GRUB supports the no emulation mode in the El Torito
specification1. This means that you can use the whole CD-ROM
from GRUB and you don't have to make a floppy or hard disk image file,
which can cause compatibility problems.
For booting from a CD-ROM, GRUB uses a special Stage 2 called
stage2_eltorito. The only GRUB files you need to have in your
bootable CD-ROM are this stage2_eltorito and optionally a config file
menu.lst. You don't need to use stage1 or stage2,
because El Torito is quite different from the standard boot process.
Here is an example of procedures to make a bootable CD-ROM
image. First, make a top directory for the bootable image, say,
This produces a file named grub.iso, which then can be burned
into a CD (or a DVD). mkisofs has already set up the disc to boot
from the boot/grub/stage2_eltorito file, so there is no need to
setup GRUB on the disc. (Note that the -boot-load-size 4 bit is
required for compatibility with the BIOS on many older machines.)
You can use the device `(cd)' to access a CD-ROM in your
config file. This is not required; GRUB automatically sets the root device
to `(cd)' when booted from a CD-ROM. It is only necessary to refer to
`(cd)' if you want to access other drives as well.
 El Torito is a specification for bootable CD
using BIOS functions.
Published under the terms of the GNU General Public License