title: Mounted volume is empty inside container
body: <p>I've got a <code>docker-compose.yml</code> like this:</p>
  
  <pre><code>db:
    image: mongo:latest
    ports:
      - "27017:27017"
  server:
    image: artificial/docker-sails:stable-pm2
    command: sails lift
    volumes:
      - server/:/server
    ports:
      - "1337:1337"
    links:
      - db
  </code></pre>
  
  <p><code>server/</code> is relative to the folder of the <code>docker-compose.yml</code> file. However when I <code>docker exec -it CONTAINERID /bin/bash</code> and check <code>/server</code> it is empty.</p>
  
  <p><strong>What am I doing wrong?</strong> </p>