Issue: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.35/containers/json: dial unix /var/run/docker.sock: connect: permission denied
Solutions:
The errors messages tell you that your current user can't access the docker engine, since you lack of the permission to access the unix socket to communicate with the engine.
For temp solution: you can "sudo the command" to get the permission as root.
It's recommended to fix the issue by adding the current user to the "docker" group. then completely log out and log back in.
sudo usermod -a -G docker $USER
轉自：https://techoverflow.net/2017/03/01/solving-docker-permission-denied-while-trying-to-connect-to-the-docker-daemon-socket/