title: How to set root password on Amazon EC2 instance?
body: <p>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.</p>
  
  <p>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!</p>
  
  <p>Am I missing something?</p>
  
  <p>The instance runs Ubuntu 8.04(Hardy).</p>