diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..87a3018
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+result
+*.qcow2
diff --git a/flake.nix b/flake.nix
index be6f6fb..2bbe76d 100644
--- a/flake.nix
+++ b/flake.nix
@@ -8,42 +8,47 @@
     };
   };
 
-  outputs = inputs @ {
-    self,
-    nixpkgs,
-    nixpkgs-unstable,
-    home-manager,
-    ...
-  }: let
-    mkHost = hostname: graphical: {
-      imports = [
-        ./hosts/${hostname}/configuration.nix
-        ./modules/common
-        (import "${home-manager}/nixos")
-        (
-          if graphical
-          then ./modules/graphical
-          else null
-        )
-      ];
+  outputs =
+    inputs @ { self
+    , nixpkgs
+    , nixpkgs-unstable
+    , home-manager
+    , ...
+    }:
+    let
+      system = "x86_64-linux";
+      mkHost = hostname: {
+        imports = [
+          ./hosts/${hostname}/configuration.nix
+          ./modules/common
+          (import "${home-manager}/nixos")
+        ];
 
-      deployment = {
-        targetUser = "root";
-        targetHost = hostname;
-        allowLocalDeployment = true;
-      };
-    };
-  in {
-    formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.alejandra;
-    colmena = {
-      meta = {
-        nixpkgs = import nixpkgs {
-          system = "x86_64-linux";
-          overlays = [];
+        deployment = {
+          targetUser = "root";
+          targetHost = hostname;
+          allowLocalDeployment = true;
         };
       };
+    in
+    {
+      formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.alejandra;
+      colmena = {
+        meta = {
+          nixpkgs = import nixpkgs {
+            system = "x86_64-linux";
+            overlays = [ ];
+          };
+        };
 
-      bengal = mkHost "bengal" true;
+        bengal = mkHost "bengal";
+      };
+      nixosConfigurations.test = nixpkgs.lib.nixosSystem {
+        inherit system;
+        modules = [
+          ./hosts/test-vm/configuration.nix
+          (import "${home-manager}/nixos")
+        ];
+      };
     };
-  };
 }
diff --git a/hosts/bengal/configuration.nix b/hosts/bengal/configuration.nix
index 16317f2..b52b20a 100644
--- a/hosts/bengal/configuration.nix
+++ b/hosts/bengal/configuration.nix
@@ -12,6 +12,8 @@
     ./hardware-configuration.nix
   ];
 
+  cherrykitten.graphical.enable = true;
+
   boot.loader.systemd-boot.enable = true;
 
   networking.hostName = "bengal";
diff --git a/hosts/test-vm/configuration.nix b/hosts/test-vm/configuration.nix
new file mode 100644
index 0000000..5bbc5f8
--- /dev/null
+++ b/hosts/test-vm/configuration.nix
@@ -0,0 +1,39 @@
+{ config, lib, pkgs, ... }: {
+
+  imports = [
+    ../../modules/common
+    ../../modules/graphical
+  ];
+
+  cherrykitten.graphical.enable = false;
+
+  users.users.admin = {
+    isNormalUser = true;
+    extraGroups = [ "wheel" ];
+    password = "admin";
+    group = "admin";
+  };
+
+  users.groups.admin = { };
+
+  virtualisation.vmVariant = {
+    # following configuration is added only when building VM with build-vm
+    virtualisation = {
+      memorySize = 8192;
+      cores = 6;
+      graphics = true;
+    };
+  };
+
+  services.openssh = {
+    enable = true;
+    settings.PasswordAuthentication = lib.mkForce true;
+  };
+
+  networking.firewall.allowedTCPPorts = [ 22 ];
+  environment.systemPackages = with pkgs; [
+    htop
+  ];
+
+  system.stateVersion = "23.10";
+}
diff --git a/modules/common/default.nix b/modules/common/default.nix
index 19b7fed..13156f2 100644
--- a/modules/common/default.nix
+++ b/modules/common/default.nix
@@ -1,49 +1,63 @@
+{ lib
+, config
+, pkgs
+, ...
+}:
+let
+  cfg = config.cherrykitten.common;
+in
 {
-  lib,
-  config,
-  pkgs,
-  ...
-}: {
   imports = [
     ../users
     ./security.nix
     ./yubikey.nix
+    ../graphical
   ];
 
-  nix.settings.experimental-features = ["nix-command" "flakes"];
-
-  time.timeZone = "Europe/Berlin";
-
-  i18n.defaultLocale = "en_US.UTF-8";
-  console = {
-    font = "Lat2-Terminus16";
-    keyMap = lib.mkForce "de";
-    useXkbConfig = true; # use xkb.options in tty.
-  };
-
-  fonts = {
-    enableDefaultFonts = true;
-    packages = with pkgs; [
-      noto-fonts
-      noto-fonts-cjk
-      noto-fonts-emoji
-      monaspace
-      nerdfonts
-    ];
-    fontconfig = {
-      defaultFonts.emoji = ["Noto Emoji"];
-      defaultFonts.serif = ["Monaspace Xenon" "FiraCode Nerd Font" "Hack Nerd Font" "NotoSans Nerd Font"];
-      defaultFonts.sansSerif = ["Monaspace Xenon" "FiraCode Nerd Font" "Hack Nerd Font" "NotoSerif Nerd Font"];
-      defaultFonts.monospace = ["Monaspace Xenon" "FiraCode Nerd Font" "Hack Nerd Font"];
+  options.cherrykitten.common = {
+    test = lib.mkOption {
+      type = lib.types.str;
+      default = "nya";
+      example = "nyanya";
     };
   };
 
-  # Packages used on all systems
-  environment.systemPackages = with pkgs; [
-    git
-    openssl
-    rsync
-    pinentry
-    wget
-  ];
+  config = {
+    nix.settings.experimental-features = [ "nix-command" "flakes" ];
+
+    time.timeZone = "Europe/Berlin";
+
+    i18n.defaultLocale = "en_US.UTF-8";
+    console = {
+      font = "Lat2-Terminus16";
+      keyMap = lib.mkForce "de";
+      useXkbConfig = true; # use xkb.options in tty.
+    };
+
+    fonts = {
+      enableDefaultPackages = true;
+      packages = with pkgs; [
+        noto-fonts
+        noto-fonts-cjk
+        noto-fonts-emoji
+        monaspace
+        nerdfonts
+      ];
+      fontconfig = {
+        defaultFonts.emoji = [ "Noto Emoji" ];
+        defaultFonts.serif = [ "Monaspace Xenon" "FiraCode Nerd Font" "Hack Nerd Font" "NotoSans Nerd Font" ];
+        defaultFonts.sansSerif = [ "Monaspace Xenon" "FiraCode Nerd Font" "Hack Nerd Font" "NotoSerif Nerd Font" ];
+        defaultFonts.monospace = [ "Monaspace Xenon" "FiraCode Nerd Font" "Hack Nerd Font" ];
+      };
+    };
+
+    # Packages used on all systems
+    environment.systemPackages = with pkgs; [
+      git
+      openssl
+      rsync
+      pinentry
+      wget
+    ];
+  };
 }
diff --git a/modules/graphical/default.nix b/modules/graphical/default.nix
index 24e7f56..fba13a1 100644
--- a/modules/graphical/default.nix
+++ b/modules/graphical/default.nix
@@ -1,54 +1,63 @@
+{ pkgs
+, config
+, lib
+, ...
+}:
+let
+  cfg = config.cherrykitten.graphical;
+in
 {
-  pkgs,
-  config,
-  lib,
-  ...
-}: {
-  services.xserver = {
-    enable = true;
-    displayManager.sddm.enable = true;
-    desktopManager.plasma5.enable = true;
-    desktopManager.plasma5.bigscreen.enable = true;
-    libinput.enable = true;
-
-    xkb.layout = "de";
-    xkb.options = "caps:escape";
+  options.cherrykitten.graphical = {
+    enable = lib.mkEnableOption (lib.mdDoc "graphical stuffs");
   };
 
-  home-manager.users.sammy = {
-    programs = {
-      librewolf.enable = true;
+  config = lib.mkIf cfg.enable {
+    services.xserver = {
+      enable = true;
+      displayManager.sddm.enable = true;
+      desktopManager.plasma5.enable = true;
+      desktopManager.plasma5.bigscreen.enable = true;
+      libinput.enable = true;
 
-      kitty = {
-        enable = true;
-        theme = "Catppuccin-Mocha";
-        font = {
-          name = "Monaspace Xenon";
-          size = 12;
-        };
-        settings = {
-          # Seti-UI + Custom
-          "symbol_map U+E5FA-U+E62B" = "Symbols Nerd Font";
-          # Devicons
-          "symbol_map U+E700-U+E7C5" = "Symbols Nerd Font";
-          # Font Awesome
-          "symbol_map U+F000-U+F2E0" = "Symbols Nerd Font";
-          # Font Awesome Extension
-          "symbol_map U+E200-U+E2A9" = "Symbols Nerd Font";
-          # Material Design Icons
-          "symbol_map U+F500-U+FD46" = "Symbols Nerd Font";
-          # Weather
-          "symbol_map U+E300-U+E3EB" = "Symbols Nerd Font";
-          # Octicons
-          "symbol_map U+F400-U+F4A8,U+2665,U+26A1,U+F27C" = "Symbols Nerd Font";
-          # Powerline Extra Symbols
-          "symbol_map U+E0A3,U+E0B4-U+E0C8,U+E0CC-U+E0D2,U+E0D4" = "Symbols Nerd Font";
-          # IEC Power Symbols
-          "symbol_map U+23FB-U+23FE,U+2b58" = "Symbols Nerd Font";
-          # Font Logos
-          "symbol_map U+F300-U+F313" = "Symbols Nerd Font";
-          # Pomicons
-          "symbol_map U+E000-U+E00D" = "Symbols Nerd Font";
+      xkb.layout = "de";
+      xkb.options = "caps:escape";
+    };
+
+    home-manager.users.sammy = {
+      programs = {
+        librewolf.enable = true;
+
+        kitty = {
+          enable = true;
+          theme = "Catppuccin-Mocha";
+          font = {
+            name = "Monaspace Xenon";
+            size = 12;
+          };
+          settings = {
+            # Seti-UI + Custom
+            "symbol_map U+E5FA-U+E62B" = "Symbols Nerd Font";
+            # Devicons
+            "symbol_map U+E700-U+E7C5" = "Symbols Nerd Font";
+            # Font Awesome
+            "symbol_map U+F000-U+F2E0" = "Symbols Nerd Font";
+            # Font Awesome Extension
+            "symbol_map U+E200-U+E2A9" = "Symbols Nerd Font";
+            # Material Design Icons
+            "symbol_map U+F500-U+FD46" = "Symbols Nerd Font";
+            # Weather
+            "symbol_map U+E300-U+E3EB" = "Symbols Nerd Font";
+            # Octicons
+            "symbol_map U+F400-U+F4A8,U+2665,U+26A1,U+F27C" = "Symbols Nerd Font";
+            # Powerline Extra Symbols
+            "symbol_map U+E0A3,U+E0B4-U+E0C8,U+E0CC-U+E0D2,U+E0D4" = "Symbols Nerd Font";
+            # IEC Power Symbols
+            "symbol_map U+23FB-U+23FE,U+2b58" = "Symbols Nerd Font";
+            # Font Logos
+            "symbol_map U+F300-U+F313" = "Symbols Nerd Font";
+            # Pomicons
+            "symbol_map U+E000-U+E00D" = "Symbols Nerd Font";
+          };
         };
       };
     };
diff --git a/modules/users/default.nix b/modules/users/default.nix
index 5b4baa4..6346875 100644
--- a/modules/users/default.nix
+++ b/modules/users/default.nix
@@ -12,7 +12,7 @@
     };
   };
 
-  home-manager.useGlobalPkgs = true;
+  home-manager.useUserPackages = true;
   home-manager.users = {
     sammy.imports = [./sammy.nix];
   };