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

问题：

[[email protected] docker]# docker-compose stop
ERROR: Couldn't connect to Docker daemon at http+docker://localhost - is it running?

If it's at a non-standard location, specify the URL with the DOCKER_HOST environment variable.

解决如下：

• 如果还没有 docker group 就添加一个

  sudo groupadd docker

• 将用户加入该 group 内

  sudo gpasswd -a ${USER} docker

• 重启 docker 服务

  sudo service docker restart

实例： 

[[email protected] docker]# sudo groupadd docker
groupadd: group 'docker' already exists
[[email protected] docker]# sudo gpasswd -a ${USER} docker
Adding user root to group docker
[[email protected] docker]# sudo service docker restart
Redirecting to /bin/systemctl restart docker.service
[[email protected] docker]#