Add modules/nixos/system/default.nix

modules/nixos/system/default.nix

@@ -0,0 +1,49 @@
+{
+  lib,
+  config,
+  inputs,
+  ...
+}: let
+  inherit (lib.attrsets) mapAttrs mapAttrsToList;
+in {
+  config = {
+    # Common Nix Settings, registry thing is specifically for flakes
+    nix = {
+      registry = lib.mkForce (mapAttrs (_: value: {flake = value;}) inputs);
+      nixPath = lib.mkForce (mapAttrsToList (key: value: "${key}=${value.to.path}") config.nix.registry);
+      optimise.automatic = true;
+
+      gc = {
+        automatic = true;
+        options = "--delete-older-than 14d";
+      };
+
+      settings = {
+        experimental-features = "nix-command flakes";
+        warn-dirty = false;
+        keep-derivations = true;
+        keep-env-derivations = true;
+        keep-outputs = true;
+        auto-optimise-store = false;
+
+        substituters = [
+          "https://nix-community.cachix.org"
+          "https://cache.nixos.org/"
+        ];
+
+        trusted-public-keys = [
+          "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+          "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+        ];
+      };
+    };
+
+    nixpkgs = {
+      config.allowUnfree = true;
+
+      overlays = [
+        # overlays if you want them
+      ];
+    };
+  };
+}