title: Docker in Docker permissions error
body: <p>I have a docker in docker setup for CI. Essentially, the machine has a jenkins CI server on it that uses the same machines docker socket to create nodes for CI. </p>
  
  <p>This was working great until I recently updated docker. I've identified the issue, but I can't seem to figure out the right magic to get it working.</p>
  
  <pre><code>host $ docker exec -it myjenkins bash
  jenkins@container $ docker ps
  Got permission denied while trying to connect to the Docker daemon 
  socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.26/containers/json: dial unix /var/run/docker.sock: connect: permission denied
  
  host $ docker exec -it -u root -it myjenkins bash
  root@container $ docker ps 
  ... docker ps from host container yay! ...
  </code></pre>
  
  <p>So here's what I surmise. I have access to the host docker socket from within the container, but I can't seem to give permission to the jenkins user.</p>
  
  <p>I've added the docker group, and also added the jenkins user to the docker group. But I still get the same error. I've restarted a whack of times so, I'm kind of at a loss for what to do next. </p>
  
  <p>Is there a way to force permissions for a user on a particular socket?</p>