Docker报错误Cannot connect to the Docker daemon

笔者在执行docker search gitlab命令时，发生如下错误

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

然后再执行docker ps发生如下错误

解决办法：

问题原因是因为docker服务没有启动，所以在相应的/var/run/路径下找不到docker的进程。

[root@localhost gitlab_docer]# cd /var/run/

[root@localhost run]# service docker start

Redirecting to /bin/systemctl start docker.service

[root@localhost run]# systemctl daemon-reload

[root@localhost run]# service docker start