nixos-servers/nixos/modules/data-disk.nix

{ lib, config, ... }:
let cfg = config.custom.dataDisk;
in {
  options = {
    custom = {
      dataDisk = {
        enable = lib.mkOption {
          default = false;
          type = lib.types.bool;
          description = ''
            Whether to automatically mount a disk to be used as a data disk.
          '';
        };

        mountPoint = lib.mkOption {
          default = "/mnt/data";
          type = lib.types.str;
          description = ''
            Mount point of the data disk (if enabled).
          '';
        };

        devicePath = lib.mkOption {
          default = "/dev/sda1";
          type = lib.types.str;
          description = ''
            Path of the device to be used as a data disk.
          '';
        };
      };
    };
  };

  config = lib.mkIf cfg.enable {
    fileSystems.${cfg.mountPoint} = { device = cfg.devicePath; };
  };
}