title: How to run mongo db as service using non-default dbpath?
body: <p>When i try to start a service I get</p>
  
  <pre><code>~$ sudo service mongodb start
  mongodb start/running, process 20221
  </code></pre>
  
  <p>but it doesn't really start 
      ~$ sudo service mongodb status
      mongodb stop/waiting</p>
  
  <p>it's probably because my dbpath is NOT default
  so how to start a m service using non-default dbpath</p>