title: Docker on machine using a ramdisk doesn't work
body: <p>My machine that boots on a ramdisk cannot start a docker container.</p>
  
  <p>For example, running <code>hello-world</code> results in</p>
  
  <pre><code>$ docker run hello-world
  docker: Error response from daemon: OCI runtime create failed: container_linux.go:345: starting container process caused "process_linux.go:430: container init caused \"rootfs_linux.go:109: jailing process inside rootfs caused \\\"pivot_root invalid argument\\\"\"": unknown.
  ERRO[0000] error waiting for container: context canceled
  </code></pre>
  
  <p>Unfortunately, the <code>DOCKER_RAMDISK=true</code> variable does not seem to have an effect. I set it before restarting the docker service with <code>systemctl restart docker</code> but with no effect.
  (I'm on Debian Buster)</p>