GRUB contains a number of different commands that may be executed
interactively in the command line interface. Some of the commands accept
options after their name, and these options should be separated from the
command and other options on that line by space characters.
boot — Boots the operating system or chain
loader that has been previously specified and loaded.
chainloader
<file-name> — Loads
the specified file as a chain loader. To grab the file at the first
sector of the specified partition, you can use
+1 as the file's name.
displaymem — Displays the current use of
memory, based on information from the BIOS. This is useful if you
are not sure how much RAM a system has and have yet to boot it.
initrd
<file-name> —
Allows you to specify an initial RAM disk to use when booting,
necessary when the kernel needs certain modules in order to boot
properly.
install
<stage-1>
<install-disk>
<stage-2> p
<config-file> — Installs GRUB
to your MBR. This allows the GRUB interfaces to come up when the
system is rebooted.
 | Warning |
|---|
| | This command will write over anything else in your MBR. If
executed, anything you have been using to boot your operating
system other than GRUB will be lost.
Make sure you know what you are doing before you execute this
command.
|
This command can be configured in several different ways. However,
you must specify a
<stage-1>, which
signifies a device, partition, and file where the first boot loader
image can be found, such as (hd0,0)/grub/stage1. In
addition, you must specify the disk where the stage 1 boot loader
should be installed, such as (hd0).
The <stage-2>
section tells the stage 1 boot loader where the stage 2 boot loader
is located, such as (hd0,0)/grub/stage2. The
p option tells the install
command that a menu configuration file is being specified in the
<config-file>
section, such as (hd0,0)/grub/grub.conf.
kernel <kernel-file-name>
<option-1>
<option-N> —
Specifies the kernel file to load from GRUB's root filesystem when
using direct loading to boot the operating system. Options can
follow the kernel command that will be passed to
the kernel when it is loaded.
For Red Hat Linux, you may have a line that looks like this:
kernel /vmlinuz root=/dev/hda5 |
This line specifies that the vmlinuz file is loaded
from GRUB's root filesystem, such as
(hd0,0). An option is also passed to the kernel
specifying that the root filesystem for the Linux kernel when it
loads should be on hda5, the fifth partition on
the first IDE hard drive. Multiple options may be placed after this
option, if you need them.
root
<device-and-partition>
— Configures GRUB's root partition to be the particular device
and partition, such as (hd0,0), and mounts the
partition so that files can be read.
rootnoverify
<device-and-partition>
— Does the same thing as the root command
but does not mount the partition.
Commands other than these are available. Type info
grub for a full list of all commands.
