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

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

docker version
Client: Docker Engine - Community
 Version:           20.10.12
 API version:       1.41
 Go version:        go1.16.12
 Git commit:        e91ed57
 Built:             Mon Dec 13 11:45:33 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

root@ubuntu:/etc/docker# cd /etc/docker
root@ubuntu:/etc/docker# ls
daemon.json  key.json

解决办法：
root@ubuntu:/etc/docker# vim daemon.json

{
 "registry-mirrors": ["https://registry.docker-cn.com"]
}

：wq

root@ubuntu:/etc/docker# systemctl restart docker.service
再使用docker命令时，就没有问题了
希望这个方法对你们有用
最后，我是得益于这位博主的文章来写的，感谢~

https://blog.csdn.net/weixin_45496075/article/details/109123709
各位朋友还是设置docker开机自启吧