I have encountered this problem when I try to run your docker using Ubuntu 14.04.
Does it mean I need to install something else?
bshang2@mechatronicslab-OptiPlex-990:~$ sudo xhost +local:`docker ps -aqf "name=erle-sim"`
Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.30/containers/json?all=1&filters=%7B%22name%22%3A%7B%22erle-sim%22%3Atrue%7D%7D: dial unix /var/run/docker.sock: connect: permission denied
non-network local connections being added to access control list
I have posted this on your Github, but I did not get reply.