nix-openwrt-imagebuilder

Generate OpenWRT images from Nix derivations using the official ImageBuilders that are provided upstream.

For OpenWRT releases since 19.07 there is profile helper functionality that helps you find the proper image specification (target, variant) according to your hardware's profile name.

Background

In an ideal world, OpenWRT would be built from source in many fine-grained Nix derivations. Until someone implements that (please do!), this project exists to reuse the binary ImageBuilders that are included in every OpenWRT release. They are only available for x86_64-linux hosts.

The ImageBuilder can generate new sysupgrade images with a customized set of packages and included files.

Usage with vanilla Nix

let
  pkgs = import <nixpkgs> {};

  # use fetchurl, Hydra inputs, or something else to refer to this project
  openwrt-imagebuilder = ../nix-openwrt-imagebuilder;

  profiles = import (openwrt-imagebuilder + "/profiles.nix") { inherit pkgs; };

  # example: find target/variant for an old Fritzbox
  config = profiles.identifyProfile "avm_fritz7412" // {
    # add package to include in the image, ie. packages that you don't
    # want to install manually later
    packages = [ "tcpdump" ];

    disabledServices = [ "dnsmasq" ];

    # include files in the images.
    # to set UCI configuration, create a uci-defauts scripts as per
    # official OpenWRT ImageBuilder recommendation.
    files = pkgs.runCommand "image-files" {} ''
      mkdir -p $out/etc/uci-defaults
      cat > $out/etc/uci-defaults/99-custom <<EOF
      uci -q batch << EOI
      set system.@system[0].hostname='testap'
      commit
      EOI
      EOF
    '';
  };

in
  # actually build the image
  import (openwrt-imagebuilder + "/builder.nix") config

Usage with Nix Flakes

{
  inputs = {
    openwrt-imagebuilder.url = "github:astro/nix-openwrt-imagebuilder";
  };
  outputs = { self, nixpkgs, openwrt-imagebuilder }: {
    packages.x86_64-linux.my-router =
      let
        pkgs = nixpkgs.legacyPackages.x86_64-linux;

        profiles = openwrt-imagebuilder.lib.profiles { inherit pkgs; };

        config = profiles.identifyProfile "avm_fritz7412" // {
          # add package to include in the image, ie. packages that you don't
          # want to install manually later
          packages = [ "tcpdump" ];

          disabledServices = [ "dnsmasq" ];

          # include files in the images.
          # to set UCI configuration, create a uci-defauts scripts as per
          # official OpenWRT ImageBuilder recommendation.
          files = pkgs.runCommand "image-files" {} ''
            mkdir -p $out/etc/uci-defaults
            cat > $out/etc/uci-defaults/99-custom <<EOF
            uci -q batch << EOI
            set system.@system[0].hostname='testap'
            commit
            EOI
            EOF
          '';
        };

      in
        openwrt-imagebuilder.lib.build config;
  };
}

Refreshing hashes

downloads.openwrt.org appears to be never at rest. That's why we update the hashes subdirectory daily with a Github action.

If you still encounter hash mismatch in fixed-output derivation in between these updates, update them yourself:

nix run .#generate-hashes $(sed -e 's/"//g' latest-release.nix)

If your flake.nix has this project in its inputs, then you can build with your local working copy using nix build --override-input openwrt-imagebuilder git+file:///... .#...