Reuse inherited image's CMD or ENTRYPOINT

Question

How can I include my own shell script CMD on container start/restart/attach, without removing the CMD used by an inherited image?

I am usin

Answer 1

If the base image is not yours, you unfortunately have to call the parent command manually.

If you own the parent image, you can try what the people at camptocamp suggest here.

They basically use a generic script as an entry point that calls run-parts on a directory. What that does is run all scripts in that directory in lexicographic order. So when you extend an image, you just have to put your new scripts in that same folder.

However, that means you'll have to maintain order by prefixing your scripts which could potentially get out of hand. (Imagine the parent image decides to add a new script later...).

Anyway, that could work.

Update #1

There is a long discussion on this docker compose issue about provisioning after container run. One suggestion is to wrap you docker run or compose command in a shell script and then run docker exec on your other commands.

If you'd like to use that approach, you basically keep the parent CMD as the run command and you place yours as a docker exec after your docker run.