How to set root password on Amazon EC2 instance?

Question

At first, I SSHed into an instance as 'ubuntu' user, typed 'sudo -s', and it didn't ask me for the root password. Then I entered 'passwd' as 'root' user and typed twice the new password, and confirmed them.

But the next time I SSH into this instance as 'ubuntu' user, type 'sudo -s', and it still doesn't ask me for any password!

Am I missing something?

The instance runs Ubuntu 8.04(Hardy).

Solution

Have a look at /etc/sudoers. There is defined whether you need a password (and if root's or your own one) for the diverse invocations of sudo.