title: Why docker has ability to run different linux distribution?
body: <p>We can use docker to pull different images. And these images are different linux distribution.
  But no matter which linux distro docker is running on, docker can run these different linux distribution just like in a virtual machine.</p>
  
  <p>I know docker uses <a href="http://en.wikipedia.org/wiki/Aufs" rel="noreferrer">aufs</a> to control different read-write access level. So it can reuse some file on the host machine. But how can docker run <code>apt-get</code> in a container when my host runs <code>arch linux</code>? Does the image contain the <code>apt-get</code> binary? But different linux distribution have different libs and software version. Even the configuration file are different.How can docker "run" ubuntu in a arch linux?</p>