Can't load display manager

F18 on an old R40

Originally did an XFCE install.

Installed MATE. Got sick of trying to get lightdm to auto log in.

removed lightdm after installing gdm

gdm would not auto start. Had to log in and launch it manually. Spent a while trying to figure out how gdm starts - could not find it. Searched net / Fedora Forums etc. No joy.

gave up. gdm uses too much memory anyway.

Reinstalled lightdm - again, not starting automatically. type 'lightdm' and it works.

init 5 does not work either.

My question is - where the heck does this monolithic heap of junk set what display manager it loads by default and how can I get it to load lightdm on boot?

thanks