sudo systemctl status docker -l

gistfile1.txt

● docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Fri 2015-06-05 09:10:46 UTC; 4min 40s ago
     Docs: http://docs.docker.com
  Process: 1089 ExecStart=/usr/bin/docker -d -H fd:// (code=exited, status=1/FAILURE)
 Main PID: 1089 (code=exited, status=1/FAILURE)

Jun 05 09:10:46 scarlet docker[1089]: time="2015-06-05T09:10:46Z" level=info msg="Loading containers: start."
Jun 05 09:10:46 scarlet docker[1089]: time="2015-06-05T09:10:46Z" level=info msg="Loading containers: done."
Jun 05 09:10:46 scarlet docker[1089]: time="2015-06-05T09:10:46Z" level=info msg="docker daemon: 1.6.2 7c8fca2; execdriver: native-0.2; graphdriver: aufs"
Jun 05 09:10:46 scarlet docker[1089]: time="2015-06-05T09:10:46Z" level=info msg="+job acceptconnections()"
Jun 05 09:10:46 scarlet docker[1089]: time="2015-06-05T09:10:46Z" level=info msg="-job acceptconnections() = OK (0)"
Jun 05 09:10:46 scarlet docker[1089]: time="2015-06-05T09:10:46Z" level=info msg="Daemon has completed initialization"
Jun 05 09:10:46 scarlet docker[1089]: time="2015-06-05T09:10:46Z" level=fatal msg="Shutting down due to ServeAPI error: No sockets found"
Jun 05 09:10:46 scarlet systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
Jun 05 09:10:46 scarlet systemd[1]: Unit docker.service entered failed state.
Jun 05 09:10:46 scarlet systemd[1]: docker.service failed.

systemctl status docker.socket should print something like :

● docker.socket - Docker Socket for the API
   Loaded: loaded (/usr/lib/systemd/system/docker.socket; disabled; vendor preset: disabled)
   Active: active (running) since Mon 2015-06-01 08:13:15 CEST; 4 days ago
   Listen: /var/run/docker.sock (Stream)

Jun 01 08:13:15 hokkaido systemd[1]: Starting Docker Socket for the API.
Jun 01 08:13:15 hokkaido systemd[1]: Listening on Docker Socket for the API.