From Fedora Project Wiki
Unlike KDM, GDM outsources services such as shutdown, restart and parts of session switching to a lower-level component. Until and including Fedora 16, that component was ConsoleKit. Starting from Fedora 17, it is systemd. Support for systemd in kde-workspace was developed in Fedora and needs testing.
You need to have the gdm package installed - yum install gdm.
How to test
- If your current display manager is KDM, switch to use GDM:
- Switch to a virtual terminal using Ctrl+Fkeys
- Login as root, and stop the KDM service: service kdm stop
- Start GDM: service gdm start. GDM login screen should now appear.
- If autologin to GNOME was enabled, start by logging out of GNOME.
- Log into KDE Plasma Desktop. (GDM allows selecting the session type after you enter the user name, on the password prompt screen.)
- Try shutting down, rebooting or switching users from the KDE Plasma Desktop Workspace. If you are using the live image, you can limit the testing only to user switching for your convenience.
- Shutdown and restart should work.
- User switching should also work.