The best way from an Ubuntu install (if I remember right) is not to directly run the "super user" command, but instead to run "sudo <command>" You can do "sudo su" to change to root for an entire session, but it's best to just use sudo on a command by command basis when root access is needed. sudo runs commands at root level, after authenticating using your normal user account. I can't remember how the user management worked in Ubuntu, but OS X calls users with sudo access administrators.