{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
    nixos-generators = {
      url = "github:nix-community/nixos-generators";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    xc = {
      url = "github:joerdav/xc";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { nixpkgs, nixos-generators, xc, ... }:
    let
      pkgsForSystem = system: import nixpkgs {
        inherit system;
        overlays = [
          (final: prev: { xc = xc.packages.${system}.xc; })
        ];
      };
      allVMs = [ "x86_64-linux" "aarch64-linux" ];
      forAllVMs = f: nixpkgs.lib.genAttrs allVMs (system: f {
        inherit system;
        pkgs = pkgsForSystem system;
      });
    in
    {
      packages = forAllVMs ({ system, pkgs }: {
        vm = nixos-generators.nixosGenerate {
          system = system;
          specialArgs = {
            pkgs = pkgs;
          };
          modules = [
            {
              # Pin nixpkgs to the flake input, so that the packages installed
              # come from the flake inputs.nixpkgs.url.
              nix.registry.nixpkgs.flake = nixpkgs;
              # set disk size to to 20G
              virtualisation.diskSize = 20 * 1024;
            }
            # Apply the rest of the config.
            ./configuration.nix
          ];
          format = "raw";
        };
      });
    };
}

{
  # Enable binfmt emulation of aarch64-linux.
  boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
}

# Define qemu-arm-static source.
let qemu-arm-static = pkgs.stdenv.mkDerivation {
  name = "qemu-arm-static";
  src = builtins.fetchurl {
    url = "https://github.com/multiarch/qemu-user-static/releases/download/v6.1.0-8/qemu-arm-static";
    sha256 = "06344d77d4f08b3e1b26ff440cb115179c63ca8047afb978602d7922a51231e3";
  };
  dontUnpack = true;
  installPhase = "install -D -m 0755 $src $out/bin/qemu-arm-static";
};
in {
  # Enable binfmt emulation of extra binary formats (armv7l-linux, for exmaple).
  boot.binfmt.registrations.arm = {
    interpreter = "${qemu-arm-static}/bin/qemu-arm-static";
    magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00'';
    mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\x00\xff\xfe\xff\xff\xff'';
  };

  # Define additional settings for nix.
  nix.extraOptions = ''
    extra-platforms = armv7l-linux
  '';
  nix.sandboxPaths = [ "/run/binfmt/arm=${qemu-arm-static}/bin/qemu-arm-static" ];
}

{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-unstable";
    nixos-generators = {
      url = "github:nix-community/nixos-generators";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };
  outputs = { self, nixpkgs, nixos-generators, ... }: {

    # A single nixos config outputting multiple formats.
    # Alternatively put this in a configuration.nix.
    nixosModules.myFormats = { config, ... }: {
      imports = [
        nixos-generators.nixosModules.all-formats
      ];

      nixpkgs.hostPlatform = "x86_64-linux";

      # customize an existing format
      formatConfigs.vmware = { config, ... }: {
        services.openssh.enable = true;
      };

      # define a new format
      formatConfigs.my-custom-format = { config, modulesPath, ... }: {
        imports = [ "${toString modulesPath}/installer/cd-dvd/installation-cd-base.nix" ];
        formatAttr = "isoImage";
        fileExtension = ".iso";
        networking.wireless.networks = {
          # ...
        };
      };
    };

    # a machine consuming the module
    nixosConfigurations.my-machine = nixpkgs.lib.nixosSystem {
      modules = [ self.nixosModules.myFormats ];
    };
  };
}

{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-unstable";
    nixos-generators = {
      url = "github:nix-community/nixos-generators";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };
  outputs = { self, nixpkgs, nixos-generators, ... }: {
    packages.x86_64-linux = {
      vmware = nixos-generators.nixosGenerate {
        system = "x86_64-linux";
        modules = [
          # you can include your own nixos configuration here, i.e.
          # ./configuration.nix
        ];
        format = "vmware";
        
        # optional arguments:
        # explicit nixpkgs and lib:
        # pkgs = nixpkgs.legacyPackages.x86_64-linux;
        # lib = nixpkgs.legacyPackages.x86_64-linux.lib;
        # additional arguments to pass to modules:
        # specialArgs = { myExtraArg = "foobar"; };
        
        # you can also define your own custom formats
        # customFormats = { "myFormat" = <myFormatModule>; ... };
        # format = "myFormat";
      };
      vbox = nixos-generators.nixosGenerate {
        system = "x86_64-linux";
        format = "virtualbox";
      };
    };
  };
}