The root user is not allowed to login on several linux distributions by default (Especially the ones have GNOME).
To enable root login, apply these commands (It has been tried under Fedora 16. Probably It has similar procedure for other linux systems):
- Open configuration file:
su -gedit /etc/pam.d/gdm
- Find that line and add “#” to beginning of the line. Then save it.
# auth required pam_succeed_if.so user != root quiet
- Do the same thing for
/etc/pam.d/gdm-passwordfile.