{
  config,
  pkgs,
  lib,
  modulesPath,
  ...
}:
{

  imports = [
    "${modulesPath}/image/repart.nix"
  ];

  fileSystems = {
    # "/" = {
    #   fsType = "tmpfs";
    #   options = [
    #     "size=20%"
    #   ];
    # };
    "/" =
      let
        partConf = config.image.repart.partitions."root".repartConfig;
      in
      {
        device = "/dev/disk/by-partuuid/${partConf.UUID}";
        fsType = partConf.Format;
      };

    # "/var" =
    #   let
    #     partConf = config.image.repart.partitions."var".repartConfig;
    #   in
    #   {
    #     device = "/dev/disk/by-partuuid/${partConf.UUID}";
    #     fsType = partConf.Format;
    #   };

    "/boot" =
      let
        partConf = config.image.repart.partitions."esp".repartConfig;
      in
      {
        device = "/dev/disk/by-partuuid/${partConf.UUID}";
        fsType = partConf.Format;
      };

    # "/nix/store" =
    #   let
    #     partConf = config.image.repart.partitions."store".repartConfig;
    #   in
    #   {
    #     device = "/dev/disk/by-partlabel/${partConf.Label}";
    #     fsType = partConf.Format;
    #   };
  };

  boot.uki.name = "monkey";
  # fileSystems."/".device = "/dev/disk/by-label/nixos";
  # https://nixos.org/manual/nixos/stable/#sec-image-repart
  # https://x86.lol/generic/2024/08/28/systemd-sysupdate.html
  image.repart =
    let
      efiArch = pkgs.stdenv.hostPlatform.efiArch;
    in
    {
      name = config.boot.uki.name;
      # name = "image";
      # split = true;
      partitions = {
        "esp" = {
          # The contents to end up in the filesystem image.
          contents = {
            # "/EFI/BOOT/BOOTX64.EFI".source = "${pkgs.systemd}/lib/systemd/boot/efi/systemd-bootx64.efi";
            "/EFI/BOOT/BOOT${lib.toUpper efiArch}.EFI".source =
              "${pkgs.systemd}/lib/systemd/boot/efi/systemd-boot${efiArch}.efi";

            "/EFI/Linux/${config.system.boot.loader.ukiFile}".source =
              "${config.system.build.uki}/${config.system.boot.loader.ukiFile}";

            # https://man.archlinux.org/man/loader.conf.5
            "/loader/entries/loader.conf".source = pkgs.writeText "loader.conf" ''
              timeout 0
              editor yes
              default *
              logLevel=debug
            '';
            # "/loader/loader.conf".source = pkgs.writeText "loader.conf" ''
            #   timeout 0
            #   editor yes
            #   default *
            #   logLevel=debug
            # '';
            # nixos-*.conf
            # "/loader/entries/nixos.conf".source = pkgs.writeText "nixos.conf" ''
            #   title NixOS
            #   linux /EFI/nixos/kernel.efi
            #   initrd /EFI/nixos/initrd.efi
            #   options init=/nix/store/.../init root=LABEL=nixos
            # '';

            # systemd-boot configuration
            "/loader/loader.conf".source = (
              pkgs.writeText "$out" ''
                timeout 3
              ''
            );
          };
          # https://www.man7.org/linux//man-pages/man5/repart.d.5.html
          repartConfig = {
            Priority = 1;
            Type = "esp";
            MountPoint = "/boot";
            Format = "vfat";
            UUID = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa";
            SizeMinBytes = "500M";
            SizeMaxBytes = "500M";
          };
          # repartConfig = {
          #   Type = "esp";
          #   UUID = "c12a7328-f81f-11d2-ba4b-00a0c93ec93b"; # Well known
          #   Format = "vfat";
          #   SizeMinBytes = "256M";
          #   SplitName = "-";
          # };
        };
        "root" = {
          storePaths = [ config.system.build.toplevel ];
          repartConfig = {
            Priority = 2;
            Type = "root";
            Label = "nixos";
            MountPoint = "/";
            Format = "ext4";
            UUID = "bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb";
            # populates the fs twice
            Minimize = "guess";
            # Minimize = "off";
            # SizeMinBytes = "1G";
            # SizeMaxBytes = "20G";
          };

          # "store" = {
          #   storePaths = [ config.system.build.toplevel ];
          #   stripNixStorePrefix = true;
          #   repartConfig = {
          #     Type = "linux-generic";
          #     Label = "store_${config.system.image.version}";
          #     Format = "squashfs";
          #     Minimize = "off";
          #     ReadOnly = "yes";

          #     SizeMinBytes = "1G";
          #     SizeMaxBytes = "1G";
          #     SplitName = "store";
          #   };
          # };

          # # Placeholder for the second installed Nix store.
          # "store-empty" = {
          #   repartConfig = {
          #     Type = "linux-generic";
          #     Label = "_empty";
          #     Minimize = "off";
          #     SizeMinBytes = "1G";
          #     SizeMaxBytes = "1G";
          #     SplitName = "-";
          #   };
          # };

          # # Persistent storage
          # "var" = {
          #   repartConfig = {
          #     Type = "var";
          #     UUID = "4d21b016-b534-45c2-a9fb-5c16e091fd2d"; # Well known
          #     Format = "xfs";
          #     Label = "nixos-persistent";
          #     Minimize = "off";

          #     # Has to be large enough to hold update files.
          #     SizeMinBytes = "2G";
          #     SizeMaxBytes = "2G";
          #     SplitName = "-";

          #     # Wiping this gives us a clean state.
          #     FactoryReset = "yes";
          #   };
          # };
        };
      };
    };

  # disko.devices.disk.main = {
  #   device = "/dev/sda";
  #   type = "disk";
  #   content = {
  #     type = "gpt";
  #     partitions = {
  #       MBR = {
  #         priority = 0;
  #         size = "1M";
  #         type = "EF02";
  #       };
  #       ESP = {
  #         priority = 1;
  #         size = "500M";
  #         type = "EF00";
  #         content = {
  #           type = "filesystem";
  #           format = "vfat";
  #           mountpoint = "/boot";
  #         };
  #       };
  #       root = {
  #         priority = 2;
  #         size = "100%";
  #         content = {
  #           type = "filesystem";
  #           format = "ext4";
  #           mountpoint = "/";
  #         };
  #       };
  #     };
  #   };
  # };

}