Along my own journey of demystification I made a few toy container image registries over the years that generated and served container images from nothing but the URL itself:

https://ko.kontain.me builds a go application on demand and serves it atop a minimal base image

https://apko.kontain.me builds a base image containing packages listed in the URL, again on demand.

The latest addition, https://git.kontain.me serves an image with the specified git repo already checked out in the image.

None of these should be used for anything serious but they were fun to make and play with. :)

random.kontain.me has been uncharacteristically useful in debugging image caching scenarios.

We already have image builders for stuff like Talos Linux and Incus OS. This is not out of the realm of possibility.

this sounds interesting; for e.g., was wondering the other day if we could build images without actually pulling base images.. everytime we compile, we copy artifact(s) onto a multi-hundred MB base image which definitely doesn't need to be pulled everytime.

What are the limitations of `docker build`?

Is "build" being used here in the sense of assembling pre-existing layers into an image? What would be the purpose of that?