; to provide the initrd with
the filesystem UUID of the root file system.
</p>
<p>If no initrd is detected or &lsquo;<samp class="samp">GRUB_DISABLE_LINUX_UUID</samp>&rsquo; is set to &lsquo;<samp class="samp">true</samp>&rsquo;
then <code class="command">grub2-command</code> will identify the root filesystem by setting the
kernel command-line variable &lsquo;<samp class="samp">root</samp>&rsquo; to &lsquo;<samp class="samp">root=PARTUUID=...</samp>&rsquo; unless
&lsquo;<samp class="samp">GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; is also set to &lsquo;<samp class="samp">true</samp>&rsquo;.  If
&lsquo;<samp class="samp">GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; is also set to &lsquo;<samp class="samp">true</samp>&rsquo;,
<code class="command">grub2-command</code> will identify by its Linux device name.
</p>
<p>The following table summarizes the behavior of the <code class="command">grub2-mkconfig</code>
command.
</p>
<table class="multitable">
<thead><tr><th>Initrd detected</th><th>GRUB_DISABLE_LINUX_PARTUUID Set To</th><th>GRUB_DISABLE_LINUX_UUID Set To</th><th>Linux Root ID Method</th></tr></thead>
<tbody><tr><td>false</td><td>false</td><td>false</td><td>part UUID</td></tr>
<tr><td>false</td><td>false</td><td>true</td><td>part UUID</td></tr>
<tr><td>false</td><td>true</td><td>false</td><td>dev name</td></tr>
<tr><td>false</td><td>true</td><td>true</td><td>dev name</td></tr>
<tr><td>true</td><td>false</td><td>false</td><td>fs UUID</td></tr>
<tr><td>true</td><td>false</td><td>true</td><td>part UUID</td></tr>
<tr><td>true</td><td>true</td><td>false</td><td>fs UUID</td></tr>
<tr><td>true</td><td>true</td><td>true</td><td>dev name</td></tr>
</tbody>
</table>

<p>Remember, &lsquo;<samp class="samp">GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; and &lsquo;<samp class="samp">GRUB_DISABLE_LINUX_UUID</samp>&rsquo;
are also considered to be set to &lsquo;<samp class="samp">true</samp>&rsquo; and &lsquo;<samp class="samp">false</samp>&rsquo;, respectively,
when they are unset.
</p>
<hr>
</div>
<div class="section-level-extent" id="Shell_002dlike-scripting">
<div class="nav-panel">
<p>
Next: <a href="#Multi_002dboot-manual-config" accesskey="n" rel="next">Multi-boot manual config</a>, Previous: <a href="#Root-Identifcation-Heuristics" accesskey="p" rel="prev">Root Identifcation Heuristics</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Writing your own configuration file</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Writing-full-configuration-files-directly"><span>6.3 Writing full configuration files directly<a class="copiable-link" href="#Writing-full-configuration-files-directly"> &para;</a></span></h3>

<p><samp class="file">grub.cfg</samp> is written in GRUB&rsquo;s built-in scripting language, which has
a syntax quite similar to that of GNU Bash and other Bourne shell
derivatives.
</p>
<h3 class="heading" id="Words"><span>Words<a class="copiable-link" href="#Words"> &para;</a></span></h3>

<p>A <em class="dfn">word</em> is a sequence of characters considered as a single unit by
GRUB.  Words are separated by <em class="dfn">metacharacters</em>, which are the following
plus space, tab, and newline:
</p>
<div class="example">
<pre class="example-preformatted">{ } | &amp; $ ; &lt; &gt;
</pre></div>
 
<p>Quoting may be used to include metacharacters in words; see below.
</p>
<h3 class="heading" id="Reserved-words"><span>Reserved words<a class="copiable-link" href="#Reserved-words"> &para;</a></span></h3>

<p>Reserved words have a special meaning to GRUB.  The following words are
recognised as reserved when unquoted and either the first word of a simple
command or the third word of a <code class="code">for</code> command:
</p>
<div class="example">
<pre class="example-preformatted">! [[ ]] { }
case do done elif else esac fi for function
if in menuentry select then time until while
</pre></div>

<p>Not all of these reserved words have a useful purpose yet; some are reserved
for future expansion.
</p>
<h3 class="heading" id="Quoting"><span>Quoting<a class="copiable-link" href="#Quoting"> &para;</a></span></h3>

<p>Quoting is used to remove the special meaning of certain characters or
words.  It can be used to treat metacharacters as part of a word, to prevent
reserved words from being recognised as such, and to prevent variable
expansion.
</p>
<p>There are three quoting mechanisms: the escape character, single quotes, and
double quotes.
</p>
<p>A non-quoted backslash (\) is the <em class="dfn">escape character</em>.  It preserves the
literal value of the next character that follows, with the exception of
newline.
</p>
<p>Enclosing characters in single quotes preserves the literal value of each
character within the quotes.  A single quote may not occur between single
quotes, even when preceded by a backslash.
</p>
<p>Enclosing characters in double quotes preserves the literal value of all
characters within the quotes, with the exception of &lsquo;<samp class="samp">$</samp>&rsquo; and &lsquo;<samp class="samp">\</samp>&rsquo;.
The &lsquo;<samp class="samp">$</samp>&rsquo; character retains its special meaning within double quotes.
The backslash retains its special meaning only when followed by one of the
following characters: &lsquo;<samp class="samp">$</samp>&rsquo;, &lsquo;<samp class="samp">&quot;</samp>&rsquo;, &lsquo;<samp class="samp">\</samp>&rsquo;, or newline.  A
backslash-newline pair is treated as a line continuation (that is, it is
removed from the input stream and effectively ignored<a class="footnote" id="DOCF7" href="#FOOT7"><sup>7</sup></a>).  A double quote may be quoted within
double quotes by preceding it with a backslash.
</p>
<h3 class="heading" id="Variable-expansion"><span>Variable expansion<a class="copiable-link" href="#Variable-expansion"> &para;</a></span></h3>

<p>The &lsquo;<samp class="samp">$</samp>&rsquo; character introduces variable expansion.  The variable name to
be expanded may be enclosed in braces, which are optional but serve to
protect the variable to be expanded from characters immediately following it
which could be interpreted as part of the name.
</p>
<p>Normal variable names begin with an alphabetic character, followed by zero
or more alphanumeric characters.  These names refer to entries in the GRUB
environment (see <a class="pxref" href="#Environment">GRUB environment variables</a>).
</p>
<p>Positional variable names consist of one or more digits.  They represent
parameters passed to function calls, with &lsquo;<samp class="samp">$1</samp>&rsquo; representing the first
parameter, and so on.
</p>
<p>The special variable name &lsquo;<samp class="samp">?</samp>&rsquo; expands to the exit status of the most
recently executed command.  When positional variable names are active, other
special variable names &lsquo;<samp class="samp">@</samp>&rsquo;, &lsquo;<samp class="samp">*</samp>&rsquo; and &lsquo;<samp class="samp">#</samp>&rsquo; are defined and they
expand to all positional parameters with necessary quoting, positional
parameters without any quoting, and positional parameter count respectively.
</p>
<h3 class="heading" id="Comments"><span>Comments<a class="copiable-link" href="#Comments"> &para;</a></span></h3>

<p>A word beginning with &lsquo;<samp class="samp">#</samp>&rsquo; causes that word and all remaining characters
on that line to be ignored.
</p>
<h3 class="heading" id="Simple-commands"><span>Simple commands<a class="copiable-link" href="#Simple-commands"> &para;</a></span></h3>

<p>A <em class="dfn">simple command</em> is a sequence of words separated by spaces or tabs
and terminated by a semicolon or a newline.  The first word specifies the
command to be executed.  The remaining words are passed as arguments to the
invoked command.
</p>
<p>The return value of a simple command is its exit status.  If the reserved
word <code class="code">!</code> precedes the command, then the return value is instead the
logical negation of the command&rsquo;s exit status.
</p>
<h3 class="heading" id="Compound-commands"><span>Compound commands<a class="copiable-link" href="#Compound-commands"> &para;</a></span></h3>

<p>A <em class="dfn">compound command</em> is one of the following:
</p>
<dl class="table">
<dt>for <var class="var">name</var> in <var class="var">word</var> &hellip;; do <var class="var">list</var>; done</dt>
<dd><p>The list of words following <code class="code">in</code> is expanded, generating a list of
items.  The variable <var class="var">name</var> is set to each element of this list in turn,
and <var class="var">list</var> is executed each time.  The return value is the exit status
of the last command that executes.  If the expansion of the items following
<code class="code">in</code> results in an empty list, no commands are executed, and the return
status is 0.
</p>
</dd>
<dt>if <var class="var">list</var>; then <var class="var">list</var>; [elif <var class="var">list</var>; then <var class="var">list</var>;] &hellip; [else <var class="var">list</var>;] fi</dt>
<dd><p>The <code class="code">if</code> <var class="var">list</var> is executed, where <var class="var">list</var> is a series of
<em class="dfn">simple command</em>s separated by a &quot;;&quot;.  If its exit status of the last
command is zero, the <code class="code">then</code> <var class="var">list</var> is executed.  Otherwise, each
<code class="code">elif</code> <var class="var">list</var> is executed in turn, and if its last command&rsquo;s exit
status is zero, the corresponding <code class="code">then</code> <var class="var">list</var> is executed and the
command completes. Otherwise, the <code class="code">else</code> <var class="var">list</var> is executed, if
present.  The exit status is the exit status of the last command executed, or
zero if no condition tested true.
</p>
</dd>
<dt>while <var class="var">cond</var>; do <var class="var">list</var>; done</dt>
<dt>until <var class="var">cond</var>; do <var class="var">list</var>; done</dt>
<dd><p>The <code class="code">while</code> command continuously executes the <code class="code">do</code> <var class="var">list</var> as
long as the last command in <var class="var">cond</var> returns an exit status of zero, where
<var class="var">cond</var> is a list of <em class="dfn">simple command</em>s separated by a &quot;;&quot;.  The
<code class="code">until</code> command is identical to the <code class="code">while</code> command, except that
the test is negated; the <code class="code">do</code> <var class="var">list</var> is executed as long as the
last command in <var class="var">cond</var> returns a non-zero exit status.  The exit status
of the <code class="code">while</code> and <code class="code">until</code> commands is the exit status of the last
<code class="code">do</code> <var class="var">list</var> command executed, or zero if none was executed.
</p>
</dd>
<dt>function <var class="var">name</var> { <var class="var">command</var>; &hellip; }</dt>
<dd><p>This defines a function named <var class="var">name</var>.  The <em class="dfn">body</em> of the function is
the list of commands within braces, each of which must be terminated with a
semicolon or a newline.  This list of commands will be executed whenever
<var class="var">name</var> is specified as the name of a simple command.  Function
definitions do not affect the exit status in <code class="code">$?</code>.  When executed, the
exit status of a function is the exit status of the last command executed in
the body.
</p>
</dd>
<dt>menuentry <var class="var">title</var> [<samp class="option">--class=class</samp> &hellip;] [<samp class="option">--users=users</samp>] [<samp class="option">--unrestricted</samp>] [<samp class="option">--hotkey=key</samp>] [<samp class="option">--id=id</samp>] { <var class="var">command</var>; &hellip; }</dt>
<dd><p>See <a class="xref" href="#menuentry">menuentry</a>.
</p></dd>
</dl>

<h3 class="heading" id="Built_002din-Commands"><span>Built-in Commands<a class="copiable-link" href="#Built_002din-Commands"> &para;</a></span></h3>

<p>Some built-in commands are also provided by GRUB script to help script
writers perform actions that are otherwise not possible.  For example, these
include commands to jump out of a loop without fully completing it, etc.
</p>
<dl class="table">
<dt>break [<code class="code">n</code>]</dt>
<dd><p>Exit from within a <code class="code">for</code>, <code class="code">while</code>, or <code class="code">until</code> loop.  If
<code class="code">n</code> is specified, break <code class="code">n</code> levels.  <code class="code">n</code> must be greater than
or equal to 1.  If <code class="code">n</code> is greater than the number of enclosing loops,
all enclosing loops are exited.  The return value is 0 unless <code class="code">n</code> is
not greater than or equal to 1.
</p>
</dd>
<dt>continue [<code class="code">n</code>]</dt>
<dd><p>Resume the next iteration of the enclosing <code class="code">for</code>, <code class="code">while</code> or
<code class="code">until</code> loop.  If <code class="code">n</code> is specified, resume at the <code class="code">n</code>th
enclosing loop.  <code class="code">n</code> must be greater than or equal to 1.  If <code class="code">n</code>
is greater than the number of enclosing loops, the last enclosing loop (the
<em class="dfn">top-level</em> loop) is resumed.  The return value is 0 unless <code class="code">n</code> is
not greater than or equal to 1.
</p>
</dd>
<dt>return [<code class="code">n</code>]</dt>
<dd><p>Causes a function to exit with the return value specified by <code class="code">n</code>.  If
<code class="code">n</code> is omitted, the return status is that of the last command executed
in the function body.  If used outside a function the return status is
false.
</p>
</dd>
<dt>setparams [<code class="code">arg</code>] &hellip;</dt>
<dd><p>Replace positional parameters starting with <code class="code">$1</code> with arguments to
<code class="command">setparams</code>.
</p>
</dd>
<dt>shift [<code class="code">n</code>]</dt>
<dd><p>The positional parameters from <code class="code">n</code>+1 &hellip; are renamed to
<code class="code">$1</code>&hellip;.  Parameters represented by the numbers <code class="code">$#</code> down to
<code class="code">$#</code>-<code class="code">n</code>+1 are unset.  <code class="code">n</code> must be a non-negative number less
than or equal to <code class="code">$#</code>.  If <code class="code">n</code> is 0, no parameters are changed.
If <code class="code">n</code> is not given, it is assumed to be 1.  If <code class="code">n</code> is greater
than <code class="code">$#</code>, the positional parameters are not changed.  The return
status is greater than zero if <code class="code">n</code> is greater than <code class="code">$#</code> or less
than zero; otherwise 0.
</p>
</dd>
</dl>

<hr>
</div>
<div class="section-level-extent" id="Multi_002dboot-manual-config">
<div class="nav-panel">
<p>
Next: <a href="#Embedded-configuration" accesskey="n" rel="next">Embedding a configuration file into GRUB</a>, Previous: <a href="#Shell_002dlike-scripting" accesskey="p" rel="prev">Writing full configuration files directly</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Writing your own configuration file</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Multi_002dboot-manual-config-1"><span>6.4 Multi-boot manual config<a class="copiable-link" href="#Multi_002dboot-manual-config-1"> &para;</a></span></h3>

<p>Currently autogenerating config files for multi-boot environments depends on
os-prober and has several shortcomings. While fixing it is scheduled for the
next release, meanwhile you can make use of the power of GRUB syntax and do it
yourself. A possible configuration is detailed here, feel free to adjust to your
needs.
</p>
<p>First create a separate GRUB partition, big enough to hold GRUB. Some of the
following entries show how to load OS installer images from this same partition,
for that you obviously need to make the partition large enough to hold those
images as well.
Mount this partition on/mnt/boot and disable GRUB in all OSes and manually
install self-compiled latest GRUB with:
</p>
<p><code class="code">grub2-install --boot-directory=/mnt/boot /dev/sda</code>
</p>
<p>In all the OSes install GRUB tools but disable installing GRUB in bootsector,
so you&rsquo;ll have menu.lst and grub.cfg available for use. Also disable os-prober
use by setting:
</p>
<p><code class="code">GRUB_DISABLE_OS_PROBER=true</code>
</p>
<p>in /etc/default/grub
</p>
<p>Then write a grub.cfg (/mnt/boot/grub2/grub.cfg):
</p>
<div class="example">
<pre class="example-preformatted">

menuentry &quot;OS using grub2&quot; {
   insmod xfs
   search --set=root --label OS1 --hint hd0,msdos8
   configfile /boot/grub2/grub.cfg
}

menuentry &quot;OS using grub2-legacy&quot; {
   insmod ext2
   search --set=root --label OS2 --hint hd0,msdos6
   legacy_configfile /boot/grub2/menu.lst
}

menuentry &quot;Windows XP&quot; {
   insmod ntfs
   search --set=root --label WINDOWS_XP --hint hd0,msdos1
   ntldr /ntldr
}

menuentry &quot;Windows 7&quot; {
   insmod ntfs
   search --set=root --label WINDOWS_7 --hint hd0,msdos2
   ntldr /bootmgr
}

menuentry &quot;FreeBSD&quot; {
          insmod zfs
          search --set=root --label freepool --hint hd0,msdos7
          kfreebsd /freebsd@/boot/kernel/kernel
          kfreebsd_module_elf /freebsd@/boot/kernel/opensolaris.ko
          kfreebsd_module_elf /freebsd@/boot/kernel/zfs.ko
          kfreebsd_module /freebsd@/boot/zfs/zpool.cache type=/boot/zfs/zpool.cache
          set kFreeBSD.vfs.root.mountfrom=zfs:freepool/freebsd
          set kFreeBSD.hw.psm.synaptics_support=1
}

menuentry &quot;experimental GRUB&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          multiboot /experimental/grub/i386-pc/core.img
}

menuentry &quot;Fedora 16 installer&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          linux /fedora/vmlinuz lang=en_US keymap=sg resolution=1280x800
          initrd /fedora/initrd.img
}

menuentry &quot;Fedora rawhide installer&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          linux /fedora/vmlinuz repo=ftp://mirror.switch.ch/mirror/fedora/linux/development/rawhide/x86_64 lang=en_US keymap=sg resolution=1280x800
          initrd /fedora/initrd.img
}

menuentry &quot;Debian sid installer&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          linux /debian/dists/sid/main/installer-amd64/current/images/hd-media/vmlinuz
          initrd /debian/dists/sid/main/installer-amd64/current/images/hd-media/initrd.gz
}

</pre></div>

<p>Notes:
</p><ul class="itemize mark-bullet">
<li>Argument to search after &ndash;label is FS LABEL. You can also use UUIDs with &ndash;fs-uuid UUID instead of &ndash;label LABEL. You could also use direct <code class="code">root=hd0,msdosX</code> but this is not recommended due to device name instability.
</li></ul>

<hr>
</div>
<div class="section-level-extent" id="Embedded-configuration">
<div class="nav-panel">
<p>
Previous: <a href="#Multi_002dboot-manual-config" accesskey="p" rel="prev">Multi-boot manual config</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Writing your own configuration file</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Embedding-a-configuration-file-into-GRUB"><span>6.5 Embedding a configuration file into GRUB<a class="copiable-link" href="#Embedding-a-configuration-file-into-GRUB"> &para;</a></span></h3>

<p>GRUB supports embedding a configuration file directly into the core image,
so that it is loaded before entering normal mode.  This is useful, for
example, when it is not straightforward to find the real configuration file,
or when you need to debug problems with loading that file.
<code class="command">grub2-install</code> uses this feature when it is not using BIOS disk
functions or when installing to a different disk from the one containing
<samp class="file">/boot/grub</samp>, in which case it needs to use the <code class="command">search</code>
command (see <a class="pxref" href="#search">search</a>) to find <samp class="file">/boot/grub</samp>.
</p>
<p>To embed a configuration file, use the <samp class="option">-c</samp> option to
<code class="command">grub2-mkimage</code>.  The file is copied into the core image, so it may
reside anywhere on the file system, and may be removed after running
<code class="command">grub2-mkimage</code>.
</p>
<p>After the embedded configuration file (if any) is executed, GRUB will load
the &lsquo;<samp class="samp">normal</samp>&rsquo; module (see <a class="pxref" href="#normal">normal</a>), which will then read the real
configuration file from <samp class="file">$prefix/grub.cfg</samp>.  By this point, the
<code class="code">root</code> variable will also have been set to the root device name.  For
example, <code class="code">prefix</code> might be set to &lsquo;<samp class="samp">(hd0,1)/boot/grub</samp>&rsquo;, and
<code class="code">root</code> might be set to &lsquo;<samp class="samp">hd0,1</samp>&rsquo;.  Thus, in most cases, the embedded
configuration file only needs to set the <code class="code">prefix</code> and <code class="code">root</code>
variables, and then drop through to GRUB&rsquo;s normal processing.  A typical
example of this might look like this:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">search.fs_uuid 01234567-89ab-cdef-0123-456789abcdef root
set prefix=($root)/boot/grub
</pre></div></div>

<p>(The &lsquo;<samp class="samp">search_fs_uuid</samp>&rsquo; module must be included in the core image for this
example to work.)
</p>
<p>In more complex cases, it may be useful to read other configuration files
directly from the embedded configuration file.  This allows such things as
reading files not called <samp class="file">grub.cfg</samp>, or reading files from a directory
other than that where GRUB&rsquo;s loadable modules are installed.  To do this,
include the &lsquo;<samp class="samp">configfile</samp>&rsquo; and &lsquo;<samp class="samp">normal</samp>&rsquo; modules in the core image,
and embed a configuration file that uses the <code class="command">configfile</code> command to
load another file.  The following example of this also requires the
<code class="command">echo</code>, <code class="command">search_label</code>, and <code class="command">test</code> modules to be
included in the core image:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">search.fs_label grub root
if [ -e /boot/grub2/example/test1.cfg ]; then
    set prefix=($root)/boot/grub
    configfile /boot/grub2/example/test1.cfg
else
    if [ -e /boot/grub2/example/test2.cfg ]; then
        set prefix=($root)/boot/grub
        configfile /boot/grub2/example/test2.cfg
    else
        echo &quot;Could not find an example configuration file!&quot;
    fi
fi
</pre></div></div>

<p>The embedded configuration file may not contain menu entries directly, but
may only read them from elsewhere using <code class="command">configfile</code>.
</p>
<hr>
</div>
</div>
<div class="chapter-level-extent" id="Theme-file-format">
<div class="nav-panel">
<p>
Next: <a href="#Network" accesskey="n" rel="next">Booting GRUB from the network</a>, Previous: <a href="#Configuration" accesskey="p" rel="prev">Writing your own configuration file</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Theme-file-format-1"><span>7 Theme file format<a class="copiable-link" href="#Theme-file-format-1"> &para;</a></span></h2>
<ul class="mini-toc">
<li><a href="#Introduction-1" accesskey="1">Introduction</a></li>
<li><a href="#Theme-Elements" accesskey="2">Theme Elements</a></li>
<li><a href="#Theme-File-Manual" accesskey="3">Theme File Manual</a></li>
</ul>
<div class="section-level-extent" id="Introduction-1">
<h3 class="section"><span>7.1 Introduction<a class="copiable-link" href="#Introduction-1"> &para;</a></span></h3>
<p>The GRUB graphical menu supports themes that can customize the layout and
appearance of the GRUB boot menu.  The theme is configured through a plain
text file that specifies the layout of the various GUI components (including
the boot menu, timeout progress bar, and text messages) as well as the
appearance using colors, fonts, and images. Example is available in docs/example_theme.txt
</p>
</div>
<div class="section-level-extent" id="Theme-Elements">
<h3 class="section"><span>7.2 Theme Elements<a class="copiable-link" href="#Theme-Elements"> &para;</a></span></h3>
<ul class="mini-toc">
<li><a href="#Colors" accesskey="1">Colors</a></li>
<li><a href="#Fonts" accesskey="2">Fonts</a></li>
<li><a href="#Progress-Bar" accesskey="3">Progress Bar</a></li>
<li><a href="#Circular-Progress-Indicator" accesskey="4">Circular Progress Indicator</a></li>
<li><a href="#Labels" accesskey="5">Labels</a></li>
<li><a href="#Boot-Menu" accesskey="6">Boot Menu</a></li>
<li><a href="#Styled-Boxes" accesskey="7">Styled Boxes</a></li>
<li><a href="#Creating-Styled-Box-Images" accesskey="8">Creating Styled Box Images</a></li>
</ul>
<div class="subsection-level-extent" id="Colors">
<h4 class="subsection"><span>7.2.1 Colors<a class="copiable-link" href="#Colors"> &para;</a></span></h4>

<p>Colors can be specified in several ways:
</p>
<ul class="itemize mark-bullet">
<li>HTML-style &ldquo;#RRGGBB&rdquo; or &ldquo;#RGB&rdquo; format, where *R*, *G*, and *B* are hexadecimal digits (e.g., &ldquo;#8899FF&rdquo;)
</li><li>as comma-separated decimal RGB values (e.g., &ldquo;128, 128, 255&rdquo;)
</li><li>with &ldquo;SVG 1.0 color names&rdquo; (e.g., &ldquo;cornflowerblue&rdquo;) which must be specified in lowercase.
</li></ul>
</div>
<div class="subsection-level-extent" id="Fonts">
<h4 class="subsection"><span>7.2.2 Fonts<a class="copiable-link" href="#Fonts"> &para;</a></span></h4>
<p>The fonts GRUB uses &ldquo;PFF2 font format&rdquo; bitmap fonts.  Fonts are specified
with full font names.  Currently there is no
provision for a preference list of fonts, or deriving one font from another.
Fonts are loaded with the &ldquo;loadfont&rdquo; command in GRUB (<a class="ref" href="#loadfont">loadfont</a>).  To see the list of
loaded fonts, execute the &ldquo;lsfonts&rdquo; command (<a class="ref" href="#lsfonts">lsfonts</a>).  If there are too many fonts to
fit on screen, do &ldquo;set pager=1&rdquo; before executing &ldquo;lsfonts&rdquo;.
</p>

</div>
<div class="subsection-level-extent" id="Progress-Bar">
<h4 class="subsection"><span>7.2.3 Progress Bar<a class="copiable-link" href="#Progress-Bar"> &para;</a></span></h4>

<div class="float" id="Pixmap_002dstyled-progress-bar">
<div class="type-number-float"><p><strong class="strong">Figure 7.1</strong></p></div></div>
<div class="float" id="Plain-progress-bar_002c-drawn-with-solid-color_002e">
<div class="type-number-float"><p><strong class="strong">Figure 7.2</strong></p></div></div>
<p>Progress bars are used to display the remaining time before GRUB boots the
default menu entry.  To create a progress bar that will display the remaining
time before automatic boot, simply create a &ldquo;progress_bar&rdquo; component with
the id &ldquo;__timeout__&rdquo;.  This indicates to GRUB that the progress bar should
be updated as time passes, and it should be made invisible if the countdown to
automatic boot is interrupted by the user.
</p>
<p>Progress bars may optionally have text displayed on them.  This text is
controlled by variable &ldquo;text&rdquo; which contains a printf template with the
only argument %d is the number of seconds remaining. Additionally special
values &ldquo;@TIMEOUT_NOTIFICATION_SHORT@&rdquo;, &ldquo;@TIMEOUT_NOTIFICATION_MIDDLE@&rdquo;,
&ldquo;@TIMEOUT_NOTIFICATION_LONG@&rdquo; are replaced with standard and translated
templates.
</p>
</div>
<div class="subsection-level-extent" id="Circular-Progress-Indicator">
<h4 class="subsection"><span>7.2.4 Circular Progress Indicator<a class="copiable-link" href="#Circular-Progress-Indicator"> &para;</a></span></h4>

<p>The circular progress indicator functions similarly to the progress bar.  When
given an id of &ldquo;__timeout__&rdquo;, GRUB updates the circular progress indicator&rsquo;s
value to indicate the time remaining.  For the circular progress indicator,
there are two images used to render it:  the *center* image, and the *tick*
image.  The center image is rendered in the center of the component, while the
tick image is used to render each mark along the circumference of the
indicator.
</p>

</div>
<div class="subsection-level-extent" id="Labels">
<h4 class="subsection"><span>7.2.5 Labels<a class="copiable-link" href="#Labels"> &para;</a></span></h4>

<p>Text labels can be placed on the boot screen.  The font, color, and horizontal
alignment can be specified for labels.  If a label is given the id
&ldquo;__timeout__&rdquo;, then the &ldquo;text&rdquo; property for that label is also updated
with a message informing the user of the number of seconds remaining until
automatic boot.  This is useful in case you want the text displayed somewhere
else instead of directly on the progress bar.
</p>

</div>
<div class="subsection-level-extent" id="Boot-Menu">
<h4 class="subsection"><span>7.2.6 Boot Menu<a class="copiable-link" href="#Boot-Menu"> &para;</a></span></h4>

<p>The boot menu where GRUB displays the menu entries from the &ldquo;grub.cfg&rdquo; file.
It is a list of items, where each item has a title and an optional icon.  The
icon is selected based on the *classes* specified for the menu entry.  If
there is a PNG file named &ldquo;myclass.png&rdquo; in the &ldquo;grub/themes/icons&rdquo;
directory, it will be displayed for items which have the class *myclass*.  The
boot menu can be customized in several ways, such as the font and color used
for the menu entry title, and by specifying styled boxes for the menu itself
and for the selected item highlight.
</p>

</div>
<div class="subsection-level-extent" id="Styled-Boxes">
<h4 class="subsection"><span>7.2.7 Styled Boxes<a class="copiable-link" href="#Styled-Boxes"> &para;</a></span></h4>

<p>One of the most important features for customizing the layout is the use of
 *styled boxes*.  A styled box is composed of 9 rectangular (and potentially
empty) regions, which are used to seamlessly draw the styled box on screen:
</p>
<table class="multitable">
<tbody><tr><td width="30%">Northwest (nw)</td><td width="30%">North (n)</td><td width="30%">Northeast (ne)</td></tr>
<tr><td width="30%">West (w)</td><td width="30%">Center (c)</td><td width="30%">East (e)</td></tr>
<tr><td width="30%">Southwest (sw)</td><td width="30%">South (s)</td><td width="30%">Southeast (se)</td></tr>
</tbody>
</table>

<p>To support any size of box on screen, the center slice and the slices for the
top, bottom, and sides are all scaled to the correct size for the component on
screen, using the following rules:
</p>
<ol class="enumerate">
<li> The edge slices (north, south, east, and west) are scaled in the direction of the edge they are adjacent to.  For instance, the west slice is scaled vertically.
</li><li> The corner slices (northwest, northeast, southeast, and southwest) are not scaled.
</li><li> The center slice is scaled to fill the remaining space in the middle.
</li></ol>

<p>As an example of how an image might be sliced up, consider the styled box
used for a terminal view.
</p>
<div class="float" id="An-example-of-the-slices-_0028in-red_0029-used-for-a-terminal-window_002e-This-drawing-was-created-and-sliced-in-Inkscape_005f_002c-as-the-next-section-explains_002e">
<div class="type-number-float"><p><strong class="strong">Figure 7.3</strong></p></div></div>   
</div>
<div class="subsection-level-extent" id="Creating-Styled-Box-Images">
<h4 class="subsection"><span>7.2.8 Creating Styled Box Images<a class="copiable-link" href="#Creating-Styled-Box-Images"> &para;</a></span></h4>

<p>The Inkscape_ scalable vector graphics editor is a very useful tool for
creating styled box images.  One process that works well for slicing a drawing
into the necessary image slices is:
</p>
<ol class="enumerate">
<li> Create or open the drawing you&rsquo;d like use.
</li><li> Create a new layer on the top of the layer stack.  Make it visible.  Select this layer as the current layer.
</li><li> Draw 9 rectangles on your drawing where you&rsquo;d like the slices to be.  Clear the fill option, and set the stroke to 1 pixel wide solid stroke.  The corners of the slices must meet precisely; if it is off by a single pixel, it will probably be evident when the styled box is rendered in the GRUB menu.  You should probably go to File | Document Properties | Grids and enable a grid or create a guide (click on one of the rulers next to the drawing and drag over the drawing; release the mouse button to place the guide) to help place the rectangles precisely.
</li><li> Right click on the center slice rectangle and choose Object Properties. Change the &quot;Id&quot; to &ldquo;slice_c&ldquo; and click Set.  Repeat this for the remaining 8 rectangles, giving them Id values of &ldquo;slice_n&ldquo;, &ldquo;slice_ne&ldquo;, &ldquo;slice_e&ldquo;, and so on according to the location.
</li><li> Save the drawing.
</li><li> Select all the slice rectangles.  With the slice layer selected, you can simply press Ctrl+A to select all rectangles.  The status bar should indicate that 9 rectangles are selected.
</li><li> Click the layer hide icon for the slice layer in the layer palette.  The rectangles will remain selected, even though they are hidden.
</li><li> Choose File | Export Bitmap and check the *Batch export 9 selected objects* box.  Make sure that *Hide all except selected* is unchecked. click *Export*.  This will create PNG files in the same directory as the drawing, named after the slices.  These can now be used for a styled box in a GRUB theme.
</li></ol>

</div>
</div>
<div class="section-level-extent" id="Theme-File-Manual">
<h3 class="section"><span>7.3 Theme File Manual<a class="copiable-link" href="#Theme-File-Manual"> &para;</a></span></h3>

<p>The theme file is a plain text file.  Lines that begin with &ldquo;#&ldquo; are ignored
and considered comments.  (Note: This may not be the case if the previous line
ended where a value was expected.)
</p>
<p>The theme file contains two types of statements:
</p><ol class="enumerate">
<li> Global properties.
</li><li> Component construction.
</li></ol>

<ul class="mini-toc">
<li><a href="#Global-Properties" accesskey="1">Global Properties</a></li>
<li><a href="#Format" accesskey="2">Format</a></li>
<li><a href="#Global-Property-List" accesskey="3">Global Property List</a></li>
<li><a href="#Component-Construction" accesskey="4">Component Construction</a></li>
<li><a href="#Component-List" accesskey="5">Component List</a></li>
<li><a href="#Common-properties" accesskey="6">Common properties</a></li>
</ul>
<div class="subsection-level-extent" id="Global-Properties">
<h4 class="subsection"><span>7.3.1 Global Properties<a class="copiable-link" href="#Global-Properties"> &para;</a></span></h4>

</div>
<div class="subsection-level-extent" id="Format">
<h4 class="subsection"><span>7.3.2 Format<a class="copiable-link" href="#Format"> &para;</a></span></h4>

<p>Global properties are specified with the simple format:
</p><ul class="itemize mark-bullet">
<li>name1: value1
</li><li>name2: &quot;value which may contain spaces&quot;
</li><li>name3: #88F
</li></ul>

<p>In this example, name3 is assigned a color value.
</p>

</div>
<div class="subsection-level-extent" id="Global-Property-List">
<h4 class="subsection"><span>7.3.3 Global Property List<a class="copiable-link" href="#Global-Property-List"> &para;</a></span></h4>

<table class="multitable">
<tbody><tr><td width="30%">title-text</td><td width="60%">Specifies the text to display at the top center of the screen as a title.</td></tr>
<tr><td width="30%">title-font</td><td width="60%">Defines the font used for the title message at the top of the screen.</td></tr>
<tr><td width="30%">title-color</td><td width="60%">Defines the color of the title message.</td></tr>
<tr><td width="30%">message-font</td><td width="60%">Currently unused. Left for backward compatibility.</td></tr>
<tr><td width="30%">message-color</td><td width="60%">Currently unused. Left for backward compatibility.</td></tr>
<tr><td width="30%">message-bg-color</td><td width="60%">Currently unused. Left for backward compatibility.</td></tr>
<tr><td width="30%">desktop-image</td><td width="60%">Specifies the image to use as the background.  It will be scaled
   to fit the screen size or proportionally scaled depending on the scale
   method.</td></tr>
<tr><td width="30%">desktop-image-scale-method</td><td width="60%">Specifies the scaling method for the *desktop-image*. Options are
   &ldquo;stretch&ldquo;, &ldquo;crop&ldquo;, &ldquo;padding&ldquo;, &ldquo;fitwidth&ldquo;, &ldquo;fitheight&ldquo;.
   &ldquo;stretch&ldquo; for fitting the screen size. Otherwise it is proportional
   scaling of a part of *desktop-image* to the part of the screen.
   &ldquo;crop&ldquo; part of the *desktop-image* will be proportionally scaled to
   fit the screen sizes. &ldquo;padding&ldquo; the entire *desktop-image* will be
   contained on the screen. &ldquo;fitwidth&ldquo; for fitting the *desktop-image*&rsquo;s
   width with screen width. &ldquo;fitheight&ldquo; for fitting the *desktop-image*&rsquo;s
   height with the screen height. Default is &ldquo;stretch&ldquo;.</td></tr>
<tr><td width="30%">desktop-image-h-align</td><td width="60%">Specifies the horizontal alignment of the *desktop-image* if
   *desktop-image-scale-method* isn&rsquo;t equeal to &ldquo;stretch&ldquo;. Options are
   &ldquo;left&ldquo;, &ldquo;center&ldquo;, &ldquo;right&ldquo;. Default is &ldquo;center&ldquo;.</td></tr>
<tr><td width="30%">desktop-image-v-align</td><td width="60%">Specifies the vertical alignment of the *desktop-image* if
   *desktop-image-scale-method* isn&rsquo;t equeal to &ldquo;stretch&ldquo;. Options are
   &ldquo;top&ldquo;, &ldquo;center&ldquo;, &ldquo;bottom&ldquo;. Default is &ldquo;center&ldquo;.</td></tr>
<tr><td width="30%">desktop-color</td><td width="60%">Specifies the color for the background if *desktop-image* is not
   specified.</td></tr>
<tr><td width="30%">terminal-box</td><td width="60%">Specifies the file name pattern for the styled box slices used for the
   command line terminal window.  For example, &ldquo;terminal-box: terminal_*.png&ldquo;
   will use the images &ldquo;terminal_c.png&ldquo; as the center area, &ldquo;terminal_n.png&ldquo;
   as the north (top) edge, &ldquo;terminal_nw.png&ldquo; as the northwest (upper left)
   corner, and so on.  If the image for any slice is not found, it will simply
   be left empty.</td></tr>
<tr><td width="30%">terminal-border</td><td width="60%">Specifies the border width of the terminal window.</td></tr>
<tr><td width="30%">terminal-left</td><td width="60%">Specifies the left coordinate of the terminal window.</td></tr>
<tr><td width="30%">terminal-top</td><td width="60%">Specifies the top coordinate of the terminal window.</td></tr>
<tr><td width="30%">terminal-width</td><td width="60%">Specifies the width of the terminal window.</td></tr>
<tr><td width="30%">terminal-height</td><td width="60%">Specifies the height of the terminal window.</td></tr>
</tbody>
</table>

</div>
<div class="subsection-level-extent" id="Component-Construction">
<h4 class="subsection"><span>7.3.4 Component Construction<a class="copiable-link" href="#Component-Construction"> &para;</a></span></h4>

<p>Greater customizability comes is provided by components.  A tree of components
forms the user interface.  *Containers* are components that can contain other
components, and there is always a single root component which is an instance
of a *canvas* container.
</p>
<p>Components are created in the theme file by prefixing the type of component
with a &rsquo;+&rsquo; sign:
</p>
<p><code class="code">   + label { text=&quot;GRUB&quot; font=&quot;aqui 11&quot; color=&quot;#8FF&quot; } </code>
</p>
<p>properties of a component are specified as &quot;name = value&quot; (whitespace
surrounding tokens is optional and is ignored) where *value* may be:
</p><ul class="itemize mark-bullet">
<li>a single word (e.g., &ldquo;align = center&ldquo;, &ldquo;color = #FF8080&ldquo;),
</li><li>a quoted string (e.g., &ldquo;text = &quot;Hello, World!&quot;&ldquo;), or
</li><li>a tuple (e.g., &ldquo;preferred_size = (120, 80)&ldquo;).
</li></ul>

</div>
<div class="subsection-level-extent" id="Component-List">
<h4 class="subsection"><span>7.3.5 Component List<a class="copiable-link" href="#Component-List"> &para;</a></span></h4>

<p>The following is a list of the components and the properties they support.
</p>
<ul class="itemize mark-bullet">
<li>label
   A label displays a line of text.
   
<p>Properties:
   </p><table class="multitable">
<tbody><tr><td width="20%">id</td><td width="70%">Set to &ldquo;__timeout__&ldquo; to display the time elapsed to an automatical
      boot of the default entry.</td></tr>
<tr><td width="20%">text</td><td width="70%">The text to display. If &ldquo;id&ldquo; is set to &ldquo;__timeout__&ldquo; and no
      &ldquo;text&ldquo; property is set then the amount of seconds will be shown.
      If set to &ldquo;@KEYMAP_SHORT@&ldquo;, &ldquo;@KEYMAP_MIDDLE@&ldquo; or
      &ldquo;@KEYMAP_LONG@&ldquo; then predefined hotkey information will be shown.</td></tr>
<tr><td width="20%">font</td><td width="70%">The font to use for text display.</td></tr>
<tr><td width="20%">color</td><td width="70%">The color of the text.</td></tr>
<tr><td width="20%">align</td><td width="70%">The horizontal alignment of the text within the component.
      Options are &ldquo;left&ldquo;, &ldquo;center&ldquo; and &ldquo;right&ldquo;.</td></tr>
<tr><td width="20%">visible</td><td width="70%">Set to &ldquo;false&ldquo; to hide the label.</td></tr>
</tbody>
</table>

</li><li>image
   A component that displays an image.  The image is scaled to fit
   the component.

<p>Properties:
</p>
<table class="multitable">
<tbody><tr><td width="20%">file</td><td width="70%">The full path to the image file to load.</td></tr>
</tbody>
</table>

</li><li>progress_bar
   Displays a horizontally oriented progress bar.  It can be rendered using
   simple solid filled rectangles, or using a pair of pixmap styled boxes.

<p>Properties:
</p>
<table class="multitable">
<tbody><tr><td width="20%">id</td><td width="70%">Set to &ldquo;__timeout__&ldquo; to display the time elapsed to an automatical
      boot of the default entry.</td></tr>
<tr><td width="20%">fg_color</td><td width="70%">The foreground color for plain solid color rendering.</td></tr>
<tr><td width="20%">bg_color</td><td width="70%">The background color for plain solid color rendering.</td></tr>
<tr><td width="20%">border_color</td><td width="70%">The border color for plain solid color rendering.</td></tr>
<tr><td width="20%">text_color</td><td width="70%">The text color.</td></tr>
<tr><td width="20%">bar_style</td><td width="70%">The styled box specification for the frame of the progress bar.
      Example: &ldquo;progress_frame_*.png&ldquo;
      If the value is equal to &ldquo;highlight_style&ldquo; then no styled boxes
      will be shown.</td></tr>
<tr><td width="20%">highlight_style</td><td width="70%">The styled box specification for the highlighted region of the
      progress bar. This box will be used to paint just the highlighted region
      of the bar, and will be increased in size as the bar nears completion.
      Example: &ldquo;progress_hl_*.png&ldquo;.
      If the value is equal to &ldquo;bar_style&ldquo; then no styled boxes
      will be shown.</td></tr>
<tr><td width="20%">highlight_overlay</td><td width="70%">If this option is set to &ldquo;true&ldquo; then the highlight box
      side slices (every slice except the center slice) will overlay the
      frame box side slices. And the center slice of the highlight box
      can move all the way (from top to bottom), being drawn on the center
      slice of the frame box. That way we can make a progress bar with
      round-shaped edges so there won&rsquo;t be a free space from the highlight to
      the frame in top and bottom scrollbar positions. Default is &ldquo;false&ldquo;.</td></tr>
<tr><td width="20%">font</td><td width="70%">The font to use for progress bar.</td></tr>
<tr><td width="20%">text</td><td width="70%">The text to display on the progress bar.  If the progress bar&rsquo;s ID
      is set to &ldquo;__timeout__&ldquo; and the value of this property is set to
      &ldquo;@TIMEOUT_NOTIFICATION_SHORT@&ldquo;, &ldquo;@TIMEOUT_NOTIFICATION_MIDDLE@&ldquo;
      or &ldquo;@TIMEOUT_NOTIFICATION_LONG@&ldquo;, then GRUB will update this
      property with an informative message as the timeout approaches.</td></tr>
</tbody>
</table>

</li><li>circular_progress
   Displays a circular progress indicator.  The appearance of this component
   is determined by two images:  the *center* image and the *tick* image.  The
   center image is generally larger and will be drawn in the center of the
   component.  Around the circumference of a circle within the component, the
   tick image will be drawn a certain number of times, depending on the
   properties of the component.

<p>Properties:
</p>
<table class="multitable">
<tbody><tr><td width="30%">id</td><td width="60%">Set to &ldquo;__timeout__&ldquo; to display the time elapsed to an automatical
      boot of the default entry.</td></tr>
<tr><td width="30%">center_bitmap</td><td width="60%">The file name of the image to draw in the center of the component.</td></tr>
<tr><td width="30%">tick_bitmap</td><td width="60%">The file name of the image to draw for the tick marks.</td></tr>
<tr><td width="30%">num_ticks</td><td width="60%">The number of ticks that make up a full circle.</td></tr>
<tr><td width="30%">ticks_disappear</td><td width="60%">Boolean value indicating whether tick marks should progressively appear,
      or progressively disappear as *value* approaches *end*.  Specify
      &ldquo;true&ldquo; or &ldquo;false&ldquo;. Default is &ldquo;false&ldquo;.</td></tr>
<tr><td width="30%">start_angle</td><td width="60%">The position of the first tick mark to appear or disappear.
      Measured in &quot;parrots&quot;, 1 &quot;parrot&quot; = 1 / 256 of the full circle.
      Use values &ldquo;xxx deg&ldquo; or &ldquo;xxx \xc2\xb0&ldquo; to set the angle in degrees.</td></tr>
</tbody>
</table>

</li><li>boot_menu
   Displays the GRUB boot menu.  It allows selecting items and executing them.

<p>Properties:
</p>
<table class="multitable">
<tbody><tr><td width="40%">item_font</td><td width="50%">The font to use for the menu item titles.</td></tr>
<tr><td width="40%">selected_item_font</td><td width="50%">The font to use for the selected menu item, or &ldquo;inherit&ldquo; (the default)
      to use &ldquo;item_font&ldquo; for the selected menu item as well.</td></tr>
<tr><td width="40%">item_color</td><td width="50%">The color to use for the menu item titles.</td></tr>
<tr><td width="40%">selected_item_color</td><td width="50%">The color to use for the selected menu item, or &ldquo;inherit&ldquo; (the default)
      to use &ldquo;item_color&ldquo; for the selected menu item as well.</td></tr>
<tr><td width="40%">icon_width</td><td width="50%">The width of menu item icons.  Icons are scaled to the specified size.</td></tr>
<tr><td width="40%">icon_height</td><td width="50%">The height of menu item icons.</td></tr>
<tr><td width="40%">item_height</td><td width="50%">The height of each menu item in pixels.</td></tr>
<tr><td width="40%">item_padding</td><td width="50%">The amount of space in pixels to leave on each side of the menu item
      contents.</td></tr>
<tr><td width="40%">item_icon_space</td><td width="50%">The space between an item&rsquo;s icon and the title text, in pixels.</td></tr>
<tr><td width="40%">item_spacing</td><td width="50%">The amount of space to leave between menu items, in pixels.</td></tr>
<tr><td width="40%">menu_pixmap_style</td><td width="50%">The image file pattern for the menu frame styled box.
      Example:  &ldquo;menu_*.png&ldquo; (this will use images such as &ldquo;menu_c.png&ldquo;,
      &ldquo;menu_w.png&ldquo;, &lsquo;menu_nw.png&ldquo;, etc.)</td></tr>
<tr><td width="40%">item_pixmap_style</td><td width="50%">The image file pattern for the item styled box.</td></tr>
<tr><td width="40%">selected_item_pixmap_style</td><td width="50%">The image file pattern for the selected item highlight styled box.</td></tr>
<tr><td width="40%">scrollbar</td><td width="50%">Boolean value indicating whether the scroll bar should be drawn if the
      frame and thumb styled boxes are configured.</td></tr>
<tr><td width="40%">scrollbar_frame</td><td width="50%">The image file pattern for the entire scroll bar.
      Example:  &ldquo;scrollbar_*.png&ldquo;</td></tr>
<tr><td width="40%">scrollbar_thumb</td><td width="50%">The image file pattern for the scroll bar thumb (the part of the scroll
      bar that moves as scrolling occurs).
      Example:  &ldquo;scrollbar_thumb_*.png&ldquo;</td></tr>
<tr><td width="40%">scrollbar_thumb_overlay</td><td width="50%">If this option is set to &ldquo;true&ldquo; then the scrollbar thumb
      side slices (every slice except the center slice) will overlay the
      scrollbar frame side slices. And the center slice of the scrollbar_thumb
      can move all the way (from top to bottom), being drawn on the center
      slice of the scrollbar frame. That way we can make a scrollbar with
      round-shaped edges so there won&rsquo;t be a free space from the thumb to
      the frame in top and bottom scrollbar positions. Default is &ldquo;false&ldquo;.</td></tr>
<tr><td width="40%">scrollbar_slice</td><td width="50%">The menu frame styled box&rsquo;s slice in which the scrollbar will be
      drawn. Possible values are &ldquo;west&ldquo;, &ldquo;center&ldquo;, &ldquo;east&ldquo; (default).
      &ldquo;west&ldquo; - the scrollbar will be drawn in the west slice (right-aligned).
      &ldquo;east&ldquo; - the scrollbar will be drawn in the east slice (left-aligned).
      &ldquo;center&ldquo; - the scrollbar will be drawn in the center slice.
      Note: in case of &ldquo;center&ldquo; slice:
      a) If the scrollbar should be drawn then boot menu entry&rsquo;s width is
      decreased by the scrollbar&rsquo;s width and the scrollbar is drawn at the
      right side of the center slice.
      b) If the scrollbar won&rsquo;t be drawn then the boot menu entry&rsquo;s width
      is the width of the center slice.
      c) We don&rsquo;t necessary need the menu pixmap box to display the scrollbar.</td></tr>
<tr><td width="40%">scrollbar_left_pad</td><td width="50%">The left scrollbar padding in pixels.
      Unused if &ldquo;scrollbar_slice&ldquo; is &ldquo;west&ldquo;.</td></tr>
<tr><td width="40%">scrollbar_right_pad</td><td width="50%">The right scrollbar padding in pixels.
      Unused if &ldquo;scrollbar_slice&ldquo; is &ldquo;east&ldquo;.</td></tr>
<tr><td width="40%">scrollbar_top_pad</td><td width="50%">The top scrollbar padding in pixels.</td></tr>
<tr><td width="40%">scrollbar_bottom_pad</td><td width="50%">The bottom scrollbar padding in pixels.</td></tr>
<tr><td width="40%">visible</td><td width="50%">Set to &ldquo;false&ldquo; to hide the boot menu.</td></tr>
</tbody>
</table>

</li><li>canvas
   Canvas is a container that allows manual placement of components within it.
   It does not alter the positions of its child components.  It assigns all
   child components their preferred sizes.

</li><li>hbox
   The *hbox* container lays out its children from left to right, giving each
   one its preferred width.  The height of each child is set to the maximum of
   the preferred heights of all children.
   
</li><li>vbox
   The *vbox* container lays out its children from top to bottom, giving each
   one its preferred height.  The width of each child is set to the maximum of
   the preferred widths of all children.
</li></ul>

</div>
<div class="subsection-level-extent" id="Common-properties">
<h4 class="subsection"><span>7.3.6 Common properties<a class="copiable-link" href="#Common-properties"> &para;</a></span></h4>

<p>The following properties are supported by all components:
</p><dl class="table">
<dt>&lsquo;<samp class="samp">left</samp>&rsquo;</dt>
<dd><p>The distance from the left border of container to left border of the object in either of three formats:
        </p><table class="multitable">
<tbody><tr><td width="20%">x</td><td width="70%">Value in pixels</td></tr>
<tr><td width="20%">p%</td><td width="70%">Percentage</td></tr>
<tr><td width="20%">p%+x</td><td width="70%">mixture of both</td></tr>
</tbody>
</table>
</dd>
<dt>&lsquo;<samp class="samp">top</samp>&rsquo;</dt>
<dd><p>The distance from the left border of container to left border of the object in same format.
</p></dd>
<dt>&lsquo;<samp class="samp">width</samp>&rsquo;</dt>
<dd><p>The width of object in same format.
</p></dd>
<dt>&lsquo;<samp class="samp">height</samp>&rsquo;</dt>
<dd><p>The height of object in same format.
</p></dd>
<dt>&lsquo;<samp class="samp">id</samp>&rsquo;</dt>
<dd><p>The identifier for the component.  This can be any arbitrary string.
   The ID can be used by scripts to refer to various components in the GUI
   component tree.  Currently, there is one special ID value that GRUB
   recognizes:
</p>
<table class="multitable">
<tbody><tr><td width="20%">&ldquo;__timeout__&ldquo;</td><td width="70%">Component with this ID will be updated by GRUB and will indicate
      time elapsed to an automatical boot of the default entry.
      Affected components: &ldquo;label&ldquo;, &ldquo;circular_progress&ldquo;, &ldquo;progress_bar&ldquo;.</td></tr>
</tbody>
</table>
</dd>
</dl>

<hr>
</div>
</div>
</div>
<div class="chapter-level-extent" id="Network">
<div class="nav-panel">
<p>
Next: <a href="#Serial-terminal" accesskey="n" rel="next">Using GRUB via a serial line</a>, Previous: <a href="#Theme-file-format" accesskey="p" rel="prev">Theme file format</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Booting-GRUB-from-the-network"><span>8 Booting GRUB from the network<a class="copiable-link" href="#Booting-GRUB-from-the-network"> &para;</a></span></h2>

<p>The following instructions don&rsquo;t work for *-emu, i386-qemu, i386-coreboot,
i386-multiboot, mips_loongson, mips-arc and mips_qemu_mips
</p>
<p>To generate a netbootable directory, run:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">grub-mknetdir --net-directory=/srv/tftp --subdir=/boot/grub -d /usr/lib/grub/&lt;platform&gt;
</pre></div></div>

<p>E.g. for i386-pc:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">grub-mknetdir --net-directory=/srv/tftp --subdir=/boot/grub -d /usr/lib/grub/i386-pc
</pre></div></div>

<p>Then follow instructions printed out by grub2-mknetdir on configuring your DHCP
server.
</p>
<p>The grub.cfg file is placed in the same directory as the path output by
grub-mknetdir hereafter referred to as FWPATH. GRUB will search for its
configuration files in order using the following rules where the appended
value corresponds to a value on the client machine.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-&lsquo;<samp class="samp">(UUID OF MACHINE)</samp>&rsquo;
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-&lsquo;<samp class="samp">(MAC ADDRESS OF NIC)</samp>&rsquo;
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-&lsquo;<samp class="samp">(IPv4 OR IPv6 ADDRESS)</samp>&rsquo;
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg
</pre></div></div>

<p>The UUID is the Client Machine Identifier Option Definition as specified in
RFC 4578. The client will only attempt to loouk up a UUID config file if it
was provided by the DHCP server.
</p>
<p>The client will only attempt to look up an IPv6 address config once, however,
it will try the IPv4 multiple times. The concrete example below shows what
would happen under the IPv4 case.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">UUID: 7726a678-7fc0-4853-a4f6-c85ac36a120a
MAC:  52:54:00:ec:33:81
IPV4: 10.0.0.130 (0A000082)
</pre></div></div>

<div class="example">
<div class="group"><pre class="example-preformatted">&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-7726a678-7fc0-4853-a4f6-c85ac36a120a
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-52-54-00-ec-33-81
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0A000082
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0A00008
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0A0000
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0A000
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0A00
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0A0
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0A
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg-0
&lsquo;<samp class="samp">(FWPATH)</samp>&rsquo;/grub.cfg
</pre></div></div>

<p>This feature is enabled by default but it can be disabled by setting the
&lsquo;<samp class="samp">feature_net_search_cfg</samp>&rsquo; to &lsquo;<samp class="samp">n</samp>&rsquo;. Since this happens before the
configuration file is read by GRUB, this option has to be disabled in an
embedded configuration file (see <a class="pxref" href="#Embedded-configuration">Embedding a configuration file into GRUB</a>).
</p>
<p>After GRUB has started, files on the TFTP server will be accessible via the
&lsquo;<samp class="samp">(tftp)</samp>&rsquo; device.
</p>
<p>The server IP address can be controlled by changing the
&lsquo;<samp class="samp">(tftp)</samp>&rsquo; device name to &lsquo;<samp class="samp">(tftp,<var class="var">server-ip</var>)</samp>&rsquo;. Note that
this should be changed both in the prefix and in any references to the
device name in the configuration file.
</p>
<p>GRUB provides several environment variables which may be used to inspect or
change the behaviour of the PXE device. In the following description
<var class="var">&lt;interface&gt;</var> is placeholder for the name of network interface (platform
dependent):
</p>
<dl class="table">
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_ip</samp>&rsquo;</dt>
<dd><p>The network interface&rsquo;s IP address.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_mac</samp>&rsquo;</dt>
<dd><p>The network interface&rsquo;s MAC address.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_clientid</samp>&rsquo;</dt>
<dd><p>The client id provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_clientuuid</samp>&rsquo;</dt>
<dd><p>The client uuid provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_hostname</samp>&rsquo;</dt>
<dd><p>The client host name provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_domain</samp>&rsquo;</dt>
<dd><p>The client domain name provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_rootpath</samp>&rsquo;</dt>
<dd><p>The path to the client&rsquo;s root disk provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_extensionspath</samp>&rsquo;</dt>
<dd><p>The path to additional DHCP vendor extensions provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_boot_file</samp>&rsquo;</dt>
<dd><p>The boot file name provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_dhcp_server_name</samp>&rsquo;</dt>
<dd><p>The name of the DHCP server responsible for these boot parameters.
Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_<var class="var">&lt;interface&gt;</var>_next_server</samp>&rsquo;</dt>
<dd><p>The IP address of the next (usually, TFTP) server provided by DHCP.
Read-only.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_default_interface</samp>&rsquo;</dt>
<dd><p>Initially set to name of network interface that was used to load grub.
Read-write, although setting it affects only interpretation of
&lsquo;<samp class="samp">net_default_ip</samp>&rsquo; and &lsquo;<samp class="samp">net_default_mac</samp>&rsquo;
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_default_ip</samp>&rsquo;</dt>
<dd><p>The IP address of default interface.  Read-only. This is alias for the
&lsquo;<samp class="samp">net_${net_default_interface}_ip</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_default_mac</samp>&rsquo;</dt>
<dd><p>The default interface&rsquo;s MAC address.  Read-only.  This is alias for the
&lsquo;<samp class="samp">net_${net_default_interface}_mac</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp class="samp">net_default_server</samp>&rsquo;</dt>
<dd><p>The default server used by network drives (see <a class="pxref" href="#Device-syntax">How to specify devices</a>).  Read-write,
although setting this is only useful before opening a network device.
</p>
</dd>
</dl>

<hr>
</div>
<div class="chapter-level-extent" id="Serial-terminal">
<div class="nav-panel">
<p>
Next: <a href="#Vendor-power_002don-keys" accesskey="n" rel="next">Using GRUB with vendor power-on keys</a>, Previous: <a href="#Network" accesskey="p" rel="prev">Booting GRUB from the network</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Using-GRUB-via-a-serial-line"><span>9 Using GRUB via a serial line<a class="copiable-link" href="#Using-GRUB-via-a-serial-line"> &para;</a></span></h2>

<p>This chapter describes how to use the serial terminal support in GRUB.
</p>
<p>If you have many computers or computers with no display/keyboard, it
could be very useful to control the computers through serial
communications. To connect one computer with another via a serial line,
you need to prepare a null-modem (cross) serial cable, and you may need
to have multiport serial boards, if your computer doesn&rsquo;t have extra
serial ports. In addition, a terminal emulator is also required, such as
minicom. Refer to a manual of your operating system, for more
information.
</p>
<p>As for GRUB, the instruction to set up a serial terminal is quite
simple.  Here is an example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">grub&gt; <kbd class="kbd">serial --unit=0 --speed=9600</kbd>
grub&gt; <kbd class="kbd">terminal_input serial; terminal_output serial</kbd>
</pre></div></div>

<p>The command <code class="command">serial</code> initializes the serial unit 0 with the
speed 9600bps. The serial unit 0 is usually called &lsquo;<samp class="samp">COM1</samp>&rsquo;, so, if
you want to use COM2, you must specify &lsquo;<samp class="samp">--unit=1</samp>&rsquo; instead. This
command accepts many other options, see <a class="pxref" href="#serial">serial</a> for more details.
</p>
<p>Without argument or with &lsquo;<samp class="samp">--port=auto</samp>&rsquo;, GRUB will attempt to use
ACPI when available to auto-detect the default serial port and its
configuration.
</p>
<p>The commands <code class="command">terminal_input</code> (see <a class="pxref" href="#terminal_005finput">terminal_input</a>) and
<code class="command">terminal_output</code> (see <a class="pxref" href="#terminal_005foutput">terminal_output</a>) choose which type of
terminal you want to use. In the case above, the terminal will be a
serial terminal, but you can also pass <code class="code">console</code> to the command,
as &lsquo;<samp class="samp">terminal_input serial console</samp>&rsquo;. In this case, a terminal in which
you press any key will be selected as a GRUB terminal. In the example above,
note that you need to put both commands on the same command line, as you
will lose the ability to type commands on the console after the first
command.
</p>
<p>However, note that GRUB assumes that your terminal emulator is
compatible with VT100 by default. This is true for most terminal
emulators nowadays, but you should pass the option <samp class="option">--dumb</samp> to
the command if your terminal emulator is not VT100-compatible or
implements few VT100 escape sequences. If you specify this option then
GRUB provides you with an alternative menu interface, because the normal
menu requires several fancy features of your terminal.
</p>

<hr>
</div>
<div class="chapter-level-extent" id="Vendor-power_002don-keys">
<div class="nav-panel">
<p>
Next: <a href="#Images" accesskey="n" rel="next">GRUB image files</a>, Previous: <a href="#Serial-terminal" accesskey="p" rel="prev">Using GRUB via a serial line</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Using-GRUB-with-vendor-power_002don-keys"><span>10 Using GRUB with vendor power-on keys<a class="copiable-link" href="#Using-GRUB-with-vendor-power_002don-keys"> &para;</a></span></h2>

<p>Some laptop vendors provide an additional power-on button which boots
another OS.  GRUB supports such buttons with the &lsquo;<samp class="samp">GRUB_TIMEOUT_BUTTON</samp>&rsquo;,
&lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE_BUTTON</samp>&rsquo;, &lsquo;<samp class="samp">GRUB_DEFAULT_BUTTON</samp>&rsquo;, and
&lsquo;<samp class="samp">GRUB_BUTTON_CMOS_ADDRESS</samp>&rsquo; variables in default/grub (see <a class="pxref" href="#Simple-configuration">Simple configuration handling</a>).  &lsquo;<samp class="samp">GRUB_TIMEOUT_BUTTON</samp>&rsquo;,
&lsquo;<samp class="samp">GRUB_TIMEOUT_STYLE_BUTTON</samp>&rsquo;, and &lsquo;<samp class="samp">GRUB_DEFAULT_BUTTON</samp>&rsquo; are used
instead of the corresponding variables without the &lsquo;<samp class="samp">_BUTTON</samp>&rsquo; suffix
when powered on using the special button.  &lsquo;<samp class="samp">GRUB_BUTTON_CMOS_ADDRESS</samp>&rsquo;
is vendor-specific and partially model-specific.  Values known to the GRUB
team are:
</p>
<dl class="table">
<dt><kbd class="key">Dell XPS M1330M</kbd></dt>
<dd><p>121:3
</p></dd>
<dt><kbd class="key">Dell XPS M1530</kbd></dt>
<dd><p>85:3
</p></dd>
<dt><kbd class="key">Dell Latitude E4300</kbd></dt>
<dd><p>85:3
</p></dd>
<dt><kbd class="key">Asus EeePC 1005PE</kbd></dt>
<dd><p>84:1 (unconfirmed)
</p></dd>
<dt><kbd class="key">LENOVO ThinkPad T410s (2912W1C)</kbd></dt>
<dd><p>101:3
</p></dd>
</dl>

<p>To take full advantage of this function, install GRUB into the MBR
(see <a class="pxref" href="#Installing-GRUB-using-grub2_002dinstall">Installing GRUB using grub2-install</a>).
</p>
<p>If you have a laptop which has a similar feature and not in the above list
could you figure your address and contribute?
To discover the address do the following:
</p><ul class="itemize mark-bullet">
<li>boot normally
</li><li><div class="example">
<pre class="example-preformatted">sudo modprobe nvram
sudo cat /dev/nvram | xxd &gt; normal_button.txt
</pre></div>
</li><li>boot using vendor button
</li><li><div class="example">
<pre class="example-preformatted">sudo modprobe nvram
sudo cat /dev/nvram | xxd &gt; normal_vendor.txt
</pre></div>
</li></ul>

<p>Then compare these text files and find where a bit was toggled. E.g. in
case of Dell XPS it was:
</p><div class="example">
<pre class="example-preformatted">byte 0x47: 20 --&gt; 28
</pre></div>
<p>It&rsquo;s a bit number 3 as seen from following table:
</p><table class="multitable">
<tbody><tr><td width="20%">0</td><td width="20%">01</td></tr>
<tr><td width="20%">1</td><td width="20%">02</td></tr>
<tr><td width="20%">2</td><td width="20%">04</td></tr>
<tr><td width="20%">3</td><td width="20%">08</td></tr>
<tr><td width="20%">4</td><td width="20%">10</td></tr>
<tr><td width="20%">5</td><td width="20%">20</td></tr>
<tr><td width="20%">6</td><td width="20%">40</td></tr>
<tr><td width="20%">7</td><td width="20%">80</td></tr>
</tbody>
</table>

<p>0x47 is decimal 71. Linux nvram implementation cuts first 14 bytes of
CMOS. So the real byte address in CMOS is 71+14=85
So complete address is 85:3
</p>
<hr>
</div>
<div class="chapter-level-extent" id="Images">
<div class="nav-panel">
<p>
Next: <a href="#Core-image-size-limitation" accesskey="n" rel="next">Core image size limitation</a>, Previous: <a href="#Vendor-power_002don-keys" accesskey="p" rel="prev">Using GRUB with vendor power-on keys</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="GRUB-image-files"><span>11 GRUB image files<a class="copiable-link" href="#GRUB-image-files"> &para;</a></span></h2>

<p>GRUB consists of several images: a variety of bootstrap images for starting
GRUB in various ways, a kernel image, and a set of modules which are
combined with the kernel image to form a core image.  Here is a short
overview of them.
</p>
<dl class="table">
<dt><samp class="file">boot.img</samp></dt>
<dd><p>On PC BIOS systems, this image is the first part of GRUB to start.  It is
written to a master boot record (MBR) or to the boot sector of a partition.
Because a PC boot sector is 512 bytes, the size of this image is exactly 512
bytes.
</p>
<p>The sole function of <samp class="file">boot.img</samp> is to read the first sector of the core
image from a local disk and jump to it.  Because of the size restriction,
<samp class="file">boot.img</samp> cannot understand any file system structure, so
<code class="command">grub2-install</code> hardcodes the location of the first sector of the
core image into <samp class="file">boot.img</samp> when installing GRUB.
</p>
</dd>
<dt><samp class="file">diskboot.img</samp></dt>
<dd><p>This image is used as the first sector of the core image when booting from a
hard disk.  It reads the rest of the core image into memory and starts the
kernel.  Since file system handling is not yet available, it encodes the
location of the core image using a block list format.
</p>
</dd>
<dt><samp class="file">cdboot.img</samp></dt>
<dd><p>This image is used as the first sector of the core image when booting from a
CD-ROM drive.  It performs a similar function to <samp class="file">diskboot.img</samp>.
</p>
</dd>
<dt><samp class="file">pxeboot.img</samp></dt>
<dd><p>This image is used as the start of the core image when booting from the
network using PXE.  See <a class="xref" href="#Network">Booting GRUB from the network</a>.
</p>
</dd>
<dt><samp class="file">lnxboot.img</samp></dt>
<dd><p>This image may be placed at the start of the core image in order to make
GRUB look enough like a Linux kernel that it can be booted by LILO using an
&lsquo;<samp class="samp">image=</samp>&rsquo; section.
</p>
</dd>
<dt><samp class="file">kernel.img</samp></dt>
<dd><p>This image contains GRUB&rsquo;s basic run-time facilities: frameworks for device
and file handling, environment variables, the rescue mode command-line
parser, and so on.  It is rarely used directly, but is built into all core
images.
</p>
</dd>
<dt><samp class="file">core.img</samp></dt>
<dd><p>This is the core image of GRUB.  It is built dynamically from the kernel
image and an arbitrary list of modules by the <code class="command">grub2-mkimage</code>
program.  Usually, it contains enough modules to access <samp class="file">/boot/grub</samp>,
and loads everything else (including menu handling, the ability to load
target operating systems, and so on) from the file system at run-time.  The
modular design allows the core image to be kept small, since the areas of
disk where it must be installed are often as small as 32KB.
</p>
<p>See <a class="xref" href="#BIOS-installation">BIOS installation</a>, for details on where the core image can be
installed on PC systems.
</p>
</dd>
<dt><samp class="file">*.mod</samp></dt>
<dd><p>Everything else in GRUB resides in dynamically loadable modules.  These are
often loaded automatically, or built into the core image if they are
essential, but may also be loaded manually using the <code class="command">insmod</code>
command (see <a class="pxref" href="#insmod">insmod</a>).
</p></dd>
</dl>

<h3 class="heading" id="For-GRUB-Legacy-users"><span>For GRUB Legacy users<a class="copiable-link" href="#For-GRUB-Legacy-users"> &para;</a></span></h3>

<p>GRUB 2 has a different design from GRUB Legacy, and so correspondences with
the images it used cannot be exact.  Nevertheless, GRUB Legacy users often
ask questions in the terms they are familiar with, and so here is a brief
guide to how GRUB 2&rsquo;s images relate to that.
</p>
<dl class="table">
<dt><samp class="file">stage1</samp></dt>
<dd><p>Stage 1 from GRUB Legacy was very similar to <samp class="file">boot.img</samp> in GRUB 2, and
they serve the same function.
</p>
</dd>
<dt><samp class="file">*_stage1_5</samp></dt>
<dd><p>In GRUB Legacy, Stage 1.5&rsquo;s function was to include enough filesystem code
to allow the much larger Stage 2 to be read from an ordinary filesystem.  In
this respect, its function was similar to <samp class="file">core.img</samp> in GRUB 2.
However, <samp class="file">core.img</samp> is much more capable than Stage 1.5 was; since it
offers a rescue shell, it is sometimes possible to recover manually in the
event that it is unable to load any other modules, for example if partition
numbers have changed.  <samp class="file">core.img</samp> is built in a more flexible way,
allowing GRUB 2 to support reading modules from advanced disk types such as
LVM and RAID.
</p>
<p>GRUB Legacy could run with only Stage 1 and Stage 2 in some limited
configurations, while GRUB 2 requires <samp class="file">core.img</samp> and cannot work
without it.
</p>
</dd>
<dt><samp class="file">stage2</samp></dt>
<dd><p>GRUB 2 has no single Stage 2 image.  Instead, it loads modules from
<samp class="file">/boot/grub</samp> at run-time.
</p>
</dd>
<dt><samp class="file">stage2_eltorito</samp></dt>
<dd><p>In GRUB 2, images for booting from CD-ROM drives are now constructed using
<samp class="file">cdboot.img</samp> and <samp class="file">core.img</samp>, making sure that the core image
contains the &lsquo;<samp class="samp">iso9660</samp>&rsquo; module.  It is usually best to use the
<code class="command">grub2-mkrescue</code> program for this.
</p>
</dd>
<dt><samp class="file">nbgrub</samp></dt>
<dd><p>There is as yet no equivalent for <samp class="file">nbgrub</samp> in GRUB 2; it was used by
Etherboot and some other network boot loaders.
</p>
</dd>
<dt><samp class="file">pxegrub</samp></dt>
<dd><p>In GRUB 2, images for PXE network booting are now constructed using
<samp class="file">pxeboot.img</samp> and <samp class="file">core.img</samp>, making sure that the core image
contains the &lsquo;<samp class="samp">pxe</samp>&rsquo; and &lsquo;<samp class="samp">pxecmd</samp>&rsquo; modules.  See <a class="xref" href="#Network">Booting GRUB from the network</a>.
</p></dd>
</dl>

<hr>
</div>
<div class="chapter-level-extent" id="Core-image-size-limitation">
<div class="nav-panel">
<p>
Next: <a href="#Filesystem" accesskey="n" rel="next">Filesystem syntax and semantics</a>, Previous: <a href="#Images" accesskey="p" rel="prev">GRUB image files</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Core-image-size-limitation-1"><span>12 Core image size limitation<a class="copiable-link" href="#Core-image-size-limitation-1"> &para;</a></span></h2>

<p>Heavily limited platforms:
</p><ul class="itemize mark-bullet">
<li>i386-pc (normal and PXE): the core image size (compressed) is limited by 458240 bytes.
 kernel.img (.text + .data + .bss, uncompressed) is limited by 392704 bytes.
 module size (uncompressed) + kernel.img (.text + .data, uncompressed) is limited by the size of contiguous chunk at 1M address.
</li><li>sparc64-ieee1275: kernel.img (.text + .data + .bss) + modules + 256K (stack) + 2M (heap) is limited by space available at 0x4400. On most platforms it&rsquo;s just 3 or 4M since ieee1275 maps only so much.
</li><li>i386-ieee1275: kernel.img  (.text + .data + .bss) + modules is limited by memory available at 0x10000, at most 596K
</li></ul>

<p>Lightly limited platforms:
</p>
<ul class="itemize mark-bullet">
<li>*-xen: limited only by adress space and RAM size.
</li><li>i386-qemu: kernel.img (.text + .data + .bss) is limited by 392704 bytes.
                 (core.img would be limited by ROM size but it&rsquo;s unlimited on qemu
</li><li>All EFI platforms: limited by contiguous RAM size and possibly firmware bugs
</li><li>Coreboot and multiboot. kernel.img (.text + .data + .bss) is limited by 392704 bytes.
      module size is limited by the size of contiguous chunk at 1M address.
</li><li>mipsel-loongson (ELF), mips(el)-qemu_mips (ELF): if uncompressed:
                kernel.img (.text + .data) + modules is limited by the space from 80200000 forward
                if compressed:
                kernel.img (.text + .data, uncompressed) + modules (uncompressed)
                + (modules + kernel.img (.text + .data)) (compressed)
                + decompressor is limited by the space from 80200000 forward
</li><li>mipsel-loongson (Flash), mips(el)-qemu_mips (Flash): kernel.img (.text + .data) + modules is limited by the space from 80200000 forward
                               core.img (final) is limited by flash size (512K on yeeloong and fulooong)
</li><li>mips-arc: if uncompressed:
                kernel.img (.text + .data) is limited by the space from 8bd00000 forward
                modules + dummy decompressor  is limited by the space from 8bd00000 backward
                if compressed:
                kernel.img (.text + .data, uncompressed) is limited by the space from 8bd00000 forward
                modules (uncompressed) + (modules + kernel.img (.text + .data)) (compressed, aligned to 1M)
                + 1M (decompressor + scratch space) is limited by the space from 8bd00000 backward
</li><li>powerpc-ieee1275: kernel.img (.text + .data + .bss) + modules is limited by space available at 0x200000
</li></ul>

<hr>
</div>
<div class="chapter-level-extent" id="Filesystem">
<div class="nav-panel">
<p>
Next: <a href="#Interface" accesskey="n" rel="next">GRUB&rsquo;s user interface</a>, Previous: <a href="#Core-image-size-limitation" accesskey="p" rel="prev">Core image size limitation</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="Filesystem-syntax-and-semantics"><span>13 Filesystem syntax and semantics<a class="copiable-link" href="#Filesystem-syntax-and-semantics"> &para;</a></span></h2>

<p>GRUB uses a special syntax for specifying disk drives which can be
accessed by BIOS. Because of BIOS limitations, GRUB cannot distinguish
between IDE, ESDI, SCSI, or others. You must know yourself which BIOS
device is equivalent to which OS device. Normally, that will be clear if
you see the files in a device or use the command <code class="command">search</code>
(see <a class="pxref" href="#search">search</a>).
</p>

<ul class="mini-toc">
<li><a href="#Device-syntax" accesskey="1">How to specify devices</a></li>
<li><a href="#File-name-syntax" accesskey="2">How to specify files</a></li>
<li><a href="#Block-list-syntax" accesskey="3">How to specify block lists</a></li>
</ul>
<hr>
<div class="section-level-extent" id="Device-syntax">
<div class="nav-panel">
<p>
Next: <a href="#File-name-syntax" accesskey="n" rel="next">How to specify files</a>, Up: <a href="#Filesystem" accesskey="u" rel="up">Filesystem syntax and semantics</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="How-to-specify-devices"><span>13.1 How to specify devices<a class="copiable-link" href="#How-to-specify-devices"> &para;</a></span></h3>

<p>The device syntax is like this:
</p>
<div class="example">
<pre class="example-preformatted"><code class="code">(<var class="var">device</var>[,<var class="var">partmap-name1</var><var class="var">part-num1</var>[,<var class="var">partmap-name2</var><var class="var">part-num2</var>[,...]]])</code>
</pre></div>

<p>&lsquo;<samp class="samp">[]</samp>&rsquo; means the parameter is optional. <var class="var">device</var> depends on the disk
driver in use. BIOS and EFI disks use either &lsquo;<samp class="samp">fd</samp>&rsquo; or &lsquo;<samp class="samp">hd</samp>&rsquo; followed
by a digit, like &lsquo;<samp class="samp">fd0</samp>&rsquo;, or &lsquo;<samp class="samp">cd</samp>&rsquo;.
AHCI, PATA (ata), crypto, USB use the name of driver followed by a number.
Memdisk and host are limited to one disk and so it&rsquo;s refered just by driver
name.
RAID (md), ofdisk (ieee1275 and nand), LVM (lvm), LDM, virtio (vdsk)
and arcdisk (arc) use intrinsic name of disk prefixed by driver name.
Additionally just &ldquo;nand&rdquo; refers to the disk aliased as &ldquo;nand&rdquo;.
Conflicts are solved by suffixing a number if necessarry.
Commas need to be escaped.
Loopback uses whatever name specified to <code class="command">loopback</code> command.
Hostdisk uses names specified in device.map as long as it&rsquo;s of the form
[fhc]d[0-9]* or hostdisk/&lt;OS DEVICE&gt;.
For crypto and RAID (md) additionally you can use the syntax
&lt;driver name&gt;uuid/&lt;uuid&gt;.  For LVM additionally you can use the syntax
lvmid/&lt;volume-group-uuid&gt;/&lt;volume-uuid&gt;.
</p>
<div class="example">
<pre class="example-preformatted">(fd0)
(hd0)
(cd)
(ahci0)
(ata0)
(crypto0)
(usb0)
(cryptouuid/123456789abcdef0123456789abcdef0)
(mduuid/123456789abcdef0123456789abcdef0)
(lvm/system-root)
(lvmid/F1ikgD-2RES-306G-il9M-7iwa-4NKW-EbV1NV/eLGuCQ-L4Ka-XUgR-sjtJ-ffch-bajr-fCNfz5)
(md/myraid)
(md/0)
(ieee1275/disk2)
(ieee1275//pci@1f\,0/ide@d/disk@2)
(nand)
(memdisk)
(host)
(myloop)
(hostdisk//dev/sda)
</pre></div>

<p><var class="var">part-num</var> represents the partition number of <var class="var">device</var>, starting
from one. <var class="var">partname</var> is optional but is recommended since disk may have
several top-level partmaps. Specifying third and later component you can access
to subpartitions.
</p>
<p>The syntax &lsquo;<samp class="samp">(hd0)</samp>&rsquo; represents using the entire disk (or the
MBR when installing GRUB), while the syntax &lsquo;<samp class="samp">(hd0,1)</samp>&rsquo;
represents using the first partition of the disk (or the boot sector
of the partition when installing GRUB).
</p>
<div class="example">
<pre class="example-preformatted">(hd0,msdos1)
(hd0,msdos1,msdos5)
(hd0,msdos1,bsd3)
(hd0,netbsd1)
(hd0,gpt1)
(hd0,1,3)
</pre></div>

<p>If you enabled the network support, the special drives
<code class="code">(<var class="var">protocol</var>[,<var class="var">server</var>])</code> are also available. Supported protocols
are &lsquo;<samp class="samp">http</samp>&rsquo; and &lsquo;<samp class="samp">tftp</samp>&rsquo;. If <var class="var">server</var> is omitted, value of
environment variable &lsquo;<samp class="samp">net_default_server</samp>&rsquo; is used.
Before using the network drive, you must initialize the network.
See <a class="xref" href="#Network">Booting GRUB from the network</a>, for more information.
</p>
<p>When using &lsquo;<samp class="samp">http</samp>&rsquo; or &lsquo;<samp class="samp">tftp</samp>&rsquo;, ports other than &lsquo;<samp class="samp">80</samp>&rsquo; can be
specified using a colon (&lsquo;<samp class="samp">:</samp>&rsquo;) after the address.  To avoid parsing
conflicts, when using IPv6 addresses with custom ports, the addresses
must be enclosed with square brackets (&lsquo;<samp class="samp">[]</samp>&rsquo;), as is standard
practice.
</p>
<div class="example">
<pre class="example-preformatted">(http,grub.example.com:31337)
(http,192.0.2.1:339)
(http,[2001:db8::1]:11235)
</pre></div>

<p>If you boot GRUB from a CD-ROM, &lsquo;<samp class="samp">(cd)</samp>&rsquo; is available. See <a class="xref" href="#Making-a-GRUB-bootable-CD_002dROM">Making a GRUB bootable CD-ROM</a>, for details.
</p>

<hr>
</div>
<div class="section-level-extent" id="File-name-syntax">
<div class="nav-panel">
<p>
Next: <a href="#Block-list-syntax" accesskey="n" rel="next">How to specify block lists</a>, Previous: <a href="#Device-syntax" accesskey="p" rel="prev">How to specify devices</a>, Up: <a href="#Filesystem" accesskey="u" rel="up">Filesystem syntax and semantics</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="How-to-specify-files"><span>13.2 How to specify files<a class="copiable-link" href="#How-to-specify-files"> &para;</a></span></h3>

<p>There are two ways to specify files, by <em class="dfn">absolute file name</em> and by
<em class="dfn">block list</em>.
</p>
<p>An absolute file name resembles a Unix absolute file name, using
&lsquo;<samp class="samp">/</samp>&rsquo; for the directory separator (not &lsquo;<samp class="samp">\</samp>&rsquo; as in DOS). One
example is &lsquo;<samp class="samp">(hd0,1)/boot/grub2/grub.cfg</samp>&rsquo;. This means the file
<samp class="file">/boot/grub2/grub.cfg</samp> in the first partition of the first hard
disk. If you omit the device name in an absolute file name, GRUB uses
GRUB&rsquo;s <em class="dfn">root device</em> implicitly. So if you set the root device to,
say, &lsquo;<samp class="samp">(hd1,1)</samp>&rsquo; by the command &lsquo;<samp class="samp">set root=(hd1,1)</samp>&rsquo; (see <a class="pxref" href="#set">set</a>),
then <code class="code">/boot/kernel</code> is the same as <code class="code">(hd1,1)/boot/kernel</code>.
</p>
<p>On ZFS filesystem the first path component must be
<var class="var">volume</var>&lsquo;<samp class="samp">@</samp>&rsquo;[<var class="var">snapshot</var>].
So &lsquo;<samp class="samp">/rootvol@snap-129/boot/grub2/grub.cfg</samp>&rsquo; refers to file
&lsquo;<samp class="samp">/boot/grub2/grub.cfg</samp>&rsquo; in snapshot of volume &lsquo;<samp class="samp">rootvol</samp>&rsquo; with name
&lsquo;<samp class="samp">snap-129</samp>&rsquo;.  Trailing &lsquo;<samp class="samp">@</samp>&rsquo; after volume name is mandatory even if
snapshot name is omitted.
</p>

<hr>
</div>
<div class="section-level-extent" id="Block-list-syntax">
<div class="nav-panel">
<p>
Previous: <a href="#File-name-syntax" accesskey="p" rel="prev">How to specify files</a>, Up: <a href="#Filesystem" accesskey="u" rel="up">Filesystem syntax and semantics</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="How-to-specify-block-lists"><span>13.3 How to specify block lists<a class="copiable-link" href="#How-to-specify-block-lists"> &para;</a></span></h3>

<p>A block list is used for specifying a file that doesn&rsquo;t appear in the
filesystem, like a chainloader. The syntax is
<code class="code">[<var class="var">offset</var>]+[<var class="var">length</var>][,[<var class="var">offset</var>]+[<var class="var">length</var>]]&hellip;</code>.
Here is an example:
</p>
<div class="example">
<pre class="example-preformatted"><code class="code">0+100,200+1,300+300,800+</code>
</pre></div>

<p>This represents that GRUB should read blocks 0 through 99, block 200,
blocks 300 through 599, and blocks 800 until the end of the device.
If you omit an offset, then GRUB assumes the offset is zero. If the
length is omitted, then GRUB assumes the block list extends until the
end of the device.
</p>
<p>Like the file name syntax (see <a class="pxref" href="#File-name-syntax">How to specify files</a>), if a blocklist
does not contain a device name, then GRUB uses GRUB&rsquo;s <em class="dfn">root
device</em>. So <code class="code">(hd0,2)+1</code> is the same as <code class="code">+1</code> when the root
device is &lsquo;<samp class="samp">(hd0,2)</samp>&rsquo;.
</p>

<hr>
</div>
</div>
<div class="chapter-level-extent" id="Interface">
<div class="nav-panel">
<p>
Next: <a href="#Environment" accesskey="n" rel="next">GRUB environment variables</a>, Previous: <a href="#Filesystem" accesskey="p" rel="prev">Filesystem syntax and semantics</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="GRUB_0027s-user-interface"><span>14 GRUB&rsquo;s user interface<a class="copiable-link" href="#GRUB_0027s-user-interface"> &para;</a></span></h2>

<p>GRUB has both a simple menu interface for choosing preset entries from a
configuration file, and a highly flexible command-line for performing
any desired combination of boot commands.
</p>
<p>GRUB looks for its configuration file as soon as it is loaded. If one
is found, then the full menu interface is activated using whatever
entries were found in the file. If you choose the <em class="dfn">command-line</em> menu
option, or if the configuration file was not found, then GRUB drops to
the command-line interface.
</p>

<ul class="mini-toc">
<li><a href="#Command_002dline-interface" accesskey="1">The flexible command-line interface</a></li>
<li><a href="#Menu-interface" accesskey="2">The simple menu interface</a></li>
<li><a href="#Menu-entry-editor" accesskey="3">Editing a menu entry</a></li>
</ul>
<hr>
<div class="section-level-extent" id="Command_002dline-interface">
<div class="nav-panel">
<p>
Next: <a href="#Menu-interface" accesskey="n" rel="next">The simple menu interface</a>, Up: <a href="#Interface" accesskey="u" rel="up">GRUB&rsquo;s user interface</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="The-flexible-command_002dline-interface"><span>14.1 The flexible command-line interface<a class="copiable-link" href="#The-flexible-command_002dline-interface"> &para;</a></span></h3>

<p>The command-line interface provides a prompt and after it an editable
text area much like a command-line in Unix or DOS. Each command is
immediately executed after it is entered<a class="footnote" id="DOCF8" href="#FOOT8"><sup>8</sup></a>. The commands (see <a class="pxref" href="#Commands">Available commands</a>) are a subset of those available
in the configuration file, used with exactly the same syntax.
</p>
<p>Cursor movement and editing of the text on the line can be done via a
subset of the functions available in the Bash shell:
</p>
<dl class="table">
<dt><kbd class="key">C-f</kbd></dt>
<dt><kbd class="key">PC right key</kbd></dt>
<dd><p>Move forward one character.
</p>
</dd>
<dt><kbd class="key">C-b</kbd></dt>
<dt><kbd class="key">PC left key</kbd></dt>
<dd><p>Move back one character.
</p>
</dd>
<dt><kbd class="key">C-a</kbd></dt>
<dt><kbd class="key">HOME</kbd></dt>
<dd><p>Move to the start of the line.
</p>
</dd>
<dt><kbd class="key">C-e</kbd></dt>
<dt><kbd class="key">END</kbd></dt>
<dd><p>Move the the end of the line.
</p>
</dd>
<dt><kbd class="key">C-d</kbd></dt>
<dt><kbd class="key">DEL</kbd></dt>
<dd><p>Delete the character underneath the cursor.
</p>
</dd>
<dt><kbd class="key">C-h</kbd></dt>
<dt><kbd class="key">BS</kbd></dt>
<dd><p>Delete the character to the left of the cursor.
</p>
</dd>
<dt><kbd class="key">C-k</kbd></dt>
<dd><p>Kill the text from the current cursor position to the end of the line.
</p>
</dd>
<dt><kbd class="key">C-u</kbd></dt>
<dd><p>Kill backward from the cursor to the beginning of the line.
</p>
</dd>
<dt><kbd class="key">C-y</kbd></dt>
<dd><p>Yank the killed text back into the buffer at the cursor.
</p>
</dd>
<dt><kbd class="key">C-p</kbd></dt>
<dt><kbd class="key">PC up key</kbd></dt>
<dd><p>Move up through the history list.
</p>
</dd>
<dt><kbd class="key">C-n</kbd></dt>
<dt><kbd class="key">PC down key</kbd></dt>
<dd><p>Move down through the history list.
</p></dd>
</dl>

<p>When typing commands interactively, if the cursor is within or before
the first word in the command-line, pressing the <kbd class="key">TAB</kbd> key (or
<kbd class="key">C-i</kbd>) will display a listing of the available commands, and if the
cursor is after the first word, the <kbd class="kbd"><kbd class="key">TAB</kbd></kbd> will provide a
completion listing of disks, partitions, and file names depending on the
context. Note that to obtain a list of drives, one must open a
parenthesis, as <code class="command">root (</code>.
</p>
<p>Note that you cannot use the completion functionality in the TFTP
filesystem. This is because TFTP doesn&rsquo;t support file name listing for
the security.
</p>

<hr>
</div>
<div class="section-level-extent" id="Menu-interface">
<div class="nav-panel">
<p>
Next: <a href="#Menu-entry-editor" accesskey="n" rel="next">Editing a menu entry</a>, Previous: <a href="#Command_002dline-interface" accesskey="p" rel="prev">The flexible command-line interface</a>, Up: <a href="#Interface" accesskey="u" rel="up">GRUB&rsquo;s user interface</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="The-simple-menu-interface"><span>14.2 The simple menu interface<a class="copiable-link" href="#The-simple-menu-interface"> &para;</a></span></h3>

<p>The menu interface is quite easy to use. Its commands are both
reasonably intuitive and described on screen.
</p>
<p>Basically, the menu interface provides a list of <em class="dfn">boot entries</em> to
the user to choose from. Use the arrow keys to select the entry of
choice, then press <kbd class="key">RET</kbd> to run it.  An optional timeout is
available to boot the default entry (the first one if not set), which is
aborted by pressing any key.
</p>
<p>Commands are available to enter a bare command-line by pressing <kbd class="key">c</kbd>
(which operates exactly like the non-config-file version of GRUB, but
allows one to return to the menu if desired by pressing <kbd class="key">ESC</kbd>) or to
edit any of the <em class="dfn">boot entries</em> by pressing <kbd class="key">e</kbd>.
</p>
<p>If you protect the menu interface with a password (see <a class="pxref" href="#Security">Security</a>),
all you can do is choose an entry by pressing <kbd class="key">RET</kbd>, or press
<kbd class="key">p</kbd> to enter the password.
</p>
<p>Pressing <kbd class="key">Ctrl-l</kbd> will refresh the menu, which can be useful when
connecting via serial after the menu has been drawn.
</p>

<hr>
</div>
<div class="section-level-extent" id="Menu-entry-editor">
<div class="nav-panel">
<p>
Previous: <a href="#Menu-interface" accesskey="p" rel="prev">The simple menu interface</a>, Up: <a href="#Interface" accesskey="u" rel="up">GRUB&rsquo;s user interface</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Editing-a-menu-entry"><span>14.3 Editing a menu entry<a class="copiable-link" href="#Editing-a-menu-entry"> &para;</a></span></h3>

<p>The menu entry editor looks much like the main menu interface, but the
lines in the menu are individual commands in the selected entry instead
of entry names.
</p>
<p>If an <kbd class="key">ESC</kbd> is pressed in the editor, it aborts all the changes made
to the configuration entry and returns to the main menu interface.
</p>
<p>Each line in the menu entry can be edited freely, and you can add new lines
by pressing <kbd class="key">RET</kbd> at the end of a line.  To boot the edited entry, press
<kbd class="key">Ctrl-x</kbd>.
</p>
<p>Although GRUB unfortunately does not support <em class="dfn">undo</em>, you can do almost
the same thing by just returning to the main menu using <kbd class="key">ESC</kbd>.
</p>

<hr>
</div>
</div>
<div class="chapter-level-extent" id="Environment">
<div class="nav-panel">
<p>
Next: <a href="#Modules" accesskey="n" rel="next">Modules</a>, Previous: <a href="#Interface" accesskey="p" rel="prev">GRUB&rsquo;s user interface</a>, Up: <a href="#Top" accesskey="u" rel="up">GNU GRUB manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h2 class="chapter" id="GRUB-environment-variables"><span>15 GRUB environment variables<a class="copiable-link" href="#GRUB-environment-variables"> &para;</a></span></h2>

<p>GRUB supports environment variables which are rather like those offered by
all Unix-like systems.  Environment variables have a name, which is unique
and is usually a short identifier, and a value, which is an arbitrary string
of characters.  They may be set (see <a class="pxref" href="#set">set</a>), unset (see <a class="pxref" href="#unset">unset</a>), or
looked up (see <a class="pxref" href="#Shell_002dlike-scripting">Writing full configuration files directly</a>) by name.
</p>
<p>A number of environment variables have special meanings to various parts of
GRUB.  Others may be used freely in GRUB configuration files.
</p>

<ul class="mini-toc">
<li><a href="#Special-environment-variables" accesskey="1">Special environment variables</a></li>
<li><a href="#Environment-block" accesskey="2">The GRUB environment block</a></li>
</ul>
<hr>
<div class="section-level-extent" id="Special-environment-variables">
<div class="nav-panel">
<p>
Next: <a href="#Environment-block" accesskey="n" rel="next">The GRUB environment block</a>, Up: <a href="#Environment" accesskey="u" rel="up">GRUB environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h3 class="section" id="Special-environment-variables-1"><span>15.1 Special environment variables<a class="copiable-link" href="#Special-environment-variables-1"> &para;</a></span></h3>

<p>These variables have special meaning to GRUB.
</p>

<ul class="mini-toc">
<li><a href="#appendedsig_005fkey_005fmgmt" accesskey="1">appendedsig_key_mgmt</a></li>
<li><a href="#biosnum" accesskey="2">biosnum</a></li>
<li><a href="#blsuki_005fsave_005fdefault" accesskey="3">blsuki_save_default</a></li>
<li><a href="#check_005fappended_005fsignatures" accesskey="4">check_appended_signatures</a></li>
<li><a href="#check_005fsignatures" accesskey="5">check_signatures</a></li>
<li><a href="#chosen" accesskey="6">chosen</a></li>
<li><a href="#cmdpath" accesskey="7">cmdpath</a></li>
<li><a href="#color_005fhighlight" accesskey="8">color_highlight</a></li>
<li><a href="#color_005fnormal" accesskey="9">color_normal</a></li>
<li><a href="#config_005fdirectory">config_directory</a></li>
<li><a href="#config_005ffile">config_file</a></li>
<li><a href="#debug">debug</a></li>
<li><a href="#default">default</a></li>
<li><a href="#fallback">fallback</a></li>
<li><a href="#gfxmode">gfxmode</a></li>
<li><a href="#gfxpayload">gfxpayload</a></li>
<li><a href="#gfxterm_005ffont">gfxterm_font</a></li>
<li><a href="#grub_005fcpu">grub_cpu</a></li>
<li><a href="#grub_005fplatform">grub_platform</a></li>
<li><a href="#icondir">icondir</a></li>
<li><a href="#lang">lang</a></li>
<li><a href="#locale_005fdir">locale_dir</a></li>
<li><a href="#lockdown">lockdown</a></li>
<li><a href="#menu_005fcolor_005fhighlight">menu_color_highlight</a></li>
<li><a href="#menu_005fcolor_005fnormal">menu_color_normal</a></li>
<li><a href="#net_005f_003cinterface_003e_005fboot_005ffile">net_<var class="var">&lt;interface&gt;</var>_boot_file</a></li>
<li><a href="#net_005f_003cinterface_003e_005fclientid">net_<var class="var">&lt;interface&gt;</var>_clientid</a></li>
<li><a href="#net_005f_003cinterface_003e_005fclientuuid">net_<var class="var">&lt;interface&gt;</var>_clientuuid</a></li>
<li><a href="#net_005f_003cinterface_003e_005fdhcp_005fserver_005fname">net_<var class="var">&lt;interface&gt;</var>_dhcp_server_name</a></li>
<li><a href="#net_005f_003cinterface_003e_005fdomain">net_<var class="var">&lt;interface&gt;</var>_domain</a></li>
<li><a href="#net_005f_003cinterface_003e_005fextensionspath">net_<var class="var">&lt;interface&gt;</var>_extensionspath</a></li>
<li><a href="#net_005f_003cinterface_003e_005fhostname">net_<var class="var">&lt;interface&gt;</var>_hostname</a></li>
<li><a href="#net_005f_003cinterface_003e_005fip">net_<var class="var">&lt;interface&gt;</var>_ip</a></li>
<li><a href="#net_005f_003cinterface_003e_005fmac">net_<var class="var">&lt;interface&gt;</var>_mac</a></li>
<li><a href="#net_005f_003cinterface_003e_005fnext_005fserver">net_<var class="var">&lt;interface&gt;</var>_next_server</a></li>
<li><a href="#net_005f_003cinterface_003e_005frootpath">net_<var class="var">&lt;interface&gt;</var>_rootpath</a></li>
<li><a href="#net_005fdefault_005finterface">net_default_interface</a></li>
<li><a href="#net_005fdefault_005fip">net_default_ip</a></li>
<li><a href="#net_005fdefault_005fmac">net_default_mac</a></li>
<li><a href="#net_005fdefault_005fserver">net_default_server</a></li>
<li><a href="#pager">pager</a></li>
<li><a href="#prefix">prefix</a></li>
<li><a href="#pxe_005fblksize">pxe_blksize</a></li>
<li><a href="#pxe_005fdefault_005fgateway">pxe_default_gateway</a></li>
<li><a href="#pxe_005fdefault_005fserver">pxe_default_server</a></li>
<li><a href="#root">root</a></li>
<li><a href="#shim_005flock">shim_lock</a></li>
<li><a href="#superusers">superusers</a></li>
<li><a href="#theme">theme</a></li>
<li><a href="#timeout">timeout</a></li>
<li><a href="#timeout_005fstyle">timeout_style</a></li>
<li><a href="#tpm_005ffail_005ffatal">tpm_fail_fatal</a></li>
</ul>
<hr>
<div class="subsection-level-extent" id="appendedsig_005fkey_005fmgmt">
<div class="nav-panel">
<p>
Next: <a href="#biosnum" accesskey="n" rel="next">biosnum</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="appendedsig_005fkey_005fmgmt-1"><span>15.1.1 appendedsig_key_mgmt<a class="copiable-link" href="#appendedsig_005fkey_005fmgmt-1"> &para;</a></span></h4>

<p>This variable controls whether GRUB enforces appended signature validation
using either <code class="code">static</code> or <code class="code">dynamic</code> key management. It is automatically
set by GRUB to either <code class="code">static</code> or <code class="code">dynamic</code> based on the
<strong class="strong">&rsquo;ibm,secure-boot&rsquo;</strong> device tree property and Platform KeyStore (PKS).
Also, it can be explicitly set to either <code class="code">static</code> or <code class="code">dynamic</code> by
setting the <code class="code">appendedsig_key_mgmt</code> variable from the GRUB console
when the GRUB is not locked down.
</p>
<p>See <a class="xref" href="#Using-appended-signatures">Using appended signatures in GRUB</a> for more information.
</p>
<hr>
</div>
<div class="subsection-level-extent" id="biosnum">
<div class="nav-panel">
<p>
Next: <a href="#blsuki_005fsave_005fdefault" accesskey="n" rel="next">blsuki_save_default</a>, Previous: <a href="#appendedsig_005fkey_005fmgmt" accesskey="p" rel="prev">appendedsig_key_mgmt</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="biosnum-1"><span>15.1.2 biosnum<a class="copiable-link" href="#biosnum-1"> &para;</a></span></h4>

<p>When chain-loading another boot loader (see <a class="pxref" href="#Chain_002dloading">Chain-loading an OS</a>), GRUB may
need to know what BIOS drive number corresponds to the root device
(see <a class="pxref" href="#root">root</a>) so that it can set up registers properly.  If the
<var class="var">biosnum</var> variable is set, it overrides GRUB&rsquo;s own means of guessing
this.
</p>
<p>For an alternative approach which also changes BIOS drive mappings for the
chain-loaded system, see <a class="pxref" href="#drivemap">drivemap</a>.
</p>
<hr>
</div>
<div class="subsection-level-extent" id="blsuki_005fsave_005fdefault">
<div class="nav-panel">
<p>
Next: <a href="#check_005fappended_005fsignatures" accesskey="n" rel="next">check_appended_signatures</a>, Previous: <a href="#biosnum" accesskey="p" rel="prev">biosnum</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="blsuki_005fsave_005fdefault-1"><span>15.1.3 blsuki_save_default<a class="copiable-link" href="#blsuki_005fsave_005fdefault-1"> &para;</a></span></h4>

<p>If this variable is set, menu entries generated from BLS config files
(see <a class="pxref" href="#blscfg">blscfg</a>) or UKI files (see <a class="pxref" href="#uki">uki</a>) will be set as the default boot
entry when selected.
</p>
<hr>
</div>
<div class="subsection-level-extent" id="check_005fappended_005fsignatures">
<div class="nav-panel">
<p>
Next: <a href="#check_005fsignatures" accesskey="n" rel="next">check_signatures</a>, Previous: <a href="#blsuki_005fsave_005fdefault" accesskey="p" rel="prev">blsuki_save_default</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="check_005fappended_005fsignatures-1"><span>15.1.4 check_appended_signatures<a class="copiable-link" href="#check_005fappended_005fsignatures-1"> &para;</a></span></h4>

<p>This variable controls whether GRUB enforces appended signature validation on
loaded kernel and GRUB module files. It is automatically set by GRUB
to either <code class="code">no</code> or <code class="code">yes</code> based on the <strong class="strong">&rsquo;ibm,secure-boot&rsquo;</strong> device
tree property. Also, it can be explicitly set to either <code class="code">no</code> or <code class="code">yes</code> by
setting the <code class="code">check_appended_signatures</code> variable from the GRUB console
when the GRUB is not locked down.
</p>
<p>See <a class="xref" href="#Using-appended-signatures">Using appended signatures in GRUB</a> for more information.
</p>
<hr>
</div>
<div class="subsection-level-extent" id="check_005fsignatures">
<div class="nav-panel">
<p>
Next: <a href="#chosen" accesskey="n" rel="next">chosen</a>, Previous: <a href="#check_005fappended_005fsignatures" accesskey="p" rel="prev">check_appended_signatures</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="check_005fsignatures-1"><span>15.1.5 check_signatures<a class="copiable-link" href="#check_005fsignatures-1"> &para;</a></span></h4>

<p>This variable controls whether GRUB enforces GPG-style digital signature
validation on loaded files. See <a class="xref" href="#Using-GPG_002dstyle-digital-signatures">Using GPG-style digital signatures in GRUB</a>.
</p>
<hr>
</div>
<div class="subsection-level-extent" id="chosen">
<div class="nav-panel">
<p>
Next: <a href="#cmdpath" accesskey="n" rel="next">cmdpath</a>, Previous: <a href="#check_005fsignatures" accesskey="p" rel="prev">check_signatures</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="chosen-1"><span>15.1.6 chosen<a class="copiable-link" href="#chosen-1"> &para;</a></span></h4>

<p>When executing a menu entry, GRUB sets the <var class="var">chosen</var> variable to the
title of the entry being executed.
</p>
<p>If the menu entry is in one or more submenus, then <var class="var">chosen</var> is set to
the titles of each of the submenus starting from the top level followed by
the title of the menu entry itself, separated by &lsquo;<samp class="samp">&gt;</samp>&rsquo;.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="cmdpath">
<div class="nav-panel">
<p>
Next: <a href="#color_005fhighlight" accesskey="n" rel="next">color_highlight</a>, Previous: <a href="#chosen" accesskey="p" rel="prev">chosen</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="cmdpath-1"><span>15.1.7 cmdpath<a class="copiable-link" href="#cmdpath-1"> &para;</a></span></h4>

<p>The location from which <samp class="file">core.img</samp> was loaded as an absolute
directory name (see <a class="pxref" href="#File-name-syntax">How to specify files</a>).  This is set by GRUB at
startup based on information returned by platform firmware.  Not every
platform provides this information and some may return only device
without path name.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="color_005fhighlight">
<div class="nav-panel">
<p>
Next: <a href="#color_005fnormal" accesskey="n" rel="next">color_normal</a>, Previous: <a href="#cmdpath" accesskey="p" rel="prev">cmdpath</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="color_005fhighlight-1"><span>15.1.8 color_highlight<a class="copiable-link" href="#color_005fhighlight-1"> &para;</a></span></h4>

<p>This variable contains the &ldquo;highlight&rdquo; foreground and background terminal
colors, separated by a slash (&lsquo;<samp class="samp">/</samp>&rsquo;).  Setting this variable changes
those colors.  For the available color names, see <a class="pxref" href="#color_005fnormal">color_normal</a>.
</p>
<p>The default is &lsquo;<samp class="samp">black/light-gray</samp>&rsquo;.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="color_005fnormal">
<div class="nav-panel">
<p>
Next: <a href="#config_005fdirectory" accesskey="n" rel="next">config_directory</a>, Previous: <a href="#color_005fhighlight" accesskey="p" rel="prev">color_highlight</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="color_005fnormal-1"><span>15.1.9 color_normal<a class="copiable-link" href="#color_005fnormal-1"> &para;</a></span></h4>

<p>This variable contains the &ldquo;normal&rdquo; foreground and background terminal
colors, separated by a slash (&lsquo;<samp class="samp">/</samp>&rsquo;).  Setting this variable changes
those colors.  Each color must be a name from the following list:
</p>
<ul class="itemize mark-bullet">
<li>black
</li><li>blue
</li><li>green
</li><li>cyan
</li><li>red
</li><li>magenta
</li><li>brown
</li><li>light-gray
</li><li>dark-gray
</li><li>light-blue
</li><li>light-green
</li><li>light-cyan
</li><li>light-red
</li><li>light-magenta
</li><li>yellow
</li><li>white
</li></ul>

<p>The default is &lsquo;<samp class="samp">light-gray/black</samp>&rsquo;.
</p>
<p>The color support support varies from terminal to terminal.
</p>
<p>&lsquo;<samp class="samp">morse</samp>&rsquo; has no color support at all.
</p>
<p>&lsquo;<samp class="samp">mda_text</samp>&rsquo; color support is limited to highlighting by
black/white reversal.
</p>
<p>&lsquo;<samp class="samp">console</samp>&rsquo; on ARC, EMU and IEEE1275, &lsquo;<samp class="samp">serial_*</samp>&rsquo; and
&lsquo;<samp class="samp">spkmodem</samp>&rsquo; are governed by terminfo and support
only 8 colors if in modes &lsquo;<samp class="samp">vt100-color</samp>&rsquo; (default for console on emu),
&lsquo;<samp class="samp">arc</samp>&rsquo; (default for console on ARC), &lsquo;<samp class="samp">ieee1275</samp>&rsquo; (default
for console on IEEE1275). When in mode &lsquo;<samp class="samp">vt100</samp>&rsquo;
then the color support is limited to highlighting by black/white
reversal. When in mode &lsquo;<samp class="samp">dumb</samp>&rsquo; there is no color support.
</p>
<p>When console supports no colors this setting is ignored.
When console supports 8 colors, then the colors from the
second half of the previous list are mapped to the
matching colors of first half.
</p>
<p>&lsquo;<samp class="samp">console</samp>&rsquo; on EFI and BIOS and &lsquo;<samp class="samp">vga_text</samp>&rsquo; support all 16 colors.
</p>
<p>&lsquo;<samp class="samp">gfxterm</samp>&rsquo; supports all 16 colors and would be theoretically extendable
to support whole rgb24 palette but currently there is no compelling reason
to go beyond the current 16 colors.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="config_005fdirectory">
<div class="nav-panel">
<p>
Next: <a href="#config_005ffile" accesskey="n" rel="next">config_file</a>, Previous: <a href="#color_005fnormal" accesskey="p" rel="prev">color_normal</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="config_005fdirectory-1"><span>15.1.10 config_directory<a class="copiable-link" href="#config_005fdirectory-1"> &para;</a></span></h4>

<p>This variable is automatically set by GRUB to the directory part of
current configuration file name (see <a class="pxref" href="#config_005ffile">config_file</a>).
</p>

<hr>
</div>
<div class="subsection-level-extent" id="config_005ffile">
<div class="nav-panel">
<p>
Next: <a href="#debug" accesskey="n" rel="next">debug</a>, Previous: <a href="#config_005fdirectory" accesskey="p" rel="prev">config_directory</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="config_005ffile-1"><span>15.1.11 config_file<a class="copiable-link" href="#config_005ffile-1"> &para;</a></span></h4>

<p>This variable is automatically set by GRUB to the name of configuration file that is being
processed by commands <code class="command">configfile</code> (see <a class="pxref" href="#configfile">configfile</a>) or <code class="command">normal</code>
(see <a class="pxref" href="#normal">normal</a>).  It is restored to the previous value when command completes.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="debug">
<div class="nav-panel">
<p>
Next: <a href="#default" accesskey="n" rel="next">default</a>, Previous: <a href="#config_005ffile" accesskey="p" rel="prev">config_file</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="debug-1"><span>15.1.12 debug<a class="copiable-link" href="#debug-1"> &para;</a></span></h4>

<p>This variable may be set to enable debugging output from various components
of GRUB. The value is an ordered list of debug facility names separated by
whitespace or &lsquo;<samp class="samp">,</samp>&rsquo;. If the special facility named &lsquo;<samp class="samp">all</samp>&rsquo; is present
then debugging output of all facility names is enabled at the start of
processing the value of this variable. A facility&rsquo;s debug output can then be
disabled by prefixing its name with a &lsquo;<samp class="samp">-</samp>&rsquo;. The last occurence facility
name with or without a leading &lsquo;<samp class="samp">-</samp>&rsquo; takes precendent over any previous
occurence. This allows the easy enabling or disabling of facilities by
appending a &lsquo;<samp class="samp">,</samp>&rsquo; and then the facility name with or without the leading
&lsquo;<samp class="samp">-</samp>&rsquo;, which will preserve the state of the rest of the facilities.
The facility names are the first argument to grub_dprintf. Consult the
source for more details.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="default">
<div class="nav-panel">
<p>
Next: <a href="#fallback" accesskey="n" rel="next">fallback</a>, Previous: <a href="#debug" accesskey="p" rel="prev">debug</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="default-1"><span>15.1.13 default<a class="copiable-link" href="#default-1"> &para;</a></span></h4>

<p>If this variable is set, it identifies a menu entry that should be
selected by default, possibly after a timeout (see <a class="pxref" href="#timeout">timeout</a>).  The
entry may be identified by number (starting from 0 at each level of
the hierarchy), by title, or by id.
</p>
<p>For example, if you have:
</p>
<pre class="verbatim">menuentry 'Example GNU/Linux distribution' --class gnu-linux --id example-gnu-linux {
	...
}
</pre>
<p>then you can make this the default using:
</p>
<div class="example">
<pre class="example-preformatted">default=example-gnu-linux
</pre></div>

<p>If the entry is in a submenu, then it must be identified using the
number, title, or id of each of the submenus starting from the top
level, followed by the number, title, or id of the menu entry itself,
with each element separated by &lsquo;<samp class="samp">&gt;</samp>&rsquo;.  For example, take the
following menu structure:
</p>
<div class="example">
<pre class="example-preformatted">GNU/Hurd --id gnu-hurd
  Standard Boot --id=gnu-hurd-std
  Rescue shell --id=gnu-hurd-rescue
Other platforms --id=other
  Minix --id=minix
    Version 3.4.0 --id=minix-3.4.0
    Version 3.3.0 --id=minix-3.3.0
  GRUB Invaders --id=grub-invaders
</pre></div>

<p>The more recent release of Minix would then be identified as
&lsquo;<samp class="samp">Other platforms&gt;Minix&gt;Version 3.4.0</samp>&rsquo;, or as &lsquo;<samp class="samp">1&gt;0&gt;0</samp>&rsquo;, or as
&lsquo;<samp class="samp">other&gt;minix&gt;minix-3.4.0</samp>&rsquo;.
</p>
<p>This variable is often set by &lsquo;<samp class="samp">GRUB_DEFAULT</samp>&rsquo; (see <a class="pxref" href="#Simple-configuration">Simple configuration handling</a>), <code class="command">grub2-set-default</code>, or <code class="command">grub2-reboot</code>.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="fallback">
<div class="nav-panel">
<p>
Next: <a href="#gfxmode" accesskey="n" rel="next">gfxmode</a>, Previous: <a href="#default" accesskey="p" rel="prev">default</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="fallback-1"><span>15.1.14 fallback<a class="copiable-link" href="#fallback-1"> &para;</a></span></h4>

<p>If this variable is set, it identifies a menu entry that should be selected
if the default menu entry fails to boot.  Entries are identified in the same
way as for &lsquo;<samp class="samp">default</samp>&rsquo; (see <a class="pxref" href="#default">default</a>).
</p>

<hr>
</div>
<div class="subsection-level-extent" id="gfxmode">
<div class="nav-panel">
<p>
Next: <a href="#gfxpayload" accesskey="n" rel="next">gfxpayload</a>, Previous: <a href="#fallback" accesskey="p" rel="prev">fallback</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="gfxmode-1"><span>15.1.15 gfxmode<a class="copiable-link" href="#gfxmode-1"> &para;</a></span></h4>

<p>If this variable is set, it sets the resolution used on the &lsquo;<samp class="samp">gfxterm</samp>&rsquo;
graphical terminal.  Note that you can only use modes which your graphics
card supports via VESA BIOS Extensions (VBE), so for example native LCD
panel resolutions may not be available.  The default is &lsquo;<samp class="samp">auto</samp>&rsquo;, which
selects a platform-specific default that should look reasonable. Supported
modes can be listed by &lsquo;<samp class="samp">videoinfo</samp>&rsquo; command in GRUB.
</p>
<p>The resolution may be specified as a sequence of one or more modes,
separated by commas (&lsquo;<samp class="samp">,</samp>&rsquo;) or semicolons (&lsquo;<samp class="samp">;</samp>&rsquo;); each will be tried
in turn until one is found.  Each mode should be either &lsquo;<samp class="samp">auto</samp>&rsquo;,
&lsquo;<samp class="samp"><var class="var">width</var>x<var class="var">height</var></samp>&rsquo;, or
&lsquo;<samp class="samp"><var class="var">width</var>x<var class="var">height</var>x<var class="var">depth</var></samp>&rsquo;.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="gfxpayload">
<div class="nav-panel">
<p>
Next: <a href="#gfxterm_005ffont" accesskey="n" rel="next">gfxterm_font</a>, Previous: <a href="#gfxmode" accesskey="p" rel="prev">gfxmode</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="gfxpayload-1"><span>15.1.16 gfxpayload<a class="copiable-link" href="#gfxpayload-1"> &para;</a></span></h4>

<p>If this variable is set, it controls the video mode in which the Linux
kernel starts up, replacing the &lsquo;<samp class="samp">vga=</samp>&rsquo; boot option (see <a class="pxref" href="#linux">linux</a>).  It
may be set to &lsquo;<samp class="samp">text</samp>&rsquo; to force the Linux kernel to boot in normal text
mode, &lsquo;<samp class="samp">keep</samp>&rsquo; to preserve the graphics mode set using &lsquo;<samp class="samp">gfxmode</samp>&rsquo;, or
any of the permitted values for &lsquo;<samp class="samp">gfxmode</samp>&rsquo; to set a particular graphics
mode (see <a class="pxref" href="#gfxmode">gfxmode</a>).
</p>
<p>Depending on your kernel, your distribution, your graphics card, and the
phase of the moon, note that using this option may cause GNU/Linux to suffer
from various display problems, particularly during the early part of the
boot sequence.  If you have problems, set this variable to &lsquo;<samp class="samp">text</samp>&rsquo; and
GRUB will tell Linux to boot in normal text mode.
</p>
<p>The default is platform-specific.  On platforms with a native text mode
(such as PC BIOS platforms), the default is &lsquo;<samp class="samp">text</samp>&rsquo;.  Otherwise the
default may be &lsquo;<samp class="samp">auto</samp>&rsquo; or a specific video mode.
</p>
<p>This variable is often set by &lsquo;<samp class="samp">GRUB_GFXPAYLOAD_LINUX</samp>&rsquo; (see <a class="pxref" href="#Simple-configuration">Simple configuration handling</a>).
</p>

<hr>
</div>
<div class="subsection-level-extent" id="gfxterm_005ffont">
<div class="nav-panel">
<p>
Next: <a href="#grub_005fcpu" accesskey="n" rel="next">grub_cpu</a>, Previous: <a href="#gfxpayload" accesskey="p" rel="prev">gfxpayload</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="gfxterm_005ffont-1"><span>15.1.17 gfxterm_font<a class="copiable-link" href="#gfxterm_005ffont-1"> &para;</a></span></h4>

<p>If this variable is set, it names a font to use for text on the
&lsquo;<samp class="samp">gfxterm</samp>&rsquo; graphical terminal.  Otherwise, &lsquo;<samp class="samp">gfxterm</samp>&rsquo; may use any
available font.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="grub_005fcpu">
<div class="nav-panel">
<p>
Next: <a href="#grub_005fplatform" accesskey="n" rel="next">grub_platform</a>, Previous: <a href="#gfxterm_005ffont" accesskey="p" rel="prev">gfxterm_font</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="grub_005fcpu-1"><span>15.1.18 grub_cpu<a class="copiable-link" href="#grub_005fcpu-1"> &para;</a></span></h4>

<p>In normal mode (see <a class="pxref" href="#normal">normal</a>), GRUB sets the &lsquo;<samp class="samp">grub_cpu</samp>&rsquo; variable to
the CPU type for which GRUB was built (e.g. &lsquo;<samp class="samp">i386</samp>&rsquo; or &lsquo;<samp class="samp">powerpc</samp>&rsquo;).
</p>

<hr>
</div>
<div class="subsection-level-extent" id="grub_005fplatform">
<div class="nav-panel">
<p>
Next: <a href="#icondir" accesskey="n" rel="next">icondir</a>, Previous: <a href="#grub_005fcpu" accesskey="p" rel="prev">grub_cpu</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="grub_005fplatform-1"><span>15.1.19 grub_platform<a class="copiable-link" href="#grub_005fplatform-1"> &para;</a></span></h4>

<p>In normal mode (see <a class="pxref" href="#normal">normal</a>), GRUB sets the &lsquo;<samp class="samp">grub_platform</samp>&rsquo; variable
to the platform for which GRUB was built (e.g. &lsquo;<samp class="samp">pc</samp>&rsquo; or &lsquo;<samp class="samp">efi</samp>&rsquo;).
</p>

<hr>
</div>
<div class="subsection-level-extent" id="icondir">
<div class="nav-panel">
<p>
Next: <a href="#lang" accesskey="n" rel="next">lang</a>, Previous: <a href="#grub_005fplatform" accesskey="p" rel="prev">grub_platform</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="icondir-1"><span>15.1.20 icondir<a class="copiable-link" href="#icondir-1"> &para;</a></span></h4>

<p>If this variable is set, it names a directory in which the GRUB graphical
menu should look for icons after looking in the theme&rsquo;s &lsquo;<samp class="samp">icons</samp>&rsquo;
directory.  See <a class="xref" href="#Theme-file-format">Theme file format</a>.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="lang">
<div class="nav-panel">
<p>
Next: <a href="#locale_005fdir" accesskey="n" rel="next">locale_dir</a>, Previous: <a href="#icondir" accesskey="p" rel="prev">icondir</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="lang-1"><span>15.1.21 lang<a class="copiable-link" href="#lang-1"> &para;</a></span></h4>

<p>If this variable is set, it names the language code that the
<code class="command">gettext</code> command (see <a class="pxref" href="#gettext">gettext</a>) uses to translate strings.  For
example, French would be named as &lsquo;<samp class="samp">fr</samp>&rsquo;, and Simplified Chinese as
&lsquo;<samp class="samp">zh_CN</samp>&rsquo;.
</p>
<p><code class="command">grub2-mkconfig</code> (see <a class="pxref" href="#Simple-configuration">Simple configuration handling</a>) will try to set a
reasonable default for this variable based on the system locale.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="locale_005fdir">
<div class="nav-panel">
<p>
Next: <a href="#lockdown" accesskey="n" rel="next">lockdown</a>, Previous: <a href="#lang" accesskey="p" rel="prev">lang</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="locale_005fdir-1"><span>15.1.22 locale_dir<a class="copiable-link" href="#locale_005fdir-1"> &para;</a></span></h4>

<p>If this variable is set, it names the directory where translation files may
be found (see <a class="pxref" href="#gettext">gettext</a>), usually <samp class="file">/boot/grub2/locale</samp>.  Otherwise,
internationalization is disabled.
</p>
<p><code class="command">grub2-mkconfig</code> (see <a class="pxref" href="#Simple-configuration">Simple configuration handling</a>) will set a reasonable
default for this variable if internationalization is needed and any
translation files are available.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="lockdown">
<div class="nav-panel">
<p>
Next: <a href="#menu_005fcolor_005fhighlight" accesskey="n" rel="next">menu_color_highlight</a>, Previous: <a href="#locale_005fdir" accesskey="p" rel="prev">locale_dir</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="lockdown-1"><span>15.1.23 lockdown<a class="copiable-link" href="#lockdown-1"> &para;</a></span></h4>

<p>If this variable is set to &lsquo;<samp class="samp">y</samp>&rsquo;, it means that GRUB has entered
see <a class="pxref" href="#Lockdown">Lockdown when booting on a secure setup</a> mode.
</p>

<hr>
</div>
<div class="subsection-level-extent" id="menu_005fcolor_005fhighlight">
<div class="nav-panel">
<p>
Next: <a href="#menu_005fcolor_005fnormal" accesskey="n" rel="next">menu_color_normal</a>, Previous: <a href="#lockdown" accesskey="p" rel="prev">lockdown</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="menu_005fcolor_005fhighlight-1"><span>15.1.24 menu_color_highlight<a class="copiable-link" href="#menu_005fcolor_005fhighlight-1"> &para;</a></span></h4>

<p>This variable contains the foreground and background colors to be used for
the highlighted menu entry, separated by a slash (&lsquo;<samp class="samp">/</samp>&rsquo;).  Setting this
variable changes those colors.  For the available color names,
see <a class="pxref" href="#color_005fnormal">color_normal</a>.
</p>
<p>The default is the value of &lsquo;<samp class="samp">color_highlight</samp>&rsquo;
(see <a class="pxref" href="#color_005fhighlight">color_highlight</a>).
</p>

<hr>
</div>
<div class="subsection-level-extent" id="menu_005fcolor_005fnormal">
<div class="nav-panel">
<p>
Next: <a href="#net_005f_003cinterface_003e_005fboot_005ffile" accesskey="n" rel="next">net_<var class="var">&lt;interface&gt;</var>_boot_file</a>, Previous: <a href="#menu_005fcolor_005fhighlight" accesskey="p" rel="prev">menu_color_highlight</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="menu_005fcolor_005fnormal-1"><span>15.1.25 menu_color_normal<a class="copiable-link" href="#menu_005fcolor_005fnormal-1"> &para;</a></span></h4>

<p>This variable contains the foreground and background colors to be used for
non-highlighted menu entries, separated by a slash (&lsquo;<samp class="samp">/</samp>&rsquo;).  Setting this
variable changes those colors.  For the available color names,
see <a class="pxref" href="#color_005fnormal">color_normal</a>.
</p>
<p>The default is the value of &lsquo;<samp class="samp">color_normal</samp>&rsquo; (see <a class="pxref" href="#color_005fnormal">color_normal</a>).
</p>

<hr>
</div>
<div class="subsection-level-extent" id="net_005f_003cinterface_003e_005fboot_005ffile">
<div class="nav-panel">
<p>
Next: <a href="#net_005f_003cinterface_003e_005fclientid" accesskey="n" rel="next">net_<var class="var">&lt;interface&gt;</var>_clientid</a>, Previous: <a href="#menu_005fcolor_005fnormal" accesskey="p" rel="prev">menu_color_normal</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="subsection" id="net_005f_003cinterface_003e_005fboot_005ffile-1"><span>15.1.26 net_<var class="var">&lt;interface&gt;</var>_boot_file<a class="copiable-link" href="#net_005f_003cinterface_003e_005fboot_005ffile-1"> &para;</a></span></h4>