title: Keeping a X11 application alive, which I can disconnect from and reconnect to afterwards
body: <p>I currently have a tiny, headless (and I certainly want to keep it that way :) ) Linux Virtual Machine set up with Vagrant and VirtualBox which, for testing, I want to run an X11 application (Firefox) whose output comes to Xming on my real machine.  All that's hunky dory, working perfectly, but I'm not happy yet!</p>
  
  <p>What I want to be able to do is do a few setup things, make sure everything's running correctly, then disconnect from the server and let the testing run it's course.  If however something goes wrong, or I want to just check the current status of things (some of the tests may run into hours), I'd like to then hop back onto the server and point the X11 output to my machine again.  But despite a good deal of Google-ing and learning loads about X11 that I didn't know a few hours ago, I can't find anything about choosing where the output of an X11 application goes, except at startup, ie;</p>
  
  <pre><code>DISPLAY=:10 firefox &amp;
  </code></pre>
  
  <p>I had read some random blog post that Xephyr XServer did this (kind of act as an intermediate X11 buffer, which then redirects if you want it to, otherwise just outputs to /dev/null), but I can't find any other reference to it, or anything else doing that.</p>