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Chapter 2. The GRUB Boot Loader
One of the most important things to understand before using GRUB is how the program refers
to devices, such as hard drives and partitions. This information is particularly important when
configuring GRUB to boot multiple operating systems.
4.1. Device Names
When referring to a specific device with GRUB, do so using the following format (note that the
parentheses and comma are very important syntactically):
(<type-of-device><bios-device-number>,<partition-number>)
The
<type-of-device>
common options are
hd
available called
for a network disk. Instructions on configuring GRUB to boot over the
nd
network are available online at http://www.gnu.org/software/grub/manual/.
The
<bios-device-number>
numbered
and a secondary IDE hard drive is numbered
0
that used for devices by the kernel. For example, the
in
for GRUB, the
0
hd0
The
<partition-number>
<bios-device-number>
partitions are specified using letters, with
Tip
The numbering system for devices under GRUB always begins with
Failing to make this distinction is one of the most common mistakes made by
new users.
To give an example, if a system has more than one hard drive, GRUB refers to the first hard
drive as
and the second as
(hd0)
drive as
and the third partition on the second hard drive as
(hd0,0)
In general the following rules apply when naming devices and partitions under GRUB:
• It does not matter if system hard drives are IDE or SCSI, all hard drives begin with the letters
. The letters
are used to specify 3.5 diskettes.
hd
fd
• To specify an entire device without respect to partitions, leave off the comma and the partition
number. This is important when telling GRUB to configure the MBR for a particular disk. For
example,
specifies the MBR on the first device and
(hd0)
fourth device.
16
specifies the type of device from which GRUB boots. The two most
for a hard disk or
for a 3.5 diskette. A lesser used device type is also
fd
is the BIOS device number. The primary IDE hard drive is
in
is analogous to the
b
hdb
specifies the number of a partition on a device. Like the
, most types of partitions are numbered starting at
corresponding to
a
. Likewise, GRUB refers to the first partition on the first
(hd1)
. This syntax is roughly equivalent to
1
in
for the kernel is analogous to the
a
hda
in
, and so on.
1
hd1
,
corresponding to
0
b
(hd1,2)
specifies the MBR on the
(hd3)
. However, BSD
0
, and so on.
1
, not
.
0
1
.
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