[ubuntu] mysql installation doesn't ask for root password

I'm installing MySQL server on 12.04 and it doesn't ask for a root password. Which is awkward because I can't login and do anything.

I've read the instructions for changing the root password in Linux, but it requires me to login as the mysql user, which I can't do because I don't know the password.

I've uninstalled and reinstalled many times and it never asks for a password when I'm installing.

How do I get the thing working?

Thanks