title: Modifying a docker image that was created from an existing one
body: <p>By following a how-to, I've created a new image based on an existing one.<br />
  I don´t have the original images' Dockerfile and there are things happening when the container starts that
  I can't change - that´s how it seems anyway.</p>
  <p>Is there a way to modify the commands in the Dockerfile of the base image?</p>
  <p>For example the container runs a bash script when it starts, I want to change this.</p>