title: Docker service start failed
body: <p>I have a CentOS 7.2 VM with Docker installed. Docker service and Docker container worked normally previously. But when I tried to pull a docker image, the VM was shutdown abruptly. After I restarted the VM, the Docker service could not be started:</p>
  
  <pre><code>[root@AY13091717064020986bZ ~]# service docker start
  Redirecting to /bin/systemctl start  docker.service
  Job for docker.service failed because the control process exited with error code. See "systemctl status docker.service" and "journalctl -xe" for details.
  </code></pre>
  
  <p><code>systemctl status docker.service</code> output:</p>
  
  <pre><code>[root@AY13091717064020986bZ ~]# systemctl status docker.service
  ● docker.service - Docker Application Container Engine
     Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)
     Active: failed (Result: exit-code) since Tue 2016-08-23 19:11:19 CST; 13min ago
       Docs: http://docs.docker.com
    Process: 1404 ExecStart=/usr/bin/docker-current daemon --exec-opt native.cgroupdriver=systemd $OPTIONS $DOCKER_STORAGE_OPTIONS $DOCKER_NETWORK_OPTIONS $ADD_REGISTRY $BLOCK_REGISTRY $INSECURE_REGISTRY (code=exited, status=1/FAILURE)
   Main PID: 1404 (code=exited, status=1/FAILURE)
  
  Aug 23 19:11:17 AY13091717064020986bZ systemd[1]: Starting Docker Application Container Engine...
  Aug 23 19:11:19 AY13091717064020986bZ docker-current[1404]: time="2016-08-23T19:11:19.448828158+08:00" level=warning msg="devmapper: Usage of loopback devices is strongly discou...v section."
  Aug 23 19:11:19 AY13091717064020986bZ docker-current[1404]: time="2016-08-23T19:11:19.511103592+08:00" level=error msg="[graphdriver] prior storage driver \"devicemapper\" faile...t status 2"
  Aug 23 19:11:19 AY13091717064020986bZ docker-current[1404]: time="2016-08-23T19:11:19.511196844+08:00" level=fatal msg="Error starting daemon: error initializing graphdriver: de...t status 2"
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: Failed to start Docker Application Container Engine.
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: Unit docker.service entered failed state.
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: docker.service failed.
  Hint: Some lines were ellipsized, use -l to show in full.
  </code></pre>
  
  <p>"<code>journalctl -xe</code>" output:</p>
  
  <pre><code>[root@AY13091717064020986bZ ~]# journalctl -xe
  Aug 23 19:11:19 AY13091717064020986bZ kernel: device-mapper: block manager: btree_node validator check failed for block 146
  Aug 23 19:11:19 AY13091717064020986bZ kernel: device-mapper: btree spine: node_check failed: csum 1600702373 != wanted 1600827965
  Aug 23 19:11:19 AY13091717064020986bZ kernel: device-mapper: block manager: btree_node validator check failed for block 146
  Aug 23 19:11:19 AY13091717064020986bZ kernel: Buffer I/O error on device dm-1, logical block 2621424
  Aug 23 19:11:19 AY13091717064020986bZ docker-current[1404]: time="2016-08-23T19:11:19.511103592+08:00" level=error msg="[graphdriver] prior storage driver \"devicemapper\" failed: devmapper:
  Aug 23 19:11:19 AY13091717064020986bZ docker-current[1404]: time="2016-08-23T19:11:19.511196844+08:00" level=fatal msg="Error starting daemon: error initializing graphdriver: devmapper: Base
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: Failed to start Docker Application Container Engine.
  -- Subject: Unit docker.service has failed
  -- Defined-By: systemd
  -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
  --
  -- Unit docker.service has failed.
  --
  -- The result is failed.
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: Unit docker.service entered failed state.
  Aug 23 19:11:19 AY13091717064020986bZ systemd[1]: docker.service failed.
  Aug 23 19:11:19 AY13091717064020986bZ polkitd[1014]: Unregistered Authentication Agent for unix-process:1370:16052 (system bus name :1.22, object path /org/freedesktop/PolicyKit1/Authenticati
  Aug 23 19:23:43 AY13091717064020986bZ systemd[1]: Starting Cleanup of Temporary Directories...
  -- Subject: Unit systemd-tmpfiles-clean.service has begun start-up
  -- Defined-By: systemd
  -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
  --
  -- Unit systemd-tmpfiles-clean.service has begun starting up.
  Aug 23 19:23:43 AY13091717064020986bZ systemd[1]: Started Cleanup of Temporary Directories.
  -- Subject: Unit systemd-tmpfiles-clean.service has finished start-up
  -- Defined-By: systemd
  -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
  --
  -- Unit systemd-tmpfiles-clean.service has finished starting up.
  --
  -- The start-up result is done.
  </code></pre>
  
  <p>Docker version:</p>
  
  <pre><code>[root@AY13091717064020986bZ ~]# docker version
  Client:
   Version:         1.10.3
   API version:     1.22
   Package version: docker-common-1.10.3-46.el7.centos.10.x86_64
   Go version:      go1.6.3
   Git commit:      d381c64-unsupported
   Built:           Thu Aug  4 13:21:17 2016
   OS/Arch:         linux/amd64
  Cannot connect to the Docker daemon. Is the docker daemon running on this host?
  </code></pre>
  
  <p>Linux kernel version:</p>
  
  <pre><code>[root@AY13091717064020986bZ ~]# uname -a
  Linux AY13091717064020986bZ 3.10.0-327.el7.x86_64 #1 SMP Thu Nov 19 22:10:57 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
  [root@AY13091717064020986bZ ~]#
  </code></pre>
  
  <p>CentOS version:</p>
  
  <pre><code>[root@AY13091717064020986bZ ~]# lsb_release -a
  LSB Version:    :core-4.1-amd64:core-4.1-noarch
  Distributor ID:    CentOS
  Description:    CentOS Linux release 7.2.1511 (Core)
  Release:    7.2.1511
  Codename:    Core
  [root@AY13091717064020986bZ ~]#
  </code></pre>