Red Hat LINUX 7.2 Reference Manual page 105

Section 5.2:Terminology
Remember that GRUB's numbering system for devices starts at 0, and not
1. This is one of the most common mistakes made by new GRUB users.
The <partition-number> relates to the number of a specific partition on that device. Like the
<bios-device-number> , the numbering of partitions starts at 0. While most partitions are spec-
ified by numbers, if your system uses BSD partitions, they are signified by letters, such as a or c.
GRUB uses the following rules when naming devices and partitions:
• It does not matter if your hard drives are IDE or SCSI. All hard drives start with hd. Floppy disks
start with fd.
• To specify an entire device without respect to its partitions, simply leave off the comma and the
partition number. This is important when telling GRUB to configure the MBR for a particular
disk. For example, (hd0) specifies the first device and (hd3) specifies the fourth device.
• It is very important, if you have multiple hard drives, to know their order according to the BIOS.
This is rather simple to do if you have only IDE or SCSI drives, but if you have a mix of them,
things get a bit more tricky.
5.2.2 File Names
When typing commands to GRUB involving a file, such as a menu list to use when allowing the booting
of multiple operating systems, you must include the file immediately after the specifying the device
and partition. A sample file specification to an absolute filename is organized like this:
( <type-of-device><bios-device-number> , <partition-number> )/ path / to / file
Most of the time, you will be specifying files by their path on that partition plus the file's name. This
is rather straightforward.
You can also specify files to GRUB that do not actually appear in the filesystem, such as a chain
loader that appears in the first few blocks of a partition. To specify these files, you have to provide a
blocklist, which tells GRUB, block by block, where the file is located in the partition. As a file can
be comprised of several different sets of blocks, there is a specific way to write blocklists. Each file's
section location is described by an offset number of blocks and then a number of blocks from that
offset point, and the sections are put together in order, separated by commas.
In other words, consider the following blocklist:
0+50,100+25,200+1
Note
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