How do you get around this:
gdm:x:120:120:Gnome Display Manager:/var/lib/gdm:/sbin/nologin
su, gksu say account is not available. Do you just change the :sbin/nologin part? How -- safely? I've never messed with something like that before.
This is what I use to do, if something is wrong somebody please correct me.
Change :/sbin/nologin to :/bin/bash, then, as root # su gdm $ dbus-launch gnome-appearance-properties
Configure according to your needs, then edit /etc/passwd again and change :/bin/bash to :/sbin/nologin.