docker启动问题
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
如果报出如上错误，说明没有启动docker，需要systemctl start docker
Job for docker.service failed because the control process exited with error code. See "systemctl status docker.service" and "journalctl -xe" for details
如果执行systemctl start docker的时候，又报了新的如上错误，说明SELinux不支持此内核上的overlay2图形驱动程序，禁用selinux即可。vim /etc/sysconfig/docker
直接在enabled后面加上=false即可，然后启动docker