title: Are there known security risks in running docker with user namespace disabled?
body: <p>I've been playing with Docker in Ubuntu using DigitalOcean's Dokku image. Everything seems to work fine. Just checking how the installation of docker is done I found that <code>lxc-checkconfig</code> reports <code>User namespace: Disabled</code>.</p>
  
  <p><a href="http://www.boronine.com/2013/12/30/Installing-Docker-on-Debian-Jessie/" rel="nofollow">This tutorial</a> explain that is because the kernel wasn't compiled with <code>CONFIG_USER_NS=y</code> so it can be achieved by recompiling.</p>
  
  <p>Since everything works fine I'm wondering if there's something I missing about this user namespace thing, for instance, a security benefit.</p>
  
  <p>So, why is the functionality added by enabling User Namespace? What risks or known issues are there if I keep it disabled?</p>