title: Is it safe to clean docker/overlay2/
body: <p>I got some docker containers running on <strong>AWS EC2</strong>, the /var/lib/docker/overlay2 folder grows very fast in disk size.</p>
  <p>I'm wondering if it is safe to delete its content?
  or if docker has some kind of command to free up some disk usage.</p>
  <hr />
  <p><strong>UPDATE:</strong></p>
  <p>I actually tried <code>docker system prune -a</code> already, which reclaimed 0Kb.</p>
  <p>Also my /docker/overlay2 disk size is much larger than the output from <code>docker system df</code></p>
  <p>After reading docker documentation and BMitch's answer, I believe it is a stupid idea to touch this folder and I will try other ways to reclaim my disk space.</p>