add zfs module with options

modules/nixos/hardware/default.nix

@@ -10,6 +10,7 @@
     ./server.nix
     ./sleep.nix
     ./wifi.nix
+    ./zfs.nix
   ];
 
   options = {

modules/nixos/hardware/zfs.nix

@@ -0,0 +1,14 @@
+{ config, pkgs, lib, ... }: {
+
+  options = { zfs.enable = lib.mkEnableOption "ZFS file system."; };
+
+  config =
+    lib.mkIf (pkgs.stdenv.isLinux && config.server && config.zfs.enable) {
+
+      # Only use compatible Linux kernel, since ZFS can be behind
+      boot.kernelPackages =
+        config.boot.zfs.package.latestCompatibleLinuxPackages;
+
+    };
+
+}