title: Unable to use sudo on OSX, getting sudo: unknown uid 501: who are you?
body: <p>When I type <code>sudo &lt;command&gt;</code> in terminal I get <code>sudo: unknown uid 501: who are you?</code> and when I type <code>su</code> I get <code>su: who are you?</code></p>
  
  <p>I think I must have changed super user permissions somehow on my personal machine. I'm not able to use sudo commands now, and I've not been able to find any helpful solutions. Do I have to do something with my <code>/etc/passwd</code> file? Can I even modify that?</p>