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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 used either anywhere in the menu or specifically 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. You can specify multiple
fallback entry numbers.
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Commands usable anywhere 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 is
the starting address and len is the length, both in sector units.
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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 continuing. 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 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:
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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-terminfo.
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(10) 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:
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. This option is implied for Linux kernels 2.4.18 and newer.
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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.
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 13.1.1 default and 19. Invoking grub-set-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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