multi-boot-helper.nix

with import <nixpkgs> {};
let
  netboot = import (pkgs.path + "/nixos/lib/eval-config.nix") {
      modules = [
        (pkgs.path + "/nixos/modules/installer/netboot/netboot-minimal.nix")
        module
      ];
    };
  module = {
    # you will want to add options here to support your filesystem
    # and also maybe ssh to let you in
    boot.supportedFilesystems = [ "zfs" ];
  };
  grubFragment = writeText "grub.cfg" (builtins.unsafeDiscardStringContext ''
    menuentry "Nixos Installer" {
      linux ($drive1)/nixos-kernel init=${netboot.config.system.build.toplevel}/init ${toString netboot.config.boot.kernelParams}
      initrd ($drive1)/nixos-initrd
    }
  '');
in runCommand "multi-boot-helper" {} ''
  mkdir $out
  cp -L ${netboot.config.system.build.kernel}/bzImage $out/nixos-kernel
  cp -L ${netboot.config.system.build.netbootRamdisk}/initrd $out/nixos-initrd
  cp ${grubFragment} $out/grub-fragment.cfg
''