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, use
+1 as the file's name.
displaymem — Displays the current use
of memory, based on information from the BIOS. This is useful to
determine how much RAM a system has prior to booting it.
initrd
<file-name> —
Enables users 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 the system MBR. This allows the GRUB interfaces to come up when
the system is rebooted.
 | Warning |
|---|
| | The install command will overwrite any
other information in the MBR. If executed, any information (other
than GRUB information) that is used to boot other operating
systems, will be lost.
Make sure to have the proper knowledge before executing this
command.
|
This command can be configured in several different
ways. However, it is required to 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, 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 and will be passed to
the kernel when it is loaded.
For Red Hat Linux, an example kernel command looks
like the following:
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 needed.
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.
