How to enable root user in Ubuntu

The root user in Ubuntu is disabled by default because his password is not set. But if you'd like to use root user by some reason, enable it like follows.

1) Set root password

sysstec@ubuntu:~$ sudo passwd root

Enter new UNIX password: # set root password

Retype new UNIX password: # confirm

passwd: password updated successfully
sysstec@ubuntu:~$ su -

Password: # root password

root@ubuntu:~# # just switched

The examples on this site show as a root user from now. If you use sudo, add "sudo" at the head of commands.

2) If you enable root, limit users to switch to root.

root@ubuntu:~# vi /etc/pam.d/su # line 15: uncomment and add a group that can switch to root

auth   required   pam_wheel.so   group=adm

root@ubuntu:~# usermod -G adm sysstec