By default root user account is disabled for login in Ubuntu. Steps mentioned below will allow you to enable the root user and login as root on the OS.
- Login to your account and open Terminal
- sudo passwd root
- Type in the new password for UNIX
sudo gedit /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf
- At the end of the file append
greeter-show-manual-login = true
That’s all, now reboot the system and you can login to root account using manual login.
If you wish to know more options available for the configuration of the login screen you may visit https://wiki.ubuntu.com/LightDM