Proof-of-concept Docker image building of multiple packages, with Nix

buildContainer.nix

{ pkgs ? import <nixpkgs> {}, name, packages ? {}}:

with pkgs;
let
  # We need bash and coreutils to display the container "run" message;
  # dockerTools.buildImage expects a list of derivations, not a set
  required = { inherit bash coreutils; };
  contents = builtins.attrValues (required // packages);

  prettyPrint = import ./prettyPrint.nix {};

in dockerTools.buildImage {
  inherit name contents;

  config = {
    Cmd = [ "${bash}/bin/bash" "-c" ''
      ( ${coreutils}/bin/cat | ${coreutils}/bin/fmt -s ) >&2 <<EOF
      This is the "${name}" container, containing the following software:

      ${prettyPrint packages}

      Execute these tools explicitly from within the container, rather than running the container itself.
      EOF
    '' ];
  };
}

default.nix

let
  pkgs = import <nixpkgs> {};
  buildContainer = import ./buildContainer.nix;

in buildContainer {
  name = "bionix-poc";
  packages = with pkgs; { inherit samtools bwa; };
}

prettyPrint.nix

# Pretty printer for package/derivation sets
{ bullet ? "*", recSep ? "\n", emptyText ? "<No packages installed>" }:
packageSet:

with builtins;
let
  # Pretty printer for derivations
  ppDrv = drv:
    let parsed = parseDrvName drv.name;
    in "${bullet} ${parsed.name} v${parsed.version}";

  # Extract derivations from set
  packages = attrValues packageSet;
  isEmpty = length packages == 0;

in if isEmpty
  then emptyText
  else concatStringsSep recSep (map ppDrv packages)

Rather than using ociTools, we can create Singularity images with:

singularity build my-image.sif docker-archive:$(nix-build)