flake: export nixosModules.gaming for guests with their own hardware

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

flake.nix

@@ -39,19 +39,44 @@
     } @ inputs:
     let
       system = "x86_64-linux";
-      mkHost = hostname: extraModules: nixpkgs.lib.nixosSystem {
-        inherit system;
-        specialArgs = { inherit inputs; };
-        modules = [
+      baseModules = hostname: [
         ./hosts/${hostname}.nix
         ./common.nix
         home-manager.nixosModules.home-manager
         stylix.nixosModules.stylix
         ./settings/stylix.nix
-        ] ++ extraModules;
+      ];
+      mkHost = hostname: extraModules: nixpkgs.lib.nixosSystem {
+        inherit system;
+        specialArgs = { inherit inputs; };
+        modules = baseModules hostname ++ extraModules;
       };
     in
     {
+      # Everything FredOS-Gaming is, minus the hardware — for anyone who wants
+      # to run this config on their own machine. They import this module next
+      # to their own hardware-configuration.nix from their own flake (readme.md
+      # has the snippet). `_module.args` stands in for mkHost's specialArgs,
+      # which a plain module can't set.
+      nixosModules.gaming = { lib, ... }: {
+        imports = baseModules "FredOS-Gaming";
+        _module.args.inputs = inputs;
+
+        # Hostname gates every FredOS-Gaming module, so it has to keep matching.
+        # These four otherwise live in hosts/hardware/FredOS-Gaming.nix, which
+        # is exactly the file a guest replaces.
+        networking.hostName = "FredOS-Gaming";
+        nixpkgs.hostPlatform = lib.mkDefault system;
+        system.stateVersion = lib.mkDefault "25.11";
+        boot.loader.systemd-boot.enable = lib.mkDefault true;
+        boot.loader.efi.canTouchEfiVariables = lib.mkDefault true;
+
+        # nordhammer.it is my build server and those are my SSH keys; neither
+        # belongs on someone else's machine.
+        nix.distributedBuilds = lib.mkForce false;
+        users.users.fred.openssh.authorizedKeys.keys = lib.mkForce [ ];
+      };
+
       nixosConfigurations = {
         FredOS-Gaming      = mkHost "FredOS-Gaming"      [ ./hosts/hardware/FredOS-Gaming.nix ];
         FredOS-Mediaserver = mkHost "FredOS-Mediaserver" [ ./hosts/hardware/FredOS-Mediaserver.nix ];

readme.md

@@ -139,6 +139,47 @@ After this succeeds, the plain `update` alias works from then on.
 
 ---
 
+## Running the desktop on someone else's machine
+
+`nixosModules.gaming` is the whole FredOS-Gaming desktop — Hyprland, quickshell,
+stylix theming, Steam, the lot — with `hosts/hardware/FredOS-Gaming.nix` left
+out. Import it from your own flake alongside your own
+`/etc/nixos/hardware-configuration.nix`, which stays on your machine and never
+touches this repo, so `nix flake update` keeps pulling my changes without ever
+overwriting your disks and GPU:
+
+```nix
+{
+  inputs.fredos.url = "git+https://forg.gregersen.it/rope/nixos";
+
+  outputs = { self, fredos, ... }: {
+    nixosConfigurations.mine = fredos.inputs.nixpkgs.lib.nixosSystem {
+      modules = [
+        fredos.nixosModules.gaming
+        ./hardware-configuration.nix
+      ];
+    };
+  };
+}
+```
+
+Then `sudo nixos-rebuild switch --flake .#mine`.
+
+Notes:
+
+- The hostname stays `FredOS-Gaming` — every module in here is gated on it, so
+  changing it switches the desktop off.
+- The module drops my build server and my SSH keys, and defaults
+  `system.stateVersion`, `nixpkgs.hostPlatform` and systemd-boot so a stock
+  `hardware-configuration.nix` is enough. All `mkDefault`, so override freely.
+- The CachyOS kernel and its binary cache live in the hardware file, so you
+  won't get them. Copy those lines out of `hosts/hardware/FredOS-Gaming.nix` if
+  you want them.
+- The user is `fred` with passwordless sudo. `passwd fred` after the first
+  switch.
+- My monitor layout (`DP-3`, 3440x1440@180) is in `hosts/FredOS-Gaming.nix`;
+  override `wayland.windowManager.hyprland.settings.monitor` for yours.
+
 ## Flake inputs
 
 | Input | Source |