13 The list of available commands
*********************************

In this chapter, we list all commands that are available in GRUB.

   Commands belong to different groups. A few can only be used in the
global section of the configuration file (or "menu"); most of them can
be entered on the command-line and can be used either anywhere in the
menu or specifically in the menu entries.

13.1 The list of commands for the menu only
===========================================

The semantics used in parsing the configuration file are the following:

   * The menu-specific commands have to be used before any others.

   * The files _must_ be in plain-text format.

   * `#' at the beginning of a line in a configuration file means it is
     only a comment.

   * Options are separated by spaces.

   * All numbers can be either decimal or hexadecimal. A hexadecimal
     number must be preceded by `0x', and is case-insensitive.

   * Extra options or text at the end of the line are ignored unless
     otherwise specified.

   * Unrecognized commands are added to the current entry, except
     before entries start, where they are ignored.

   These commands can only be used in the menu:

13.1.1 default
--------------

 -- Command: default num
     Set the default entry to the entry number NUM. Numbering starts
     from 0, and the entry number 0 is the default if the command is not
     used.

     You can specify `saved' instead of a number. In this case, the
     default entry is the entry saved with the command `savedefault'.
     *Note savedefault::, for more information.

13.1.2 fallback
---------------

 -- Command: fallback num...
     Go into unattended boot mode: if the default boot entry has any
     errors, instead of waiting for the user to do something,
     immediately start over using the NUM entry (same numbering as the
     `default' command (*note default::)). This obviously won't help if
     the machine was rebooted by a kernel that GRUB loaded. You can
     specify multiple fallback entry numbers.

13.1.3 hiddenmenu
-----------------

 -- Command: hiddenmenu
     Don't display the menu. If the command is used, no menu will be
     displayed on the control terminal, and the default entry will be
     booted after the timeout expired. The user can still request the
     menu to be displayed by pressing <ESC> before the timeout expires.
     See also *Note Hidden menu interface::.

13.1.4 timeout
--------------

 -- Command: timeout sec
     Set a timeout, in SEC seconds, before automatically booting the
     default entry (normally the first entry defined).

13.1.5 title
------------

 -- Command: title name ...
     Start a new boot entry, and set its name to the contents of the
     rest of the line, starting with the first non-space character.

13.2 The list of general commands
=================================

Commands usable anywhere in the menu and in the command-line.

13.2.1 bootp
------------

 -- Command: bootp [`--with-configfile']
     Initialize a network device via the "BOOTP" protocol. This command
     is only available if GRUB is compiled with netboot support. See
     also *Note Network::.

     If you specify `--with-configfile' to this command, GRUB will
     fetch and load a configuration file specified by your BOOTP server
     with the vendor tag `150'.

13.2.2 color
------------

 -- Command: color normal [highlight]
     Change the menu colors. The color NORMAL is used for most lines in
     the menu (*note Menu interface::), and the color HIGHLIGHT is used
     to highlight the line where the cursor points. If you omit
     HIGHLIGHT, then the inverted color of NORMAL is used for the
     highlighted line. The format of a color is
     `FOREGROUND/BACKGROUND'. FOREGROUND and BACKGROUND are symbolic
     color names. A symbolic color name must be one of these:

        * black

        * blue

        * green

        * cyan

        * red

        * magenta

        * brown

        * light-gray

          *These below can be specified only for the foreground.*

        * dark-gray

        * light-blue

        * light-green

        * light-cyan

        * light-red

        * light-magenta

        * yellow

        * white

     But only the first eight names can be used for BACKGROUND. You can
     prefix `blink-' to FOREGROUND if you want a blinking foreground
     color.

     This command can be used in the configuration file and on the
     command line, so you may write something like this in your
     configuration file:

          # Set default colors.
          color light-gray/blue black/light-gray

          # Change the colors.
          title OS-BS like
          color magenta/blue black/magenta

13.2.3 device
-------------

 -- Command: device drive file
     In the grub shell, specify the file FILE as the actual drive for a
     BIOS drive DRIVE. You can use this command to create a disk image,
     and/or to fix the drives guessed by GRUB when GRUB fails to
     determine them correctly, like this:

          grub> device (fd0) /floppy-image
          grub> device (hd0) /dev/sd0

     This command can be used only in the grub shell (*note Invoking
     the grub shell::).

13.2.4 dhcp
-----------

 -- Command: dhcp [-with-configfile]
     Initialize a network device via the "DHCP" protocol. Currently,
     this command is just an alias for `bootp', since the two protocols
     are very similar. This command is only available if GRUB is
     compiled with netboot support. See also *Note Network::.

     If you specify `--with-configfile' to this command, GRUB will
     fetch and load a configuration file specified by your DHCP server
     with the vendor tag `150'.

13.2.5 hide
-----------

 -- Command: hide partition
     Hide the partition PARTITION by setting the "hidden" bit in its
     partition type code. This is useful only when booting DOS or
     Windows and multiple primary FAT partitions exist in one disk. See
     also *Note DOS/Windows::.

13.2.6 ifconfig
---------------

 -- Command: ifconfig [`--server=server'] [`--gateway=gateway']
          [`--mask=mask'] [`--address=address']
     Configure the IP address, the netmask, the gateway, and the server
     address of a network device manually. The values must be in dotted
     decimal format, like `192.168.11.178'. The order of the options is
     not important. This command shows current network configuration,
     if no option is specified. See also *Note Network::.

13.2.7 pager
------------

 -- Command: pager [flag]
     Toggle or set the state of the internal pager. If FLAG is `on',
     the internal pager is enabled. If FLAG is `off', it is disabled.
     If no argument is given, the state is toggled.

13.2.8 partnew
--------------

 -- Command: partnew part type from len
     Create a new primary partition. PART is a partition specification
     in GRUB syntax (*note Naming convention::); TYPE is the partition
     type and must be a number in the range `0-0xff'; FROM is the
     starting address and LEN is the length, both in sector units.

13.2.9 parttype
---------------

 -- Command: parttype part type
     Change the type of an existing partition.  PART is a partition
     specification in GRUB syntax (*note Naming convention::); TYPE is
     the new partition type and must be a number in the range 0-0xff.

13.2.10 password
----------------

 -- Command: password [`--md5'] passwd [new-config-file]
     If used in the first section of a menu file, disable all
     interactive editing control (menu entry editor and command-line)
     and entries protected by the command `lock'. If the password
     PASSWD is entered, it loads the NEW-CONFIG-FILE as a new config
     file and restarts the GRUB Stage 2, if NEW-CONFIG-FILE is
     specified. Otherwise, GRUB will just unlock the privileged
     instructions.  You can also use this command in the script
     section, in which case it will ask for the password, before
     continuing.  The option `--md5' tells GRUB that PASSWD is
     encrypted with `md5crypt' (*note md5crypt::).

13.2.11 rarp
------------

 -- Command: rarp
     Initialize a network device via the "RARP" protocol.  This command
     is only available if GRUB is compiled with netboot support. See
     also *Note Network::.

13.2.12 serial
--------------

 -- Command: serial [`--unit=unit'] [`--port=port'] [`--speed=speed']
          [`--word=word'] [`--parity=parity'] [`--stop=stop']
          [`--device=dev']
     Initialize a serial device. UNIT is a number in the range 0-3
     specifying which serial port to use; default is 0, which
     corresponds to the port often called COM1. PORT is the I/O port
     where the UART is to be found; if specified it takes precedence
     over UNIT.  SPEED is the transmission speed; default is 9600. WORD
     and STOP are the number of data bits and stop bits. Data bits must
     be in the range 5-8 and stop bits must be 1 or 2. Default is 8 data
     bits and one stop bit. PARITY is one of `no', `odd', `even' and
     defaults to `no'. The option `--device' can only be used in the
     grub shell and is used to specify the tty device to be used in the
     host operating system (*note Invoking the grub shell::).

     The serial port is not used as a communication channel unless the
     `terminal' command is used (*note terminal::).

     This command is only available if GRUB is compiled with serial
     support. See also *Note Serial terminal::.

13.2.13 setkey
--------------

 -- Command: setkey [to_key from_key]
     Change the keyboard map. The key FROM_KEY is mapped to the key
     TO_KEY. If no argument is specified, reset key mappings. Note that
     this command _does not_ exchange the keys. If you want to exchange
     the keys, run this command again with the arguments exchanged,
     like this:

          grub> setkey capslock control
          grub> setkey control capslock

     A key must be an alphabet letter, a digit, or one of these symbols:
     `escape', `exclam', `at', `numbersign', `dollar', `percent',
     `caret', `ampersand', `asterisk', `parenleft', `parenright',
     `minus', `underscore', `equal', `plus', `backspace', `tab',
     `bracketleft', `braceleft', `bracketright', `braceright', `enter',
     `control', `semicolon', `colon', `quote', `doublequote',
     `backquote', `tilde', `shift', `backslash', `bar', `comma',
     `less', `period', `greater', `slash', `question', `alt', `space',
     `capslock', `FX' (`X' is a digit), and `delete'. This table
     describes to which character each of the symbols corresponds:

    `exclam'
          `!'

    `at'
          `@'

    `numbersign'
          `#'

    `dollar'
          `$'

    `percent'
          `%'

    `caret'
          `^'

    `ampersand'
          `&'

    `asterisk'
          `*'

    `parenleft'
          `('

    `parenright'
          `)'

    `minus'
          `-'

    `underscore'
          `_'

    `equal'
          `='

    `plus'
          `+'

    `bracketleft'
          `['

    `braceleft'
          `{'

    `bracketright'
          `]'

    `braceright'
          `}'

    `semicolon'
          `;'

    `colon'
          `:'

    `quote'
          `''

    `doublequote'
          `"'

    `backquote'
          ``'

    `tilde'
          `~'

    `backslash'
          `\'

    `bar'
          `|'

    `comma'
          `,'

    `less'
          `<'

    `period'
          `.'

    `greater'
          `>'

    `slash'
          `/'

    `question'
          `?'

    `space'
          ` '

13.2.14 terminal
----------------

 -- Command: terminal [`--dumb'] [`--no-echo'] [`--no-edit']
          [`--timeout=secs'] [`--lines=lines'] [`--silent'] [`console']
          [`serial'] [`hercules']
     Select a terminal for user interaction. The terminal is assumed to
     be VT100-compatible unless `--dumb' is specified. If both
     `console' and `serial' are specified, then GRUB will use the one
     where a key is entered first or the first when the timeout
     expires. If neither are specified, the current setting is
     reported. This command is only available if GRUB is compiled with
     serial support. See also *Note Serial terminal::.

     This may not make sense for most users, but GRUB supports Hercules
     console as well. Hercules console is usable like the ordinary
     console, and the usage is quite similar to that for serial
     terminals: specify `hercules' as the argument.

     The option `--lines' defines the number of lines in your terminal,
     and it is used for the internal pager function. If you don't
     specify this option, the number is assumed as 24.

     The option `--silent' suppresses the message to prompt you to hit
     any key. This might be useful if your system has no terminal
     device.

     The option `--no-echo' has GRUB not to echo back input characters.
     This implies the option `--no-edit'.

     The option `--no-edit' disables the BASH-like editing feature.

13.2.15 terminfo
----------------

 -- Command: terminfo `--name=name' `--cursor-address=seq'
          [`--clear-screen=seq'] [`--enter-standout-mode=seq']
          [`--exit-standout-mode=seq']
     Define the capabilities of your terminal. Use this command to
     define escape sequences, if it is not vt100-compatible. You may
     use `\e' for <ESC> and `^X' for a control character.

     You can use the utility `grub-terminfo' to generate appropriate
     arguments to this command. *Note Invoking grub-terminfo::.

     If no option is specified, the current settings are printed.

13.2.16 tftpserver
------------------

 -- Command: tftpserver ipaddr
     *Caution:* This command exists only for backward compatibility.
     Use `ifconfig' (*note ifconfig::) instead.

     Override a TFTP server address returned by a BOOTP/DHCP/RARP
     server. The argument IPADDR must be in dotted decimal format, like
     `192.168.0.15'.  This command is only available if GRUB is compiled
     with netboot support. See also *Note Network::.

13.2.17 unhide
--------------

 -- Command: unhide partition
     Unhide the partition PARTITION by clearing the "hidden" bit in its
     partition type code. This is useful only when booting DOS or
     Windows and multiple primary partitions exist on one disk. See also
     *Note DOS/Windows::.

13.3 The list of command-line and menu entry commands
=====================================================

These commands are usable in the command-line and in menu entries.  If
you forget a command, you can run the command `help' (*note help::).

13.3.1 blocklist
----------------

 -- Command: blocklist file
     Print the block list notation of the file FILE. *Note Block list
     syntax::.

13.3.2 boot
-----------

 -- Command: boot
     Boot the OS or chain-loader which has been loaded. Only necessary
     if running the fully interactive command-line (it is implicit at
     the end of a menu entry).

13.3.3 cat
----------

 -- Command: cat file
     Display the contents of the file FILE. This command may be useful
     to remind you of your OS's root partition:

          grub> cat /etc/fstab

13.3.4 chainloader
------------------

 -- Command: chainloader [`--force'] file
     Load FILE as a chain-loader. Like any other file loaded by the
     filesystem code, it can use the blocklist notation to grab the
     first sector of the current partition with `+1'. If you specify the
     option `--force', then load FILE forcibly, whether it has a
     correct signature or not. This is required when you want to load a
     defective boot loader, such as SCO UnixWare 7.1 (*note SCO
     UnixWare::).

13.3.5 cmp
----------

 -- Command: cmp file1 file2
     Compare the file FILE1 with the file FILE2. If they differ in
     size, print the sizes like this:

          Differ in size: 0x1234 [foo], 0x4321 [bar]

     If the sizes are equal but the bytes at an offset differ, then
     print the bytes like this:

          Differ at the offset 777: 0xbe [foo], 0xef [bar]

     If they are completely identical, nothing will be printed.

13.3.6 configfile
-----------------

 -- Command: configfile file
     Load FILE as a configuration file.

13.3.7 debug
------------

 -- Command: debug
     Toggle debug mode (by default it is off). When debug mode is on,
     some extra messages are printed to show disk activity. This global
     debug flag is mainly useful for GRUB developers when testing new
     code.

13.3.8 displayapm
-----------------

 -- Command: displayapm
     Display APM BIOS information.

13.3.9 displaymem
-----------------

 -- Command: displaymem
     Display what GRUB thinks the system address space map of the
     machine is, including all regions of physical RAM installed. GRUB's
     "upper/lower memory" display uses the standard BIOS interface for
     the available memory in the first megabyte, or "lower memory", and
     a synthesized number from various BIOS interfaces of the memory
     starting at 1MB and going up to the first chipset hole for "upper
     memory" (the standard PC "upper memory" interface is limited to
     reporting a maximum of 64MB).

13.3.10 embed
-------------

 -- Command: embed stage1_5 device
     Embed the Stage 1.5 STAGE1_5 in the sectors after the MBR if
     DEVICE is a drive, or in the "boot loader" area if DEVICE is a FFS
     partition or a ReiserFS partition.(1) (*note embed-Footnote-1::)
     Print the number of sectors which STAGE1_5 occupies, if successful.

     Usually, you don't need to run this command directly. *Note
     setup::.

   (1) The latter feature has not been implemented yet.

13.3.11 find
------------

 -- Command: find filename
     Search for the file name FILENAME in all mountable partitions and
     print the list of the devices which contain the file. The file
     name FILENAME should be an absolute file name like
     `/boot/grub/stage1'.

13.3.12 fstest
--------------

 -- Command: fstest
     Toggle filesystem test mode.  Filesystem test mode, when turned
     on, prints out data corresponding to all the device reads and what
     values are being sent to the low-level routines. The format is
     `<PARTITION-OFFSET-SECTOR, BYTE-OFFSET, BYTE-LENGTH>' for
     high-level reads inside a partition, and `[DISK-OFFSET-SECTOR]'
     for low-level sector requests from the disk.  Filesystem test mode
     is turned off by any use of the `install' (*note install::) or
     `testload' (*note testload::) commands.

13.3.13 geometry
----------------

 -- Command: geometry drive [cylinder head sector [total_sector]]
     Print the information for the drive DRIVE. In the grub shell, you
     can set the geometry of the drive arbitrarily. The number of
     cylinders, the number of heads, the number of sectors and the
     number of total sectors are set to CYLINDER, HEAD, SECTOR and
     TOTAL_SECTOR, respectively. If you omit TOTAL_SECTOR, then it will
     be calculated based on the C/H/S values automatically.

13.3.14 halt
------------

 -- Command: halt `--no-apm'
     The command halts the computer. If the `--no-apm' option is
     specified, no APM BIOS call is performed. Otherwise, the computer
     is shut down using APM.

13.3.15 help
------------

 -- Command: help `--all' [pattern ...]
     Display helpful information about builtin commands. If you do not
     specify PATTERN, this command shows short descriptions of most of
     available commands. If you specify the option `--all' to this
     command, short descriptions of rarely used commands (such as *Note
     testload::) are displayed as well.

     If you specify any PATTERNS, it displays longer information about
     each of the commands which match those PATTERNS.

13.3.16 impsprobe
-----------------

 -- Command: impsprobe
     Probe the Intel Multiprocessor Specification 1.1 or 1.4
     configuration table and boot the various CPUs which are found into
     a tight loop. This command can be used only in the Stage 2, but
     not in the grub shell.

13.3.17 initrd
--------------

 -- Command: initrd file ...
     Load an initial ramdisk for a Linux format boot image and set the
     appropriate parameters in the Linux setup area in memory. See also
     *Note GNU/Linux::.

13.3.18 install
---------------

 -- Command: install [`--force-lba'] [`--stage2=os_stage2_file']
          stage1_file [`d'] dest_dev stage2_file [addr] [`p']
          [config_file] [real_config_file]
     This command is fairly complex, and you should not use this command
     unless you are familiar with GRUB. Use `setup' (*note setup::)
     instead.

     In short, it will perform a full install presuming the Stage 2 or
     Stage 1.5(1) (*note install-Footnote-1::) is in its final install
     location.

     In slightly more detail, it will load STAGE1_FILE, validate that
     it is a GRUB Stage 1 of the right version number, install in it a
     blocklist for loading STAGE2_FILE as a Stage 2. If the option `d'
     is present, the Stage 1 will always look for the actual disk
     STAGE2_FILE was installed on, rather than using the booting drive.
     The Stage 2 will be loaded at address ADDR, which must be `0x8000'
     for a true Stage 2, and `0x2000' for a Stage 1.5. If ADDR is not
     present, GRUB will determine the address automatically. It then
     writes the completed Stage 1 to the first block of the device
     DEST_DEV. If the options `p' or CONFIG_FILE are present, then it
     reads the first block of stage2, modifies it with the values of
     the partition STAGE2_FILE was found on (for `p') or places the
     string CONFIG_FILE into the area telling the stage2 where to look
     for a configuration file at boot time. Likewise, if
     REAL_CONFIG_FILE is present and STAGE2_FILE is a Stage 1.5, then
     the Stage 2 CONFIG_FILE is patched with the configuration file
     name REAL_CONFIG_FILE. This command preserves the DOS BPB (and for
     hard disks, the partition table) of the sector the Stage 1 is to
     be installed into.

     *Caution:* Several buggy BIOSes don't pass a booting drive
     properly when booting from a hard disk drive. Therefore, you will
     unfortunately have to specify the option `d', whether your Stage2
     resides at the booting drive or not, if you have such a BIOS. We
     know these are defective in this way:


          Fujitsu LifeBook 400 BIOS version 31J0103A


          HP Vectra XU 6/200 BIOS version GG.06.11

     *Caution2:* A number of BIOSes don't return a correct LBA support
     bitmap even if they do have the support. So GRUB provides a
     solution to ignore the wrong bitmap, that is, the option
     `--force-lba'. Don't use this option if you know that your BIOS
     doesn't have LBA support.

     *Caution3:* You must specify the option `--stage2' in the grub
     shell, if you cannot unmount the filesystem where your stage2 file
     resides. The argument should be the file name in your operating
     system.

   (1) They're loaded the same way, so we will refer to the Stage 1.5
as a Stage 2 from now on.

13.3.19 ioprobe
---------------

 -- Command: ioprobe drive
     Probe I/O ports used for the drive DRIVE. This command will list
     the I/O ports on the screen. For technical information, *Note
     Internals::.

13.3.20 kernel
--------------

 -- Command: kernel [`--type=type'] [`--no-mem-option'] file ...
     Attempt to load the primary boot image (Multiboot a.out or ELF,
     Linux zImage or bzImage, FreeBSD a.out, NetBSD a.out, etc.) from
     FILE. The rest of the line is passed verbatim as the "kernel
     command-line". Any modules must be reloaded after using this
     command.

     This command also accepts the option `--type' so that you can
     specify the kernel type of FILE explicitly. The argument TYPE must
     be one of these: `netbsd', `freebsd', `openbsd', `linux',
     `biglinux', and `multiboot'. However, you need to specify it only
     if you want to load a NetBSD ELF kernel, because GRUB can
     automatically determine a kernel type in the other cases, quite
     safely.

     The option `--no-mem-option' is effective only for Linux. If the
     option is specified, GRUB doesn't pass the option `mem=' to the
     kernel.  This option is implied for Linux kernels 2.4.18 and newer.

13.3.21 lock
------------

 -- Command: lock
     Prevent normal users from executing arbitrary menu entries. You
     must use the command `password' if you really want this command to
     be useful (*note password::).

     This command is used in a menu, as shown in this example:

          title This entry is too dangerous to be executed by normal users
          lock
          root (hd0,a)
          kernel /no-security-os

     See also *Note Security::.

13.3.22 makeactive
------------------

 -- Command: makeactive
     Set the active partition on the root disk to GRUB's root device.
     This command is limited to _primary_ PC partitions on a hard disk.

13.3.23 map
-----------

 -- Command: map to_drive from_drive
     Map the drive FROM_DRIVE to the drive TO_DRIVE. This is necessary
     when you chain-load some operating systems, such as DOS, if such
     an OS resides at a non-first drive. Here is an example:

          grub> map (hd0) (hd1)
          grub> map (hd1) (hd0)

     The example exchanges the order between the first hard disk and the
     second hard disk. See also *Note DOS/Windows::.

13.3.24 md5crypt
----------------

 -- Command: md5crypt
     Prompt to enter a password, and encrypt it in MD5 format. The
     encrypted password can be used with the command `password' (*note
     password::). See also *Note Security::.

13.3.25 module
--------------

 -- Command: module file ...
     Load a boot module FILE for a Multiboot format boot image (no
     interpretation of the file contents are made, so the user of this
     command must know what the kernel in question expects). The rest
     of the line is passed as the "module command-line", like the
     `kernel' command. You must load a Multiboot kernel image before
     loading any module. See also *Note modulenounzip::.

13.3.26 modulenounzip
---------------------

 -- Command: modulenounzip file ...
     The same as `module' (*note module::), except that automatic
     decompression is disabled.

13.3.27 pause
-------------

 -- Command: pause message ...
     Print the MESSAGE, then wait until a key is pressed. Note that
     placing <^G> (ASCII code 7) in the message will cause the speaker
     to emit the standard beep sound, which is useful when prompting
     the user to change floppies.

13.3.28 quit
------------

 -- Command: quit
     Exit from the grub shell `grub' (*note Invoking the grub shell::).
     This command can be used only in the grub shell.

13.3.29 reboot
--------------

 -- Command: reboot
     Reboot the computer.

13.3.30 read
------------

 -- Command: read addr
     Read a 32-bit value from memory at address ADDR and display it in
     hex format.

13.3.31 root
------------

 -- Command: root device [hdbias]
     Set the current "root device" to the device DEVICE, then attempt
     to mount it to get the partition size (for passing the partition
     descriptor in `ES:ESI', used by some chain-loaded boot loaders),
     the BSD drive-type (for booting BSD kernels using their native
     boot format), and correctly determine the PC partition where a BSD
     sub-partition is located. The optional HDBIAS parameter is a
     number to tell a BSD kernel how many BIOS drive numbers are on
     controllers before the current one. For example, if there is an
     IDE disk and a SCSI disk, and your FreeBSD root partition is on
     the SCSI disk, then use a `1' for HDBIAS.

     See also *Note rootnoverify::.

13.3.32 rootnoverify
--------------------

 -- Command: rootnoverify device [hdbias]
     Similar to `root' (*note root::), but don't attempt to mount the
     partition. This is useful for when an OS is outside of the area of
     the disk that GRUB can read, but setting the correct root device
     is still desired. Note that the items mentioned in `root' above
     which derived from attempting the mount will _not_ work correctly.

13.3.33 savedefault
-------------------

 -- Command: savedefault num
     Save the current menu entry or NUM if specified as a default
     entry. Here is an example:

          default saved
          timeout 10

          title GNU/Linux
          root (hd0,0)
          kernel /boot/vmlinuz root=/dev/sda1 vga=ext
          initrd /boot/initrd
          savedefault

          title FreeBSD
          root (hd0,a)
          kernel /boot/loader
          savedefault

     With this configuration, GRUB will choose the entry booted
     previously as the default entry.

     You can specify `fallback' instead of a number. Then, next
     fallback entry is saved. Next fallback entry is chosen from
     fallback entries. Normally, this will be the first entry in
     fallback ones.

     See also *Note default:: and *Note Invoking grub-set-default::.

13.3.34 setup
-------------

 -- Command: setup [`--force-lba'] [`--stage2=os_stage2_file']
          [`--prefix=dir'] install_device [image_device]
     Set up the installation of GRUB automatically. This command uses
     the more flexible command `install' (*note install::) in the
     backend and installs GRUB into the device INSTALL_DEVICE. If
     IMAGE_DEVICE is specified, then find the GRUB images (*note
     Images::) in the device IMAGE_DEVICE, otherwise use the current
     "root device", which can be set by the command `root'. If
     INSTALL_DEVICE is a hard disk, then embed a Stage 1.5 in the disk
     if possible.

     The option `--prefix' specifies the directory under which GRUB
     images are put. If it is not specified, GRUB automatically
     searches them in `/boot/grub' and `/grub'.

     The options `--force-lba' and `--stage2' are just passed to
     `install' if specified. *Note install::, for more information.

13.3.35 testload
----------------

 -- Command: testload file
     Read the entire contents of FILE in several different ways and
     compare them, to test the filesystem code. The output is somewhat
     cryptic, but if no errors are reported and the final `i=X,
     filepos=Y' reading has X and Y equal, then it is definitely
     consistent, and very likely works correctly subject to a
     consistent offset error. If this test succeeds, then a good next
     step is to try loading a kernel.

13.3.36 testvbe
---------------

 -- Command: testvbe mode
     Test the VESA BIOS EXTENSION mode MODE. This command will switch
     your video card to the graphics mode, and show an endless
     animation. Hit any key to return. See also *Note vbeprobe::.

13.3.37 uppermem
----------------

 -- Command: uppermem kbytes
     Force GRUB to assume that only KBYTES kilobytes of upper memory
     are installed. Any system address range maps are discarded.

     *Caution:* This should be used with great caution, and should only
     be necessary on some old machines. GRUB's BIOS probe can pick up
     all RAM on all new machines the author has ever heard of. It can
     also be used for debugging purposes to lie to an OS.

13.3.38 vbeprobe
----------------

 -- Command: vbeprobe [mode]
     Probe VESA BIOS EXTENSION information. If the mode MODE is
     specified, show only the information about MODE. Otherwise, this
     command lists up available VBE modes on the screen. See also *Note
     testvbe::.

