title: Docker image size not matching the container size after a commit
body: <p>Recently I created a docker container from a centos base image which ran a jboss. Originally I had installed the jdk (and committed) which made the container bulky (about 850M). Later, I uninstalled jdk and installed jre. From inside the container a </p>
  
  <pre><code>du -xsh /
  </code></pre>
  
  <p>shows only 440M. But after committing the changes to the image it still shows 711M. Should the image size not match (or be close to) the container's <em>du</em>? Or while committing, does docker keep adding to the old ones (like an SCM)?</p>
  
  <p>Thanks</p>