問題描述：
剛在新的Centos上安裝Docker后，運行 docker run hello-world 報錯 Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
解決辦法：
[docker@izwtbz ~]# systemctl daemon-reload
[docker@izwtbz ~]# sudo service docker restart
[docker@izwtbz ~]# sudo service docker status
此時你可以看到：
Active: active (running)
[docker@izwtbz ~]# sudo docker run hello-world