title: How to use wkhtmltopdf with Docker
body: <p>When I use wkhtmltopdf (version 0.12.2.4, installed via apt-get) within a Docker container it fails with</p>
  
  <pre><code>QXcbConnection: Could not connect to display
  </code></pre>
  
  <p>(When I set the environment variable <code>DISPLAY=unix0</code>, I get <code>QXcbConnection: Could not connect to display unix0</code> which makes sense as no Xserver seems to be installed)</p>
  
  <p>There seems to be a headless version (<a href="https://stackoverflow.com/a/32551105/562769">source</a>) and I thought that would mean that I don't need an Xserver.</p>
  
  <p>(<code>xvfb</code> seems to be another option, but I'm not sure how to run it / what to install)</p>
  
  <p><strong>How can I run wkhtmltopdf in a Docker container, if I can't change the base image to <code>openlabs/docker-wkhtmltopdf</code>?</strong></p>