Node:Device map, Previous:Installation under UNIX, Up:Invoking the grub shell

The map between BIOS drives and OS devices

When you specify the option --device-map (see Basic usage), the grub shell creates the device map file automatically unless it already exists. The file name /boot/grub/ is preferred.

If the device map file exists, the grub shell reads it to map BIOS drives to OS devices. This file consists of lines like this:

device file

device is a drive, which syntax is the same as the one in GRUB (see Device syntax), and file is an OS's file, which is normally a device file.

The reason why the grub shell gives you the device map file is that it cannot guess the map between BIOS drives and OS devices correctly in some environments. For example, if you exchange the boot sequence between IDE and SCSI in your BIOS, it mistakes the order.

Thus, edit the file if the grub shell makes a mistake. You can put any comments in the file if needed, as the grub shell assumes that a line is just a comment if the first character is #.