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

问题描述：

刚在新的Centos上安装Docker后，运行 docker run hello-world 报错 Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

解决办法：

[docker@izwtbz ~]# systemctl daemon-reload

[docker@izwtbz ~]# sudo service docker restart

[docker@izwtbz ~]# sudo service docker status 

此时你可以看到：
Active: active (running)

[docker@izwtbz ~]# sudo docker run hello-world