sudo nano /etc/gdm3/custom.conf
Inside the GDM configuration file, we need to add the
AllowRoot=true line. After you have made this change, you can save and exit the file.
sudo nano /etc/pam.d/gdm-password
Inside of the PAM authentication daemon file, comment out the following line, which denies root access to the graphical user interface, with a pound sign
#. You can save your changes and exit this file when done.
auth required pam_succeed_if.so user != root quiet_success