Ubuntu is 1st installed with the “root” user (or admin) disabled. It comes this way for security reasons: ie: so you don’t accidentally delete needed files, to protect you from your own stupidity.  Most people use the terminal to get their admin work done, but this can be difficult for someone new to Ubuntu. Now most people as well as I do not recommend logging in as the root user, sometimes it is just easier. So to do this you will need to go to System-> Administration -> Login Window, then the Security tab and tick “Allow local system administrator login”

Now go to System-> Administration -> Users & Groups, select root and click Properties and change the root password

Then logout and login as:
user: root
pass: Whatever you set it to

Filed under: Linux