[MrThoughtful]

Where does it pull the Debian image from?

I would think the Docker infrastructure is financed by Docker Inc as a marketing tool for their paid services? Are they ok when other software utilizes it?

[FireInsight]

On my system it asks between a few different public registries, and dockerhub/docker.io is one of the choices.

t's all public infrastructure for hosting container images, I don't think Docker-the-company minds other software interfacing with it. After all, they get to call them 'Docker images', 'Dockerfiles', and put their branding everywhere. At this point

[natebc]

By default it uses whatever is in registries.conf for unqualified-search-registries. You can specify in the fully qualified image name if you'd like.

I can't speak to what Docker Inc. is okay with or not.