CentOS 7 Docker 無法連線 Docker daemon？

訊息內容:
[root@localhost ~]# docker search mysql
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

解決方式:
重啟docker service
[root@localhost ~]# systemctl restart docker

參考資料:
https://blog.yowko.com/cannot-connect-docker-daemon/