此问题是因为Docker安装后未启动所致，执行以下命令启动docker：
systemctl start docker.service
具体日志如下：
Connecting to 172.16.10.217:22... Connection established. To escape to local shell, press ‘Ctrl+Alt+]‘. Last login: Fri Aug 24 17:35:46 2018 [root@localhost ~]# docker ps Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running? [root@localhost ~]# systemctl start docker.service [root@localhost ~]# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES [root@localhost ~]# docker images REPOSITORY TAG IMAGE ID CREATED SIZE [root@localhost ~]#
以上显示已经成功启动。
原文：https://www.cnblogs.com/boonya/p/9531173.html