diff --git a/modules/base/default.nix b/modules/base/default.nix
index ddb45b7..3047db1 100644
--- a/modules/base/default.nix
+++ b/modules/base/default.nix
@@ -3,6 +3,7 @@
     ../options
 
     #
+    ./nix.nix
 
     ../home
   ];
diff --git a/modules/base/nix.nix b/modules/base/nix.nix
new file mode 100644
index 0000000..2bf0877
--- /dev/null
+++ b/modules/base/nix.nix
@@ -0,0 +1,62 @@
+{
+  pkgs,
+  inputs,
+  ...
+}: {
+  nix = {
+    package = pkgs.lix;
+
+    # Pin system <nixpkgs> to flake nixpkgs version.
+    # i.e. for use in pkgs = import <nixpkgs> {}.
+    nixPath = ["nixpkgs=${inputs.nixpkgs}"];
+
+    # Pin flake registry nixpkgs to flake nixpkgs version.
+    # i.e. for use in nix search nixpkgs.
+    registry = {
+      nixpkgs.flake = inputs.nixpkgs;
+    };
+
+    settings = {
+      experimental-features = ["nix-command" "flakes"];
+
+      trusted-users = [
+        "root"
+        # @wheel/@admin are added in OS specific modules.
+      ];
+
+      # Set up caches.
+      extra-substituters = [
+        "https://marleyos.cachix.org"
+        "https://nix-community.cachix.org"
+      ];
+
+      trusted-public-keys = [
+        "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+        "marleyos.cachix.org-1:q2kEtqvS5CoQ8BmKlWOfOnN+fi4gUoSuL6HRKy37eCA="
+        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      ];
+
+      # Disable that annoying "git tree is dirty" warning.
+      warn-dirty = false;
+
+      auto-optimise-store = true;
+
+      use-xdg-base-directories = true;
+    };
+
+    # Garbage collection.
+    gc.automatic = true;
+
+    # More useful repl.
+    environment.systemPackages = let
+      nrepl =
+        pkgs.writeShellScriptBin "nrepl"
+        # sh
+        ''
+          nix repl "${toString ./.}/repl.nix" "$@"
+        '';
+    in [
+      nrepl
+    ];
+  };
+}
diff --git a/modules/darwin/base/default.nix b/modules/darwin/base/default.nix
new file mode 100644
index 0000000..3925d83
--- /dev/null
+++ b/modules/darwin/base/default.nix
@@ -0,0 +1,5 @@
+{
+  imports = [
+    ./nix.nix
+  ];
+}
diff --git a/modules/darwin/base/nix.nix b/modules/darwin/base/nix.nix
new file mode 100644
index 0000000..335aa2e
--- /dev/null
+++ b/modules/darwin/base/nix.nix
@@ -0,0 +1,9 @@
+{
+  nix = {
+    settings = {
+      trusted-users = [
+        "@darwin"
+      ];
+    };
+  };
+}
diff --git a/modules/darwin/default.nix b/modules/darwin/default.nix
index 3536ae5..e12f3d1 100644
--- a/modules/darwin/default.nix
+++ b/modules/darwin/default.nix
@@ -1,5 +1,6 @@
 {
   imports = [
     ../base
+    ./base
   ];
 }
diff --git a/modules/nixos/base/nix.nix b/modules/nixos/base/nix.nix
index ec7525e..490a284 100644
--- a/modules/nixos/base/nix.nix
+++ b/modules/nixos/base/nix.nix
@@ -1,12 +1,7 @@
-{pkgs, ...}: {
+{
   nix = {
-    package = pkgs.lix;
-
     settings = {
-      experimental-features = ["nix-command" "flakes"];
-
       trusted-users = [
-        "root"
         "@wheel"
       ];
     };
diff --git a/snowflake/modules/darwin/base/nix/default.nix b/snowflake/modules/darwin/base/nix/default.nix
deleted file mode 100644
index f7cf3bc..0000000
--- a/snowflake/modules/darwin/base/nix/default.nix
+++ /dev/null
@@ -1,9 +0,0 @@
-{
-  pkgs,
-  ...
-}:
-{
-  config.nix = {
-    package = pkgs.lix;
-  };
-}
diff --git a/snowflake/modules/home/base/nix/default.nix b/snowflake/modules/home/base/nix/default.nix
deleted file mode 100644
index 8cadd7e..0000000
--- a/snowflake/modules/home/base/nix/default.nix
+++ /dev/null
@@ -1,77 +0,0 @@
-{
-  pkgs,
-  inputs,
-  config,
-  lib,
-  ...
-}: {
-  config = {
-    nix = {
-      package = lib.mkForce pkgs.lix;
-
-      # Pin system <nixpkgs> to flake nixpkgs version.
-      # i.e. for use in pkgs = import <nixpkgs> {}.
-      nixPath = ["nixpkgs=${inputs.nixpkgs}"];
-
-      # Pin flake registry nixpkgs to flake nixpkgs version.
-      # i.e. for use in nix search nixpkgs.
-      registry = {
-        nixpkgs.flake = inputs.nixpkgs;
-      };
-
-      settings = {
-        trusted-users = [
-          "root"
-          "@wheel"
-        ];
-
-        # Enable flakes.
-        experimental-features = [
-          "nix-command"
-          "flakes"
-        ];
-
-        # Set up caches.
-        extra-substituters = [
-          "https://marleyos.cachix.org"
-          "https://nix-community.cachix.org"
-        ];
-
-        trusted-public-keys = [
-          "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
-          "marleyos.cachix.org-1:q2kEtqvS5CoQ8BmKlWOfOnN+fi4gUoSuL6HRKy37eCA="
-          "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
-        ];
-
-        # Disable that annoying "git tree is dirty" warning.
-        warn-dirty = false;
-
-        auto-optimise-store = true;
-      };
-
-      # Garbage collection.
-      gc.automatic = true;
-    };
-
-    nixpkgs.config.import = "${config.xdg.configHome}/nixpkgs/config.nix";
-
-    xdg.configFile."nixpkgs/config.nix".text =
-      # nix
-      ''
-        {
-          allowUnfree = true;
-        }
-      '';
-
-    home.packages = let
-      nrepl =
-        pkgs.writeShellScriptBin "nrepl"
-        # sh
-        ''
-          nix repl "${toString ./.}/repl.nix" "$@"
-        '';
-    in [
-      nrepl
-    ];
-  };
-}