Run a script the first time an image is run.

[jacobalberty]

This is a feature request that may be a bit more than dumb-init is intended to contain but it is something I've been looking for in a docker init.

The idea being if there's initial setup (perhaps generating a random password) it should be run when the container is initialized and not when the image is created. It would be nice to have a clean way of performing that task the first time a container is run and then not do it again after.

[asottile]

We've done this in the following way:

CMD ["dumb-init", "./setup.sh"]

#!/usr/bin/env bash

# Run some runtime setup code
echo hi > /etc/app.conf

# exec the application
exec python app.py

This'll allow you to end up with a process tree that looks like

dumb-init
+--- python app.py

and give you your setup code

[jacobalberty]

I mean for a one time run though, runs the first time the container is initialized then never runs again, sort of a post-ininitialization hook. Trying to find a clean way to accomplish it.

[asottile]

Would this be run once per box or once per everything (I don't think the second is possible, and the first you'd need to store some state on disk probably?)