Cannot log on as root via GDM in Fedora 10
In Fedora 10 logging in as root via GDM has been disabled by default. For safety and security it is strongly recommended to log in as a regular user instead.
Open the file /etc/pam.d/gdm in an editor. Find line that reads as follows:
auth required pam_succeed_if.so user != root quiet
Remove or comment out line by prefixing #.
# auth required pam_succeed_if.so user != root quiet
Restart the system