system: add central lts kernel option

hosts/nullbox/configuration.nix

@@ -89,8 +89,7 @@
       };
     };
 
-    # temporary while i am away from server
-    boot.kernelPackages = pkgs.linuxPackages_6_6;
+    boot.kernelPackages = config.nixfiles.ltsKernel;
 
     networking.wg-quick.interfaces.wg0 = {
       configFile = "/etc/wireguard/wg0.conf";

hosts/rpi4/configuration.nix

@@ -33,8 +33,7 @@
     configurationLimit = 5;
   };
 
-  # temporary while i am away from server
-  boot.kernelPackages = pkgs.linuxPackages_6_6;
+  boot.kernelPackages = config.nixfiles.ltsKernel;
 
   nixfiles = {
     profile.server.enable = true;

system/default.nix

@@ -64,5 +64,12 @@ in
       type = flakeType;
       example = "home-manager";
     };
+
+    ltsKernel = lib.mkOption {
+      description = "Currently tested LTS kernelPackages, manually update after testing.";
+      default = pkgs.linuxPackages_6_6;
+      type = options.boot.kernelPackages.type;
+      readOnly = true;
+    };
   };
 }