AutoOptimizeStore changed to new syntax.

extra-nixos.nix

@@ -0,0 +1,23 @@
+{ config, pkgs, ... }:
+{
+
+##### nix extra options #######
+
+  nix = {
+    extraOptions = ''
+      experimental-features = nix-command flakes	
+      keep-outputs = true
+      keep-derivations = true
+    '';
+#    package = pkgs.nixFlakes;
+    gc = {
+      automatic = true;
+      dates = "weekly";
+      options = "--delete-older-than 7d";
+      persistent = true;
+    };
+    settings.auto-optimize-store = true;
+  };
+}
+
+}