{
  description = "PatOS is a minimal, immutable Linux distribution specialized for the Patagia Platform.";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  };

  outputs =
    {
      self,
      flake-utils,
      nixpkgs,
    }:
    flake-utils.lib.eachDefaultSystem (
      system:
      let
        pkgs = import nixpkgs { inherit system; };
      in
      {
        packages = {
          default = self.packages.${system}.image;
          image = pkgs.writeShellScriptBin "image" ''
            echo "make UKI..."
            ${self.packages.${system}.systemd.out}/bin/ukify build \
            --linux ${self.packages.${system}.kernel.kernel}/bzImage \
            --initrd ./out/initrd.gz \
            --cmdline "console=ttyS0" \
            -o patos.uki
          '';

          kernel = pkgs.callPackage ./kernel { };
          initrd = pkgs.writeShellScriptBin "mkinitrd" ''
            echo "make initrd..."
            mkdir -p out/lib
            # copy systemd
            cp -r ${self.packages.${system}.systemd.out}/* out/

            # get shared libs
            pushd out
            find . -type f -executable | xargs ldd | awk '{print $3}' | grep -v systemd | sort -u | xargs cp -t lib

            # gen initrd
            find . -print0 | ${pkgs.lib.getExe pkgs.cpio} --null --owner=root:root -o --format=newc | ${pkgs.lib.getExe pkgs.gzip} -9 > initrd.gz
          '';
          systemd = pkgs.callPackage ./systemd { };
        };

        checks = {
          simple-test = pkgs.runCommand "simple-test" { } ''
            ${self.packages.${system}.default}/bin/my-program
            touch $out
          '';
        };

        formatter = pkgs.nixpkgs-fmt;

        devShells.default = pkgs.mkShell {
          buildInputs = with pkgs; [
            erofs-utils
            just
            nixd
            nixfmt-rfc-style
            squashfs-tools-ng
          ];
        };

      }
    );
}