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

安装Docker-CE,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
$ systemctl daemon-reload
$ sudo service docker restart
$ sudo service docker status (should see active (running))
$ sudo docker run hello-world

systemctl: command not found

apt-get install --reinstall systemd