Does anyone know a good source for this?

In my particular situation I have CentOS installed (basically redhat Enterprise) with grub as the boot loader, and want to install debian as well. I went through the debian install, added new partitions, then it said:
I figured I already had grub installed so I shouldn't install it again. But then I don't know how to continue the debian install process, or add debian as an option in the grub menu.

Look in /boot or /boot/grub for a conf or config file (or even grub.conf? Can't remember).

Copy the line that has title=CentOS and down from there and paste it below. Change the title line to equal something else, modify the kernel line ((hd0,0) for hda1 or sda1) and add the root command it said to the end of the kernel line.

Sorry, that was confusing. If you didn't get it, post your config file and I can change it for you.

Thanks. You got me to the next step. I came up with this:

title CentOS
root (hd0,0)
kernel /vmlinuz-2.4.21-20.EL.c0 ro root=LABEL/
initrd /initrd-2.4.21-20.EL.c0.img
title debian
root (hd0,4)
kernel /boot/vmlinuz-2.6.3-1-386 ro root=LABEL/
initrd /boot/initrd.img-2.6.3-1-386

I don't know why I debian needs /boot/ while CentOS can make do with simply /
This took me a while to figure out.
Here's one link that helped:
http://linux-universe.com/HOWTO/Kern.../grubconf.html

So now I get:
mount: /dev2/root2 is not a valid block device
mount: /dev2/root2 is not a valid block device
mount: /dev2/root2 is not a valid block device
mount: /dev2/root2 is not a valid block device
sigh. I haven't tried tracking down this on google yet. Maybe I'll just try installing debian first, then CentOS.

Replace LABEL/ with /dev/hda5.

Also, it would need /boot/ if you don't have a seperate boot partition.

If that doesn,t work, try title=<blah>, I think it needs the =, but not sure.

Thanks again for your reply. I think I did try your suggestion of replacing LABEL/ with /dev/hda5 but that it still failed. Not sure. In any case I know at least I solved the initial problem.

Now I'm going back, deleting CentOS and starting with debian first. Not ideal, but it's not critical either. At least I'm understanding grub.conf better now. Thanks for your help.

No problem, let me know if it works. Check the Gentoo handbook for a good grub explenation (gentoo.org/docs).

Same error 2nd time around?

You can go into the command-line and type 'grub'. Next, type root (hd0 the hit tab and it will tell you your partitions .