diff --git a/modules/system/system.mod.nix b/modules/system/system.mod.nix
new file mode 100644
index 0000000..3a8451e
--- /dev/null
+++ b/modules/system/system.mod.nix
@@ -0,0 +1,9 @@
+{config, ...}: let
+  machine-id = builtins.substring 0 32 (builtins.hashString "sha256" config.networking.hostName);
+in {
+  system = {
+    # My state version.
+    stateVersion = "23.11";
+  };
+  environment.etc."machine-id".text = "${machine-id}\n";
+}