title: Run Different Linux OS in Docker Container?
body: <p>Have been trying to learn Docker and one thing that puzzles me is how a different flavour of Linux (to the host OS) actually runs in the Docker container.</p>
  
  <p>If we assume my Docker host is running RedHat and I start a container from an Ubuntu image then are the following true?:</p>
  
  <ul>
  <li>logically speaking, if the Ubuntu image footprint is around 550MB then will the Docker Daemon actually download (from an image registry) 550MB worth of Ubuntu image in order to create the Container?</li>
  <li>is the instance of Ubuntu running in the container essentially no different than if I had downloaded and installed the same version manually?</li>
  </ul>
  
  <p>I'm aware that the Docker container shares the same kernel used by the host OS and that one of the fundamental points of Docker was its efficiency gains of the container using the underlying OS. So Im a bit confused about what actually happens when you start a Container created from a different Linux version than the host.</p>