title: Create Dockerfile interactive?
body: <p>If you look at dockerfiles the often contains lines like this:</p>
  
  <pre><code>sed 's/main$/main universe/' -i /etc/apt/sources.list
  </code></pre>
  
  <p>I think it is difficult to set up things like this.</p>
  
  <p>Is it possible to launch a default OS image, then enter it interactive with a shell, do some modifications, and then print out the diff (filesystem diff)?</p>
  
  <p>The diff should be used as the dockerfile to recreating the image.</p>
  
  <p>But maybe I am missing something, since I am new to docker.</p>