Add common configuration file.

nodes/common/configuration.nix

@@ -0,0 +1,19 @@
+{ pkgs, ... }:
+{
+  nixpkgs = {
+    config.allowUnfree = true;
+  };
+  nix = {
+    optimize.automatic = true;
+    extraOptions = ''
+      experimental-features = nix-command flakes
+    '';
+  };
+
+  users.users = {
+    jay = {
+      description = "Jay Carter";
+      shell = pkgs.bash;
+    };
+  };
+}