title: MySQL: why are there multiple root users?
body: <p>On a clean install of MySQL (version: 5.5.49-0ubuntu0.14.04.1) running <code>SELECT User FROM mysql.user;</code> returns</p>
  
  <pre><code>+------------------+
  | User             |
  +------------------+
  | root             |
  | root             |
  | debian-sys-maint |
  | root             |
  +------------------+
  4 rows in set (0.00 sec)
  </code></pre>
  
  <p>Can someone please tell me why there are 3 root users? </p>