diff --git a/configuration/common.nix b/configuration/common.nix
new file mode 100644
index 0000000..8c2a11b
--- /dev/null
+++ b/configuration/common.nix
@@ -0,0 +1,112 @@
+{ pkgs, ... }:
+{
+  # NixOS version.
+  system.stateVersion = "25.05";
+
+  # Enable flakes.
+  nix.settings.experimental-features = [
+    "nix-command"
+    "flakes"
+  ];
+
+  # Allow unfree packages.
+  nixpkgs.config.allowUnfree = true;
+  
+  # Set time zone.
+  time.timeZone = "Australia/Perth";
+
+  # Select internationalisation properties.
+  i18n.defaultLocale = "en_AU.UTF-8";
+
+  i18n.extraLocaleSettings = {
+    LC_ADDRESS = "en_AU.UTF-8";
+    LC_IDENTIFICATION = "en_AU.UTF-8";
+    LC_MEASUREMENT = "en_AU.UTF-8";
+    LC_MONETARY = "en_AU.UTF-8";
+    LC_NAME = "en_AU.UTF-8";
+    LC_NUMERIC = "en_AU.UTF-8";
+    LC_PAPER = "en_AU.UTF-8";
+    LC_TELEPHONE = "en_AU.UTF-8";
+    LC_TIME = "en_AU.UTF-8";
+  };
+
+  # Configure keymap in X11.
+  services.xserver.xkb = {
+    layout = "us";
+    variant = "";
+  };
+
+  # Use fish shell
+  programs.fish = {
+    enable = true;
+    interactiveShellInit = ''
+      function n --wraps nnn --description 'support nnn quit and change directory'
+          if test -n "$NNNLVL" -a "$NNNLVL" -ge 1
+              echo "nnn is already running"
+              return
+          end
+
+          if test -n "$XDG_CONFIG_HOME"
+              set -x NNN_TMPFILE "$XDG_CONFIG_HOME/nnn/.lastd"
+          else
+              set -x NNN_TMPFILE "$HOME/.config/nnn/.lastd"
+          end
+
+          command ${pkgs.nnn}/bin/nnn $argv
+
+          if test -e $NNN_TMPFILE
+              source $NNN_TMPFILE
+              rm -- $NNN_TMPFILE
+          end
+      end
+    '';
+  };
+
+  programs.bash = {
+    interactiveShellInit = ''
+      if [[ $(${pkgs.procps}/bin/ps --no-header --pid=$PPID --format=comm) != "fish" && -z ''${BASH_EXECUTION_STRING} ]]
+      then
+        shopt -q login_shell && LOGIN_OPTION='--login' || LOGIN_OPTION=""
+        exec ${pkgs.fish}/bin/fish $LOGIN_OPTION
+      fi
+    '';
+  }; # https://nixos.wiki/wiki/Fish#Setting_fish_as_your_shell
+
+  # Install some packages.
+  programs.git.enable = true;
+
+  programs.neovim = {
+    enable = true;
+    defaultEditor = true; # Use neovim as default terminal editor.
+    configure = {
+      customRC = ''
+        set expandtab
+        set shiftwidth=2
+        set tabstop=8
+        set softtabstop=2
+        set number
+        colorscheme kanagawa-dragon
+      '';
+      packages.myVimPackage = with pkgs.vimPlugins; {
+        start = [ kanagawa-nvim ];
+      };
+    };
+  };
+
+  environment.systemPackages = with pkgs; [
+    aria2
+    btop
+    lynx
+    ncdu
+    nnn
+    rsync
+    tmux
+    trash-cli
+  ];
+
+  # Enable avahi hostname resolution.
+  services.avahi = {
+    enable = true;
+    nssmdns4 = true;
+  };
+}
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