Also, make sure to try 'docker history'. It preserves the graph of which command created which image....

For example, this is the image I use to automatically update docker's binary downloads:

   $ docker pull shykes/dockerbuilder  # Be patient, it's a big one

   $ docker history shykes/dockerbuilder

   $ docker run -i -t shykes/dockerbuilder /usr/local/bin/dockerbuilder $REVISION $S3_ID $S3_KEY