title: Add a new entrypoint to a docker image
body: <p>Recently, we decided to move one of our services to docker container. The service is product of another company and they have provided us the docker image. However, we need to do some extra configuration steps in the container entrypoint. </p>
  
  <p>The first thing I tried, was to create a DockerFile from the base image and then add commands to do the extra steps, like this:</p>
  
  <pre><code>From baseimage:tag 
  RUN chmod a+w /path/to/entrypoint_creates_this_file
  </code></pre>
  
  <p>But, it failed, because these extra steps must be run after running the base container entrypoint.</p>
  
  <p>Is there any way to <strong>extend</strong> entrypoint of a base image? if not, what is the correct way to do this?</p>
  
  <p>Thanks</p>