title: Docker service does not start anymore after Ubuntu 18.04 update: dm_task_run failed / no such device storage-driver=overlay2
body: <p>After I triggered an unattended-upgrade on Ubuntu 18.04 (currently 18.04.5) and rebooted the server my docker service does not start anymore. So I tried to run it manually with sudo dockerd but got the following errors:</p>
  <blockquote>
  <p>failed to mount overlay: no such device storage-driver=overlay2 docker
  failed to start daemon: error initializing graphdriver: driver not
  supported</p>
  </blockquote>
  <p>After fiddling around with various suggestions (incl. the obligatory reboot x times) I gave up and uninstalled docker (incl. deleting usr/lib/docker) to reinstall the newest version. But this only changed the error message to:</p>
  <blockquote>
  <p>failed to start daemon: error initializing graphdriver: devicemapper:
  Error running deviceCreate (CreatePool) dm_task_run failed</p>
  </blockquote>
  <p>I have more than enough disk space and already tried to delete the /usr/lib/docker folder (which btw. doesn't have an overlay2 folder which my previous installation at least had), but those suggestions didn't work. If I force --storage-driver=overlay2 I get the old &quot;failed to mount overlay:...&quot; from above.</p>
  <p>I am now totally clueless how to solve this problem. Any ideas?</p>
  <p>Edit: It seems that all the dm_* errors shouldn't be my problem, since they come from devicemapper which shouldn't be used. Instead the overlay2 stuff should work. So it all boils down to: Why does overlay2 not work (anymore?) on my machine?</p>
  <p>Current versions:</p>
  <ul>
  <li>Ubuntu 18.04.5 LTS (GNU/Linux 4.15.0-106-generic x86_64)</li>
  <li>Docker version 19.03.12, build 48a66213fe</li>
  </ul>
  <p>Full error message:</p>
  <blockquote>
  <p>INFO[2020-09-10T12:38:41.720023381+02:00] Starting up
  INFO[2020-09-10T12:38:41.721017055+02:00] detected 127.0.0.53
  nameserver, assuming systemd-resolved, so using resolv.conf:
  /run/systemd/resolve/resolv.conf
  INFO[2020-09-10T12:38:41.723286420+02:00] parsed scheme: &quot;unix&quot;<br />
  module=grpc INFO[2020-09-10T12:38:41.723397263+02:00] scheme &quot;unix&quot;
  not registered, fallback to default scheme  module=grpc
  INFO[2020-09-10T12:38:41.723468274+02:00] ccResolverWrapper: sending
  update to cc: {[{unix:///run/containerd/containerd.sock 0  }]
  }  module=grpc INFO[2020-09-10T12:38:41.723493045+02:00]
  ClientConn switching balancer to &quot;pick_first&quot;  module=grpc
  INFO[2020-09-10T12:38:41.727552254+02:00] parsed scheme: &quot;unix&quot;<br />
  module=grpc INFO[2020-09-10T12:38:41.727619515+02:00] scheme &quot;unix&quot;
  not registered, fallback to default scheme  module=grpc
  INFO[2020-09-10T12:38:41.727666336+02:00] ccResolverWrapper: sending
  update to cc: {[{unix:///run/containerd/containerd.sock 0  }]
  }  module=grpc INFO[2020-09-10T12:38:41.727698707+02:00]
  ClientConn switching balancer to &quot;pick_first&quot;  module=grpc
  ERRO[2020-09-10T12:38:41.845132923+02:00] [graphdriver] prior storage
  driver devicemapper failed: devicemapper: Error running deviceCreate
  (CreatePool) dm_task_run failed failed to start daemon: error
  initializing graphdriver: devicemapper: Error running deviceCreate
  (CreatePool) dm_task_run failed</p>
  </blockquote>