How to get a login box for server & diskless terminal clients
without having to enter stuff at boot every time.
Whats the command to bring up a login box?

Also what's the environment variable that holds the user ID?
I want user IDs for the names of the clients home dirs., or I
may have to use MAC addresses or something nasty like that.

Using KDE, may switch to IceWM, at least on the server.
Poormans install on Knoppix 3.3