By default in Ubuntu Linux operating system the root user comes in disabled state for security reason and you can’t login using root. The reason behind this is there is risk of any by mistake changes of any important files or configurations, someone can misuse of this feature and so on. Hence in Ubuntu to do any administrative changes or important changes you can use sudo command.
sudo passwd root sudo passwd -u root sudo nano /etc/gdm3/custom.conf ===== [security] AllowRoot=true ===== sudo nano /etc/pam.d/gdm-password ===== # auth required pam_succeed_if.so user != root quiet_success ===== sudo nano /root/.profile ===== # ~/.profile: executed by Bourne-compatible login shells. if [ "$BASH" ]; then if [ -f ~/.bashrc ]; then . ~/.bashrc fi fi if `tty -s`; then mesg n fi =====