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How do YOU create your Docker images?
(lemmy.ml)
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this post was submitted on 07 Sep 2023
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Maybe you should read up a bit about how docker works, you seem to misunderstand a lot here.
For example the "various images" are kind of the point of docker. Images are layered, and each layer is its own image, so you might end up with 3 or 4 images despite only building one image.
This is something you can't really prevent. It's just how docker works.
Anyway, you can mount the docker socket into a container, and using that socket you can then build an image within the running container. That's essentially how most ci/cd systems work.
You could maybe look into podman and buildah, as far as I know, these can build images without a running docker daemon. That might be a tad "cleaner", but comes with other problems (like no caching).
I have no problem with Docker creating several images and containers and volumes for building a single-image application. The problem is that it does not clean up afterwards and leaves me with multiple things I don’t need for anything else.
I also don’t care about caching or any “magic” stuff. I just ideally want to run one command (or script doing it for me) to build an image resulting in just this one image without any other traces left. … I just like a clean environment and the build process ideally being self-contained.
But I’ll look into your suggestions, thanks!
I seriously don't understand what leftovers you're talking about.
You essentially have a Dockerfile that describes how you want to build your image, you run docker build with the path of your Dockerfile and the path of the context, and the rest is completely up to you. Docker does not leave that many traces around - only the built images within docker itself, but as I said, that's the point of building them.
You can even export the image into a tar file and run docker prune afterwards, that should only leave the exported tar file.
When I built an image last time there were several unused other images with just hashes as names and two unused volumes, also multiple cache files and other files in the user’s home directory in various subfolders.
It's very possible they weren't unused.
Docker builds their images out of layers, and all the layers are used during runtime!:
https://sweetcode.io/understanding-docker-image-layers/
The idea is that you can essentially change PARTS of an image, without rebuilding it entirely, which saves space and bandwidth.