{
  pkgs,
  hostSystem,
  releaseName,
  buildNumber ? "1",
  appDir,
}: let

  cpuArch = (pkgs.lib.systems.parse.mkSystemFromString hostSystem).cpu.name;

  pkgbuild = pkgs.writeText "isle-arch-PKGBUILD-${releaseName}-${cpuArch}" ''
    pkgname=isle
    pkgver=${builtins.replaceStrings ["-"] ["_"] releaseName}
    pkgrel=${buildNumber}
    pkgdesc="The foundation for an autonomous community cloud infrastructure"
    arch=('${cpuArch}')
    url="https://code.betamike.com/micropelago/isle"
    license=('AGPL-3.0-or-later')

    source=('src.tar.zst')
    md5sums=('SKIP')

    package() {
      cp -r etc "$pkgdir"/etc
      cp -r usr "$pkgdir"/usr
    }
  '';

  linuxRoot = (import ../default.nix).buildRoot {
    inherit pkgs appDir;
  };

in
  pkgs.stdenv.mkDerivation {
    name = "isle-arch-pkg-${releaseName}-${cpuArch}";

    nativeBuildInputs = [
      pkgs.zstd
      pkgs.pacman
      pkgs.fakeroot
      pkgs.libarchive
    ];

    inherit pkgbuild;
    src = linuxRoot;
    dontUnpack = true;

    buildPhase = ''
      tar -cf src.tar.zst --zstd --mode=a+rX,u+w -C "$src" .
      cp $pkgbuild PKGBUILD

      PKGEXT=".pkg.tar.zst" CARCH="${cpuArch}" makepkg \
        --nodeps \
        --config ${pkgs.pacman}/etc/makepkg.conf
    '';

    installPhase = ''
      mkdir -p $out
      cp *.pkg.tar.zst $out/
    '';

    # NOTE if https://github.com/NixOS/nixpkgs/issues/241911 is ever addressed
    # it'd be nice to add an automatic check using namcap here.
  }