I installed Debian onto a USB drive and grub quit on the main drive.

The error message is:

GRUB Loading stage1.5
GRUB loading, please wait...
Error 21

The disks partitions are:

hda1: Windows XP
hda2: Linux ext3, Debian Stable
hda5: Linux Swap
sda1: Linux ext3
sda2: Linux swap

It used to boot to hda using GRUB. After installing Debian on sda, I just get Error 21.

How can I get the computer to boot again?

Error 21 means Hard Disk not found.. http://orgs.man.ac.uk/documentation/grub/grub_14.html

So SDA is an external USB Hard Drive ? Maybe this how-to will shed some light on what you need to do to fix it. The How to is for Installing Ubuntu on a USB Hard drive. Ubuntu is basically Debain so the process should be the same.

http://www.ubuntuforums.org/showthread.php?t=80811

Yes, SDA is an external USB drive.

I don't see how that HOWTO helps. The only GRUB reference to SDA is in device.map where /dev/hda defines hd0 and /dev/sda defines hd1. I don't see a reference to hd1 in menu.lst.

Here is my menu.lst, without comments:
default 0

timeout 5

color cyan/blue white/blue

title Debian GNU/Linux, kernel 2.6.8-2-386
root (hd0,1)
kernel /boot/vmlinuz-2.6.8-2-386 root=/dev/hda2 ro
initrd /boot/initrd.img-2.6.8-2-386
savedefault
boot

title Debian GNU/Linux, kernel 2.6.8-2-386 (recovery mode)
root (hd0,1)
kernel /boot/vmlinuz-2.6.8-2-386 root=/dev/hda2 ro single
initrd /boot/initrd.img-2.6.8-2-386
savedefault
boot

title Other operating systems:
root

title Microsoft Windows XP Home Edition
root (hd0,0)
savedefault
makeactive
chainloader +1


It all looks OK to me, but I still get an error.

hello, this is my first post, and I am from Argentina. I have a problem after installing the Debian Etch on a USB disc, Grub says: "Grub Error 21". I can't see the menu.lst and /boot doesn't even exist. Could somebody help me? Thanks