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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 either used in the menu or in the menu entries.
13.1 The list of commands for the menu only 13.2 The list of general commands 13.3 The list of command-line and menu entry commands
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The semantics used in parsing the configuration file are the following:
These commands can only be used in the menu:
13.1.1 default Set the default entry 13.1.2 fallback Set the fallback entry 13.1.3 hiddenmenu Hide the menu interface 13.1.4 timeout Set the timeout 13.1.5 title Start a menu entry
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You can specify `saved' instead of a number. In this case, the
default entry is the entry saved with the command
savedefault
. See section 13.3.33 savedefault, for more information.
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default
command (see section 13.1.1 default)). This obviously won't help if the machine was
rebooted by a kernel that GRUB loaded.
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Commands usable both in the menu and in the command-line.
13.2.1 bootp Initialize a network device via BOOTP 13.2.2 color Color the menu interface 13.2.3 device Specify a file as a drive 13.2.4 dhcp Initialize a network device via DHCP 13.2.5 hide Hide a partition 13.2.6 ifconfig Configure a network device manually 13.2.7 pager Change the state of the internal pager 13.2.8 partnew Make a primary partition 13.2.9 parttype Change the type of a partition 13.2.10 password Set a password for the menu interface 13.2.11 rarp Initialize a network device via RARP 13.2.12 serial Set up a serial device 13.2.13 setkey Configure the key map 13.2.14 terminal Choose a terminal 13.2.15 terminfo Define escape sequences for a terminal 13.2.16 tftpserver Specify a TFTP server 13.2.17 unhide Unhide a partition
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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'.
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foreground/background
. foreground and
background are symbolic color names. A symbolic color name must be
one of these:
These below can be specified only for the foreground.
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 |
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grub> device (fd0) /floppy-image grub> device (hd0) /dev/sd0 |
This command can be used only in the grub shell (see section 15. Invoking the grub shell).
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bootp
, since the two
protocols are very similar. This command is only available if GRUB is
compiled with netboot support. See also 6. Downloading OS images from a 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'.
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0-0xff
; from and
to are the starting and ending sectors, expressed as an absolute
sector number.
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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 continueing. The option
`--md5' tells GRUB that passwd is encrypted with
md5crypt
(see section 13.3.24 md5crypt).
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The serial port is not used as a communication channel unless the
terminal
command is used (see section 13.2.14 terminal).
This command is only available if GRUB is compiled with serial support. See also 7. Using GRUB via a serial line.
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grub> setkey capslock control grub> setkey control capslock |
A key must be an alphabet, 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:
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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.
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You can use the utility grub-terminfo
to generate
appropriate arguments to this command. See section 18. Invoking grub-md5-crypt.
If no option is specified, the current settings are printed.
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ifconfig
(see section 13.2.6 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 6. Downloading OS images from a network.
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These commands are usable in the command-line and in menu entries. If
you forget a command, you can run the command help
(see section 13.3.15 help).
13.3.1 blocklist Get the block list notation of a file 13.3.2 boot Start up your operating system 13.3.3 cat Show the contents of a file 13.3.4 chainloader Chain-load another boot loader 13.3.5 cmp Compare two files 13.3.6 configfile Load a configuration file 13.3.7 debug Toggle the debug flag 13.3.8 displayapm Display APM information 13.3.9 displaymem Display memory configuration 13.3.10 embed Embed Stage 1.5 13.3.11 find Find a file 13.3.12 fstest Test a filesystem 13.3.13 geometry Manipulate the geometry of a drive 13.3.14 halt Shut down your computer 13.3.15 help Show help messages 13.3.16 impsprobe Probe SMP 13.3.17 initrd Load an initrd 13.3.18 install Install GRUB 13.3.19 ioprobe Probe I/O ports used for a drive 13.3.20 kernel Load a kernel 13.3.21 lock Lock a menu entry 13.3.22 makeactive Make a partition active 13.3.23 map Map a drive to another 13.3.24 md5crypt Encrypt a password in MD5 format 13.3.25 module Load a module 13.3.26 modulenounzip Load a module without decompression 13.3.27 pause Wait for a key press 13.3.28 quit Exit from the grub shell 13.3.29 reboot Reboot your computer 13.3.30 read Read data from memory 13.3.31 root Set GRUB's root device 13.3.32 rootnoverify Set GRUB's root device without mounting 13.3.33 savedefault Save current entry as the default entry 13.3.34 setup Set up GRUB's installation automatically 13.3.35 testload Load a file for testing a filesystem 13.3.36 testvbe Test VESA BIOS EXTENSION 13.3.37 uppermem Set the upper memory size 13.3.38 vbeprobe Probe VESA BIOS EXTENSION
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grub> cat /etc/fstab |
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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.
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Usually, you don't need to run this command directly. See section 13.3.34 setup.
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/boot/grub/stage1
.
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install
(see section 13.3.18 install) or testload
(see section 13.3.35 testload) commands.
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If you specify any patterns, it displays longer information about each of the commands which match those patterns.
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setup
(see section 13.3.34 setup)
instead.
In short, it will perform a full install presuming the Stage 2 or Stage 1.5(9) 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 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 have to specify the option `d', whether your Stage2 resides at the booting drive or not, if you have such a BIOS unfortunately. We know these are defective in that:
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.
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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.
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password
if you really want this command to be
useful (see section 13.2.10 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 |
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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 4.2.6 DOS/Windows.
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password
(see section 13.2.10 password). See also 9. Protecting your computer from cracking.
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kernel
command. You must load a Multiboot kernel image before
loading any module. See also 13.3.26 modulenounzip.
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module
(see section 13.3.25 module), except that automatic
decompression is disabled.
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grub
(see section 15. Invoking the grub shell). This command can be used only in the grub shell.
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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 13.3.32 rootnoverify.
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root
(see section 13.3.31 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.
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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. See also 13.1.1 default.
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install
(see section 13.3.18 install) in the backend
and installs GRUB into the device install_device. If
image_device is specified, then find the GRUB images
(see section 10. GRUB image files) 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. See section 13.3.18 install, for more
information.
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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.
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