Docker - entrypoint.sh and alternatives and a bit of gosu & exec

Entrypoint scripts can be used to bootstrap a container and then hand off control to a long-running process.   (maybe using exec+gosu)
https://success.docker.com/article/use-a-script-to-initialize-stateful-container-data

(the exec Bash command can be used so that the final running application becomes the container’s PID 1. This allows the application to receive any Unix signals sent to the container.  exec replaces the shell with a given program (executing it, Not as new process))

(The core use case for gosu is to step down from root to a non-privileged user during container startup (specifically in the ENTRYPOINT, usually) (gosu alternatives)



An alternative:
These guys execute "run-parts" on a startup folder.
That way containers derived from a base container can just dump other startup scripts in the that folder.
https://www.camptocamp.com/en/actualite/flexible-docker-entrypoints-scripts/