Docker on Ubuntu: http:///var/run/docker.sock/v1.18/containers/json: dial unix /var/run/docker.sock: permission denied
after installing 1.12.3 on Ubuntu 16.04, the permission denied issue came up. after trying the docker group settings without any luck, the only thing left was to actually chmod the socket.
chmod 777 /var/run/docker.sock
and everything works
probably not the wisest thing to do and you can try chmod'ing with more restrictions, but after hours of google and frustration, it works.