I'm wanting to add 2 80 GB hard drives, configured as a RAID 1 to my server. It's running Debian 3.1, the kernal is 2.4. I feel I can tar the current /home directory and untar it on the RAID. I can then edit my fstab to mount the RAID as /home, my concern is how do I tell adduser where the new /home directories go?

Mmm, maybe I'm missing something, but once the system is set up to mount the new /home directory instead of the old one, shouldn't everything work just the same as before? I mean, it doesn't matter what physical disk /home is on, as long as the system knows where to find it, right?

David is right. Build the RAID as you should, then create a filesystem on the disks, open /etc/fstab and comment out the existing /home entry. Add the new /home space to the fstab file, adapt the device path to suit your system.

To copy the old /home to the new /home, uncomment the old /home entry (in /etc/fstab), make sure to change it's path (like /home/oldhome) but create the new directory beforehand. Copy the files to their new home (), make sure you've got them all (there are several hidden files, all starting with a dot) and when you're done, remove the entry in /etc/fstab to the old /home.

One thing I forgot to add, the RAID is seperate from the system drive. I just want /home diretories on the RAID. Will tha tmake a difference?
Thaniks for the answers so far. I'm about to start on this in the near future.

Separating your /home from the rest of the system is generally a good idea, so go ahead. For Linux it doesn't matter your RAID for /home is on separate disks, just make sure you set the RAID up correctly.

What everyone here is saying is correct, if the mount point is the same the user will not know the difference. The device which it is mounted under is totally transparent to the user, so whether is is /dev/hda1, /dev/hda7 or /dev/hdb6 etc.... Also before you do anything make sure you backup all the data first, nothing like getting a call from an angry user who just losts some important data. Also depending on what raid you setup make sure you have a good backup plan, if you use mirroring raid your ok, but if you use stripping raid that splits the data onto both drives and one drive fails, you'll lose all your data.