How do I reset my GDM configuration?

Question

My friend lent me her laptop and she followed some tutorial on how to switch the wallpaper in GDM2 but it didn't work and now it's stuck with some wallpaper I can't seem to get rid of, how do I reset GDMs config?

Solution

Open a gnome-terminal (Alt + F2 → gnome-terminal) and type the following:

• To only reset the background:

  sudo -u gdm gconftool-2 --unset /desktop/gnome/background/picture_filename
  

• To reset all of GDM's configuration:

  sudo -u gdm gconftool-2 --recursive-unset /
  

The second one will take a bit, both commands will ask you for your password.