centos ERROR: Couldn't connect to Docker daemon at http+docker://localhost - is it running?

ERROR: Couldn't connect to Docker daemon at http+docker://localhost - is it running?

 

主要原因是docker不是系统服务方式启动。

解决方法：

1、启动docker服务

service docker start
2、生成自启动服务

systemctl enable docker.service
3、查看服务状态，Active状态为：active（running）

systemctl status docker.service