I came across an issue working with Ubuntu where I couldn't access the root user. I understand that the Ubuntu philosophy is that you primarily use a default user and sudo any privileged commands. This is a great philosophy, however the stubbornness in my wants that root user. Fortunately, there was an easy way for me to get this. In order to get access to the root user account, I ran the following command from a terminal session:
sudo passwd root
Once I entered the User password for my current user, the Unix passwd command came up wanting to know the new password for the root user. I entered the password and was all set. Now I can run su from a command prompt whenever I need to get access to the root account. Some would say this is a bad thing, however i don't like being told I cannot access something on my system. this is one of the reasons I don't buy Cd's anymore, and am moving away from Microsoft for everything except work.