I have an Ubuntu server (9.04 at the moment) and an Ubuntu desktop which I recently upgraded to 10.04. Once I'd set up the users and groups on the desktop to match the server (I'm new to this, I think LDAP would do this for me, but that's another question), the friendly greeter screen no longer displays the same set of users¹. In 9.04 (the previous version running on the desktop PC) there were four users shown. These had UIDs of 500 to 510. Changing the UIDs is one solution, but that would mean changing the UIDs on all my linux PCs, and that is a might PITA (unless there's a tool to make it less painful).

How can I get the greeter in 10.04 to show users with UIDs in the 500s without resorting to changing the UIDs?

1. I use the greeter screen with user pictures as the PC is mainly for use by my young children and clicking the picture is a bit easier (they still need to type a password though).