title: How to move images of docker in aufs directory to overlay2?
body: <p>I update my kernel of Debian from 3.x to 4.x.<br/>
  Docker storage become overlay2.</p>
  
  <pre><code>ls /var/lib/docker/ 
  containers  image  network  overlay2  plugins  swarm  tmp  trust  volumes
  </code></pre>
  
  <p>old directory structure is </p>
  
  <pre><code>aufs  containers  graph  image  init  linkgraph.db  network  plugins  repositories-aufs  swarm  tmp  tmp-old  trust  volumes
  </code></pre>
  
  <p>My images is in aufs directory, I can not start docker service with old directory. how can I move my images to overlay2?</p>