The command root simplies the specication of kernel and initrd les. The only
argument of root is a device or a partition. This device is used for all kernel, initrd,
or other le paths for which no device is explicitly specied until the next root com-
mand.
The boot command is implied at the end of every menu entry, so it does not need to
be written into the menu le. However, if you use GRUB interactively for booting, you
must enter the boot command at the end. The command itself has no arguments. It
merely boots the loaded kernel image or the specied chain loader.
After writing all menu entries, dene one of them as the default entry. Otherwise,
the rst one (entry 0) is used. You can also specify a time-out in seconds after which
the default entry should boot. timeout and default usually precede the menu entries.
An example le is described in Section 9.1.1.2, “An Example Menu File” (page 160).
9.1.1.1 Naming Conventions for Hard Disks and
Partitions
The naming convention GRUB uses for hard disks and partitions differ from that used
for normal Linux devices. It more closely resembles the simple disk enumeration the
BIOS does and the syntax is similar to that used in some BSD derivatives. In GRUB,
the numbering of the partitions start with zero. This means that (hd0,0) is the rst
partition of the rst hard disk. On a common desktop machine with a hard disk connected
as primary master, the corresponding Linux device name is /dev/sda1.
The four possible primary partitions are assigned the partition numbers 0 to 3. The
logical partitions are numbered from 4:
(hd0,0) first primary partition of the first hard disk
(hd0,1) second primary partition
(hd0,2) third primary partition
(hd0,3) fourth primary partition (usually an extended partition)
(hd0,4) first logical partition
(hd0,5) second logical partition
Being dependent on BIOS devices, GRUB does not distinguish between PATA (IDE),
SATA, SCSI, and hardware RAID devices. All hard disks recognized by the BIOS or
other controllers are numbered according to the boot sequence preset in the BIOS.
The Boot Loader GRUB 159
