title: Usage of loopback devices is strongly discouraged for production use
body: <p>I want to test docker in my CentOS 7.1 box, I got this warning:</p>
  
  <pre><code>[root@docker1 ~]# docker run busybox /bin/echo Hello Docker
  Usage of loopback devices is strongly discouraged for production use. Either use `--storage-opt dm.thinpooldev` or use `--storage-opt dm.no_warn_on_loop_devices=true` to suppress this warning.
  Hello Docker
  </code></pre>
  
  <p>I want to know the reason and how to suppress this warning.</p>
  
  <p>The CentOS instance is running in virtualbox created by vagrant.</p>