title: How to pull from GitLab's Docker Registry in .gitlab-ci.yml?
body: <p>I recently switched on GitLab's Docker Registry feature and it works quite well on my desktop. The next step for us is to use the registry when building our software via GitLab CI. Instead of build a docker image, which is described in various ways in the documentation and on several medium.com posts which the official twitter account mentions, I can not find a way to pull our own images from GitLab's registry.</p>
  
  <p>If we specify an image from the registry via the image directive in <code>.gitlab-ci.yml</code> we get an authorization error (I expected that the worker perhaps authorize themselves transparently, but this is not the case):</p>
  
  <pre><code>Running with gitlab-ci-multi-runner 1.4.1 (fae8f18)
  Using Docker executor with image registry.host.tld/NAMESPACE/PROJECT:latest ...
  Pulling docker image registry.host.tld/NAMESPACE/PROJECT:latest ...
  ERROR: Build failed (system failure): API error (500): Get https://registry.host.tld/v2/NAMESPACE/PROJECT/manifests/latest: error parsing HTTP 403 response body: no error details found in HTTP response body: "{\"message\":\"forbidden\",\"status\":\"error\",\"http_status\":403}"
  </code></pre>
  
  <p>So someone on the worker should call docker login. Two problems with that:</p>
  
  <ol>
  <li>We authenticate our users via LDAP. Should we really create a static user just for the CI server?</li>
  <li>We have quite a few worker running here. That's a lot of work to SSH'd into every single one.</li>
  </ol>
  
  <p>Do I have overlooked something very obvious or should I go the route of docker login on every worker node?</p>
  
  <p>We run GitLab 8.10.6.</p>