title: Docker Cleanup - Can I delete old directories under /var/lib/docker/containers
body: <p>I have 16 docker containers running in my system which stores a lot of data under<code>/var/lib/docker/overlay2/&lt;id&gt;</code>(around 30 GB per-directory.. Total 30*16 GB). Primarily space is consumed by <code>diff</code> and <code>merged</code> directories inside it.</p>
  <p>Every time I do a <code>docker-compose down</code> followed by  <code>docker-compose up</code>, it creates another set of 16 directories and starts storing data under that. <strong>But it does not clean up old overlay2 directories. This leads to a space crunch</strong></p>
  <ol>
  <li>Please let me know if I can do rm -rf /var/lib/docker/overlay2/
  of old directories or how I can free up space.</li>
  <li>Do I need to wait for a couple of hours after <code>docker-compose down</code> to
  reclaim space?</li>
  </ol>
  <p>Note: I did a <code>docker system prune -a</code> also.</p>