tune nix settings

iso.nix

@@ -21,6 +21,32 @@
   # Configure host id for ZFS to work
   networking.hostId = lib.mkDefault "8425e349";
 
+  nix = {
+    settings = {
+      trusted-users = [ "@wheel" ];
+      experimental-features = [ "nix-command" "flakes" "repl-flake" ];
+      auto-optimise-store = true;
+    };
+    extraOptions = ''
+      min-free = ${toString (100 * 1024 * 1024)}
+      max-free = ${toString (1024 * 1024 * 1024)}
+    '';
+    nixPath = lib.mkForce [ "nixpkgs=${lib.cleanSource pkgs.path}" ];
+    registry = lib.mkForce {
+      "nixpkgs" = {
+        from = {
+          type = "indirect";
+          id = "nixpkgs";
+        };
+        to = {
+          type = "path";
+          path = lib.cleanSource pkgs.path;
+        };
+        exact = true;
+      };
+    };
+  };
+
   environment.systemPackages = with pkgs; [
     w3m-nographics # needed for the manual anyway
     testdisk # useful for repairing boot problems