Enable root user on ubuntu

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

[1] Set root password
lucid@ubuntu:~$ sudo passwd root
Enter new UNIX password:# set root password
Retype new UNIX password:# verify
passwd: password updated successfully
lucid@ubuntu:~$ su -
Password:# root password
root@ubuntu:~## just switched to root
* 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 roo, 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:~# vi /etc/group

# line 5: add users you allow to switch to root
adm:x:4:lucid

From (server-world)