root login

To allow log in as root into GNOME, you need to make some changes in the GDM configuration file located at /etc/gdm3/custom.conf 

#  cp /etc/gdm3/custom.conf /etc/gdm3/custom.conf.ORG

#  vi /etc/gdm3/custom.conf

# [And add the following line to allow the root login:] 

AllowRoot=true         

#  vi /etc/pam.d/gdm-password

# auth   required        pam_succeed_if.so user != root quiet_success 

#  reboot