title: Save data as part of Docker image?
body: <p>I'm trying to create a custom Docker image for Ghost (<a href="https://ghost.org/" rel="nofollow noreferrer">https://ghost.org/</a>) with some themes pre-installed. I pulled the official image (<a href="https://hub.docker.com/_/ghost/" rel="nofollow noreferrer">https://hub.docker.com/_/ghost/</a>) and installed the Uno Zen (<a href="https://github.com/Kikobeats/uno-zen" rel="nofollow noreferrer">https://github.com/Kikobeats/uno-zen</a>) theme as per the instructions - clone into <code>content/themes</code>, run the setup script etc.</p>
  
  <p>I then ran <code>docker commit</code> to push these changes as another layer on the existing Docker image. However, the next time I spin up a container using this image, I do not see the theme files where they should be. It's like none of the changes persisted.</p>
  
  <p>What am I doing wrong?</p>