最近发现某台机器上的Docker服务无法开启，报如下错误：
[root@localhost ~]# docker ps -a
Cannot connect to the Docker daemon. Is 'docker -d' running on this host?
[root@localhost ~]# service docker restart
Redirecting to /bin/systemctl restart docker.service
Job for docker.service failed. See 'systemctl status docker.service' and 'journalctl -xn' for details.
没找到对应的解决方法，只能进行重装了。以下附上Centos7下卸载docker的命令：
[root@localhost ~]# yum list installed | grep docker
Repodata is over weeks old. Install yum-cron? Or run: yum makecache fast
docker.x86_64 1.7.-.el7.centos @extras
docker-selinux.x86_64 1.7.-.el7.centos @extras
[root@localhost ~]# yum -y remove docker.x86_64
[root@localhost ~]# yum -y remove docker-selinux.x86_64