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dockerboot2docker

How do I modify a startup script in a docker container when it is stopped?

We have a docker container which I run as:

docker run --name myname -e PROPERTY1=VALUE1   -d image/name

Dockerfile used to build the container:

ADD start.sh /
CMD ["/bin/bash","/start.sh"]

Can I edit the file start.sh without rebuilding the container.

My guess is

  • stop the container
  • edit the file
  • start the container.

How do I edit the file when the container is stopped?

Thanks.

Solution

  • You could follow the steps you outlined, but it requires knowing exactly where the container filesystem is on the host and making sure you have the right permissions to modify it. That's not the path I'd suggest.

    Ideally you'd do everything through a Dockerfile so that you have a reproducible way to rebuild the image in the future. You'll want that in six months when packages or dependencies need updating. You already know how to do that, so I'll presume you're looking for a quick hack.

    Quick Hack (Non-reproducible results)

    1. docker run your image to get it going as a container
    2. docker exec -it CONTAINER /bin/bash (or equivalent shell) to get into the running container. Edit your file within the container. Exit (ctrl-D typically).
      • This method of editing means you don't have to find the container's file system on the host or negotiate permissions to edit files there. You're already in and on the file system.
      • But the only copy of the modified file is inside your container, so nobody else can reproduce what you did exactly.
    3. docker commit CONTAINER REPOSITORY:TAG
    4. docker run REPOSITORY:TAG