added options to build with to avoid removing and re-adding stuff

devices/desktop/default.nix

@@ -1,6 +1,7 @@
 { config, pkgs, ... }: {
   imports = [
     ./hardware-config.nix
+    ./options.nix
   ];
 
   networking.hostName = "desktop";

devices/desktop/options.nix

@@ -0,0 +1,5 @@
+{ ... }: {
+  withNiri = false;
+  withGnome = true;
+  withVM = false;
+}

devices/surface/default.nix

@@ -1,6 +1,7 @@
 { pkgs, ... }: {
   imports = [
     ./hardware-config.nix
+    ./options.nix
   ];
 
   networking.hostName = "surface";

devices/surface/options.nix

@@ -0,0 +1,5 @@
+{ ... }: {
+  withNiri = false;
+  withGnome = true;
+  withVM = false;
+}

modules/system/default.nix

@@ -2,80 +2,88 @@
 # your system.  Help is available in the configuration.nix(5) man page
 # and in the NixOS manual (accessible by running ‘nixos-help’).
 
-{ pkgs, ... }: {
+{ pkgs, lib, config, ... }: {
+  options = {
+    withNiri = with lib; mkEnableOption "Enable niri";
+    withGnome = with lib; mkEnableOption "Enable gnome";
+    withVM = with lib; mkEnableOption "Enable VM related configuration";
+  };
+
   imports = [
     ./audio.nix
     ./containers.nix
     ./fonts.nix
     ./gnome
     ./niri
+    ./virt.nix
   ];
 
-
-  # Allow packages from nixpkgs
-  nixpkgs.config = {
-    allowUnfree = true;
-  };
-
-  #Optimise nix store
-  nix = {
-    gc = {
-      automatic = true;
-      dates = "weekly";
-      options = "--delete-older-than 1w";
+  config = {
+    # Allow packages from nixpkgs
+    nixpkgs.config = {
+      allowUnfree = true;
     };
-    settings.auto-optimise-store = true;
-  };
 
-  # Enable nix flakes
-  nix.settings.experimental-features = [ "nix-command" "flakes" ];
+    #Optimise nix store
+    nix = {
+      gc = {
+        automatic = true;
+        dates = "weekly";
+        options = "--delete-older-than 1w";
+      };
+      settings.auto-optimise-store = true;
+    };
 
-  # Disable documentation
-  documentation.nixos.enable = false;
+    # Enable nix flakes
+    nix.settings.experimental-features = [ "nix-command" "flakes" ];
 
-  # Enable networking
-  networking.networkmanager.enable = true;
+    # Disable documentation
+    documentation.nixos.enable = false;
 
-  # Set your time zone.
-  time.timeZone = "Europe/Amsterdam";
+    # Enable networking
+    networking.networkmanager.enable = true;
 
-  # Select internationalisation properties.
-  i18n.defaultLocale = "en_US.UTF-8";
+    # Set your time zone.
+    time.timeZone = "Europe/Amsterdam";
 
-  i18n.extraLocaleSettings = {
-    LC_ADDRESS = "en_US.UTF-8";
-    LC_IDENTIFICATION = "en_US.UTF-8";
-    LC_MEASUREMENT = "en_US.UTF-8";
-    LC_MONETARY = "en_US.UTF-8";
-    LC_NAME = "en_US.UTF-8";
-    LC_NUMERIC = "en_US.UTF-8";
-    LC_PAPER = "en_US.UTF-8";
-    LC_TELEPHONE = "en_US.UTF-8";
-    LC_TIME = "en_US.UTF-8";
-  };
+    # Select internationalisation properties.
+    i18n.defaultLocale = "en_US.UTF-8";
 
-  # Enable the X11 windowing system.
-  services.xserver.enable = true;
+    i18n.extraLocaleSettings = {
+      LC_ADDRESS = "en_US.UTF-8";
+      LC_IDENTIFICATION = "en_US.UTF-8";
+      LC_MEASUREMENT = "en_US.UTF-8";
+      LC_MONETARY = "en_US.UTF-8";
+      LC_NAME = "en_US.UTF-8";
+      LC_NUMERIC = "en_US.UTF-8";
+      LC_PAPER = "en_US.UTF-8";
+      LC_TELEPHONE = "en_US.UTF-8";
+      LC_TIME = "en_US.UTF-8";
+    };
 
-  # Remove XTerm
-  services.xserver.excludePackages = [ pkgs.xterm ];
+    # Enable the X11 windowing system.
+    services.xserver.enable = true;
 
-  # Configure keymap in X11
-  services.xserver = {
-    layout = "us";
-    xkbVariant = "";
-  };
+    # Remove XTerm
+    services.xserver.excludePackages = [ pkgs.xterm ];
 
-  # Enable CUPS to print documents.
-  services.printing.enable = false;
+    # Configure keymap in X11
+    services.xserver = {
+      layout = "us";
+      xkbVariant = "";
+    };
 
-  # Security
-  security.rtkit.enable = true;
+    # Enable CUPS to print documents.
+    services.printing.enable = false;
 
-  # Define a user account. Don't forget to set a password with ‘passwd’.
-  users.users.twoneis = {
-    isNormalUser = true;
-    description = "twoneis";
-    extraGroups = [ "networkmanager" "wheel" ];
+    # Security
+    security.rtkit.enable = true;
+
+    # Define a user account. Don't forget to set a password with ‘passwd’.
+    users.users.twoneis = {
+      isNormalUser = true;
+      description = "twoneis";
+      extraGroups = [ "networkmanager" "wheel" ];
+    };
   };
 }

modules/system/gnome/default.nix

@@ -1,4 +1,4 @@
-{ pkgs, ... }: {
+{ pkgs, lib, config, ... }: lib.mkIf (config.withGnome) {
   # Enable the GNOME Desktop Environment.
   services.xserver.displayManager.gdm.enable = true;
   services.xserver.desktopManager.gnome.enable = true;

modules/system/niri/default.nix

@@ -1,3 +1,3 @@
-{ ... }: {
+{ lib, config, ... }: lib.mkIf (config.withNiri) {
   programs.niri.enable = true;
 }

modules/system/virt.nix

@@ -0,0 +1,5 @@
+{ lib, config, ... }: lib.mkIf (config.withVM) {
+  virtualisation.libvirtd.enable = true;
+  programs.virt-manager.enable = true;
+  users.users.twoneis.extraGroups = [ "libvirtd" ];
+}