title: Using env-file in a sibling docker container
body: <p>I'm trying to run a container in mesos, not that that really matters. The task runner will attempt to spawn a sibling container to run my task but fails because I use <code>--env-file</code>.</p>
  
  <p>I'm attempting to use a file from the host much like mounting volumes. In fact, I'd expect <code>--env-file</code> to work like <code>-v</code> does.</p>
  
  <p>Anyway, the command that mesos is running can be boiled down to this:</p>
  
  <pre><code>docker -H unix:///var/run/docker.sock run --net host -v myvol/mychildvol:/myvol --env-file /etc/envfile --name mesos-task
  </code></pre>
  
  <p>Remove <code>--env-file</code> from this and it works</p>
  
  <p>Importantly /etc/envfile exists on the host running dockerd but not in the mesos-slave container.</p>