I found an old computer that I want to use as a router. Right now, I've installed Ubuntu Linux on it. When trying to boot, I get a DISK BOOT FAILURE error message from the BIOS. I tried putting GRUB on a boot disk, but I get error 21 (it can't see the disk).

There doesn't seem to be anything physically wrong with the disk; I can mount, read, and write it fine by executing a shell on the install CD. The BIOS auto-detects the disk okay with the following settings:

Size: 2112
Cyls: 4092
Head: 16
Precomp: 65535
Landz: 4091
Sector: 63
Mode: Normal

I don't believe there is anything wrong with the BIOS either. When I got the machine, it had a beta version of the Award BIOS, which I replaced with the latest stable release. I have not run into any differences between the two versions.

Can anyone think of any reason GRUB and the BIOS might not be able to read the disk when the Ubuntu install CD can? If not, can anyone think of a work around? I've thought of compiling a small kernel, putting it on the floppy with an initrd, and booting from that, but I'd rather avoid compiling a kernel on such a slow machine.

Thanks in advance

Two things to verify in the BIOS; probably under CMOS settings.

1) check the order of disk polling; should be A,CDROM,C (check floppy drive first, then cd drive, than harddrive).

2) select the drive and edit these four settings as needed: cylinders, heads, sectors, and mode. They should be the same as in your post.

If the BIOS still doesn't boot the disk, there may be something wrong with it that isn't obvious.

I'm assuming Unbunt is the only OS on the disk. So, why make a boot floppy instead on writing the first stage of grub to the MBR?

With grub not booting properly, I'd need to see /boot/grub/grub.conf and /etc/fstab to see if there is a discrepancy between grub.conf and fstab to account for the problem.