Docker may give you the permission deniend error on Linux:
$ docker run busybox date
2015/08/01 15:37:42 Post
http:///var/run/docker.sock/v1.12/containers/create: dial unix
/var/run/docker.sock: permission denied
Run the following command and log out to fix the above error.
sudo usermod -a -G docker ${USER}
References