Why can't I login with Glish?
I installed Gnome Desktop on Debian 9 with the command `apt-get install task-gnome-desktop`. I only have a root user installed. I can login to Lish and via ssh as root, however when I try to login with Glish, it always responds with "Sorry, that didn't work. Please try again.".
For security, gdm does not allow root logins. It is recommended that you add an a limited user account with which to login.
If you must use root as a login for your graphical desktop, you can edit the
/etc/pam.d/gdm-password file and comment out the line that says:
auth required pam_succeed_if.so user != root quiet_success
Once you save the file, the preference will be active immediately, so you will not need to reboot or restart your desktop.