title: fuser returns Cannot Permission denied
body: <p>If I run <code>fuser -n tcp 80</code> on ubuntu 14.0.4 which is running in a docker image, I get:</p>
  
  <pre><code>Cannot stat file /proc/25/fd/0: Permission denied
  Cannot stat file /proc/25/fd/1: Permission denied
  Cannot stat file /proc/25/fd/2: Permission denied
  Cannot stat file /proc/25/fd/3: Permission denied
  Cannot stat file /proc/25/fd/4: Permission denied
  Cannot stat file /proc/25/fd/5: Permission denied
  etc.
  80/tcp:                 24
  </code></pre>
  
  <p>If I run <code>whoami</code> it returns root.</p>
  
  <p>Why can I not run this command?</p>