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

应该是docker异常关闭导致无法启动。
步骤1 参考《 https://www.cnblogs.com/langgeligelang/p/14607658.html 》
执行
systemctl daemon-reload
systemctl restart docker
如果失败，提示 Authorization not available. Check if polkit service is running or see debug message for more information。执行步骤2
步骤2 参考< https://blog.csdn.net/weixin_46398647/article/details/129797875>
sudo yum remove polkit
sudo yum install polkit
systemctl daemon-reload
systemctl restart docker
发现问题解决。
以后关闭虚拟机，先关闭docker。