Comment by mikepurvis

The ansible-in-containers thing is very much an unsolved problem. Basically right now you have three choices:

- install ansible in-band and run it against localhost (sucks because your playbook is in a final image layer; you might not want Python at all in the container)

- use packer with ansible as your provisioner and a docker container export, see: https://alex.dzyoba.com/blog/packer-for-docker/

- copy a previous stage's root into a subdirectory and then run ansible on that as a chroot, afterward copy the result back to a scratch container's root.

All of these options fall down when you're doing anything long-running though, because they can't work incrementally. As soon as you call ansible (or any other tool), then from Docker's point of view it's now a single step. This is really unfortunate because a Dockerfile is basically just shell invocations, and ansible gives a more structured and declarative-ish way to do shell type things.

I have wondered if a system like Dagger might be able to do a better job with this, basically break up the playbook programmatically into single task sub-playbooks and call each one in its own Dagger task/layer. This would allow ansible to retain most of its benefits while not being as hamstrung by the semantics of the caller. And it would be particularly nice for the case where the container is ultimately being exported to a machine image because then if you've defined everything in ansible you have a built-in story for freshening that deployed system later as the playbook evolves.