What Mark said. But also:
I recommend the "reachable directory" method.
(That's what SuSE calls it; I forget what RedHat calls it.)
In this method, you mount the CD manually one of three ways ...
as an FBA (if you can swing that! good luck!)
by way of "loopback" if you have other Linux/390 media
via NFS (where the CD or CD image is mounted on
some othe UNIX system and served via NFS from there)
Once you have manually mounted the CD content,
you will have elimiated most of the network errors Mark eludes to
that would require you to restart.
This is probably hard to figure out,
but once you've figured it out and arranged things
(like the NFS server, for example) it is really easy to DO.
