nixery VS nix2container

The ones from https://nixery.dev/

You can build your own with https://nixery.dev/

I built a service for doing this ad-hoc via image names a few years ago and it enjoys some popularity with CI & debugging use-cases: https://nixery.dev/

name is eerily similar to `nixpkgs`, i.e. the monorepo that defines all packages and one of the underlying technologies here. i get the play on buildpacks, but still, as a nix user it makes me do a double take reading the name

this is neat though, and in political terms, the elevator pitch mentions nix itself as an implementation detail in passing. hopefully, if this catches on, it'll function as a non-threatening gateway drug to nix itself, when users inevitably go digging into the weeds

for anyone interested, prior art on the nix container front: https://nixery.dev

Wow, this is excellent! At a previous job, we had been using k8s + knative to spin up containers on demand, and likewise were unhappy with the delays. Spawner seems excellent.

One question: have you had to do any custom container builds on demand, and if so, have you had to deal with large containers (e.g. a Python base image with a few larger packages installed from PyPI)? We would run up against extremely long build image times using tools like kaniko, and caching would typically have only a limited benefit.

I was experimenting using Nix to maybe solve some of these problems, but never got far enough to run a speed test, and then left the job before finishing. But it seems to me some sort of algorithm like Nixery uses (https://nixery.dev) to generate cacheable layers with completely repeatable builds and nothing extraneous would help.

Maybe that's not a problem you had to solve, but if it is, I'd love your thoughts.

Nixery – Docker images on the fly with Nix\ (38 comments)

No discussion about Nix-built containers is complete with nix2container:

https://github.com/nlewo/nix2container

It is truly magical for handling large, multi-layered containers. Instead of building the container archives themselves and storing them in the nix store, it builds a JSON manifest that is consumed by a lightly patched version of skopeo that streams the layers directly to either your local container engine or the registry.

This means you never rebuild or reupload a container layer that is unchanged.

- Container images are built with https://github.com/nlewo/nix2container instead of Nix's built-in docker tools, because nix2container allows configuration of layers and thus makes it easier to share layers between images and improve layer caching.

As for integrating it into our CI pipeline, this is pretty much CI system agnostic as all you have to do is run `nix build ...` inside the pipeline, generating a `result` directory or file as an artifact that, in the case of nix2container, can be pushed to your container image registry.

dockerTools is the canonical way, but https://github.com/nlewo/nix2container seems to be gaining support as it's faster and doesn't use so much disk space while building.

> The key factor behind our decision was the realization that while Docker images are industry standard, moving around 100s of megabytes of images seems unnecessarily heavy-handed when we just need to synchronize a small change.

I think the culprit is more the GitHub Actions cache than Docker since it seems to be hard to get a clean cache management. I'm not sure about caching Docker image layers, but caching the Nix store with GitHub Actions is pretty complicated (not even sure it's possible): this means we have to download all required Nix store paths on each run, but i consider this is because of a GitHub Action cache limitation.

So, did you consider using another CI, which offers better caching mechanisms?

With a CI able to preserve the Nix store (Hydra[1] or Hercules[2] for instance), I think nix2container (author here) could also fit almost all of your requirements ("composability", reproducibility, isolation) and maybe provide better performances because it is able to split your application into several layers [2][3].

Note i'm pretty sure a lot of Docker CI also allows to efficiently build Docker images.

[1] https://hercules-ci.com/

[2] https://grahamc.com/blog/nix-and-layered-docker-images

[3] https://github.com/nlewo/nix2container/blob/85670cab354f7df6...

FYI, the nix2container [1] project (author here) aims to speedup the standard Nix container workflow (dockerTools.buildImage) by basically skipping the tarball step: it directly streams non already pushed layers.

[1] https://github.com/nlewo/nix2container

To get Rust incremental builds, did you consider using something such as crane https://github.com/ipetkov/crane ?

And regarding OCI images, i built nix2container (https://github.com/nlewo/nix2container) to speed up image build and push times.

For a more modern iteration of that idea, check out https://github.com/nlewo/nix2container

It has all the benefits of OP but produces the images much faster, and with less on-disk usage.

I've been using nix2container[1] for awhile now. It looks like this depends on Docker, have you guys considered removing that dependency? It shouldn't be necessary to create an OCI compliant image with Nix.

[1]: https://github.com/nlewo/nix2container

With https://github.com/nlewo/nix2container, I'm trying to make a more standalone tool. Basically, a Go binary takes a reference graph and produces a JSON file describing a container image. This JSON file is then ingested by a Skopeo fork (it adds a new `transport`) to produce images (to file, registries,...).

Currently, it supports the dockerTools layering algorithm and is designed to work with Guix [1] as well;)

[1] https://github.com/nlewo/nix2container/blob/065e5b108650ee4c...