first thing to do in Ubuntu is to enable the root user (To be like every other Linux distro---and to be true to the legacy of Unix....
Seriously, not having a root user by default is just about the only flaw in my favorite distro.
In a terminal:
sudo passwd root
enter YOUR password at the prompt, and then enter the new password for the root account.
In System ---> Administration, select login screen setup. Under security, click the box to allow root to log in.