docker启动失败解决

在使用systemctl start docker启动失败时，使用systemctl status docker.service其报告如下：

docker.service - Docker Application Container Engine
   Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Fri 2018-04-27 02:38:36 EDT; 12s ago
     Docs: http://docs.docker.com
  Process: 2356 ExecStart=/usr/bin/dockerd-current --add-runtime docker-runc=/usr/libexec/docker/docker-runc-current --default-runtime=docker-runc --exec-opt native.cgroupdriver=systemd --userland-proxy-path=/usr/libexec/docker/docker-proxy-current --seccomp-profile=/etc/docker/seccomp.json $OPTIONS $DOCKER_STORAGE_OPTIONS $DOCKER_NETWORK_OPTIONS $ADD_REGISTRY $BLOCK_REGISTRY $INSECURE_REGISTRY $REGISTRIES (code=exited, status=1/FAILURE)
 Main PID: 2356 (code=exited, status=1/FAILURE)

Apr 27 02:38:35 localhost.localdomain systemd[1]: Starting Docker Application Container Engine...
Apr 27 02:38:35 localhost.localdomain dockerd-current[2356]: time="2018-04-27T02:38:35.166869440-04:00" level=warning msg="could not change group /var/run/docker.sock to docker: group docker not found"
Apr 27 02:38:35 localhost.localdomain dockerd-current[2356]: time="2018-04-27T02:38:35.171487584-04:00" level=info msg="libcontainerd: new containerd process, pid: 2361"
Apr 27 02:38:36 localhost.localdomain dockerd-current[2356]: Error starting daemon: SELinux is not supported with the overlay2 graph driver on this kernel. Either boot into a newer kernel or disable selinux in docker (--selinux-enabled=false)
Apr 27 02:38:36 localhost.localdomain systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
Apr 27 02:38:36 localhost.localdomain systemd[1]: Failed to start Docker Application Container Engine.
Apr 27 02:38:36 localhost.localdomain systemd[1]: Unit docker.service entered failed state.
Apr 27 02:38:36 localhost.localdomain systemd[1]: docker.service failed.

截图如下：

此处意思是linux的内核中的SELinux不支持 overlay2 graph driver ，解决方法有两个，要么启动一个新内核，要么就在docker里禁用selinux，–selinux-enabled=false,
解决办法如下：

vi /etc/sysconfig/docker