Nix docker layering

Allows to customize the layering logic as you need it. Especially useful for large containers.

Other projects

Official Docs: https://nix.dev/tutorials/nixos/building-and-running-docker-images.html
Default Way: https://grahamc.com/blog/nix-and-layered-docker-images/
Faster Way: https://blog.eigenvalue.net/2023-nix2container-everything-once/

But what if you want to implement/experiment with custom strategies? This project might help!

Example usage

{ pkgs ? import <nixpkgs> {} }:
let
  docker_layering = import (pkgs.fetchTarball {
    url = "https://github.com/matthid/nix-docker-layering/archive/1.0.0.tar.gz";
    sha256 = "0g5y363m479b0pcyv0vkma5ji3x5w2hhw0n61g2wgqaxzraaddva";
  }) { inherit pkgs; };
in
docker_layering.streamLayeredImage {
  # Select your strategy or implement your own!
  slurpfileGenerator = docker_layering.generators.equal;
  maxLayers = 20;
  name = "docker_layering_test";
  tag = "latest";

  contents = [
    pkgs.coreutils
    pkgs.findutils
    pkgs.gnugrep
    pkgs.gnused
    pkgs.gawk
    pkgs.bashInteractive
    pkgs.which
    pkgs.file
    pkgs.binutils
    pkgs.diffutils
    pkgs.less
    pkgs.gzip
    pkgs.btar
    pkgs.nano
  ];
  config = {
    Entrypoint = ["${pkgs.bashInteractive}/bin/bash"];
  };
}

Existing stratgies

generators.default -> Similar to the "Default Way" as explained in the blogpost above.
generators.equal -> Instead of single package layers, group them by equal size.

Create your own strategy

Look at the existing generators, define your own accordingly. They don't need to be written in python basically a generator is a derivation which has a json input file as parameter (all the context you will need) and should write a json output file (a docker slurpfile for the layers)

Contributing

Change and run $(nix-build test/usage.nix) | docker load to test.