Originally Posted by art3m
You can login as root to install or do anything that requires root privileges by typing this in the terminal:
[user@localhost ] su root
you can login as whatever user you like w/ su command "su user" and then enter pass for that user hope that helps!
While that technically works, it's not optimal. Without a - you do not invoke a full login shell, so paths like /usr/sbin would not be provided, making many commands not run by default. There's also no point providing "root" as that is default. Furthermore, sudo is still generally a preferred tool to use over su, especially on ubuntu.