I'm using Ubuntu 8.04 but I'd like to try some other distributions; unfortunately, this is going to mean some screwing around with my partitions. Basically I'm going to have to move my root partition (with /boot, since it's not on its own partition) elsewhere. I understand in a basic way how to do this -- basically, create a new partition and copy the contents of the old one to it, and then I'm going to have to edit /boot/grub/menu.lst so that everything knows where it is. But I can't figure out how to actually reinstall GRUB.

I'm going to be doing the actual partitioning from a live CD but I don't know how to then reinstall GRUB and tell stage 1 where to find stage 2 (I think I have a handle on what those things are.) I'm going to have to reinstall GRUB on the MBR, correct? But how do I tell it where to look for stage 2? My understanding is that there's only one command line parameter to pass grub-install, which is where to put stage 1.

You need to install grub while running in the / partition where the grub stage2 is located. The way to do that is to:

boot from a live CD

mount the correct / partition

chroot to the correct / partition

If /boot is a separate partition then mount /boot

run grub-install

reboot

---------------------
Steve Stites

if you get for example (hd0,1),then
will install grub from that partition and
will install it on the MBR.(hd0,1) will install it on that partition and (hd1,x)on the second HD and so on.

I don't even bother with the chroot - I usually just run the grub command, either from the installed system, or from the liveCD itself. grub-install being merely a wrapper for the grub (sub-)commands.
Not something to stress over - easy to fix even if it goes wrong.

Great! Thanks all of you, this won't be a problem at all!