Merge pull request #120565 from Ericson2314/nixos-without-nix

nixos/nix-daemon: Add enable option

nixos/modules/services/misc/nix-daemon.nix

@@ -82,6 +82,15 @@ in
 
     nix = {
 
+      enable = mkOption {
+        type = types.bool;
+        default = true;
+        description = ''
+          Whether to enable Nix.
+          Disabling Nix makes the system hard to modify and the Nix programs and configuration will not be made available by NixOS itself.
+        '';
+      };
+
       package = mkOption {
         type = types.package;
         default = pkgs.nix;
@@ -499,7 +508,7 @@ in
 
   ###### implementation
 
-  config = {
+  config = mkIf cfg.enable {
 
     nix.binaryCachePublicKeys = [ "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" ];
     nix.binaryCaches = [ "https://cache.nixos.org/" ];

nixos/tests/all-tests.nix

@@ -478,6 +478,7 @@ in
   wasabibackend = handleTest ./wasabibackend.nix {};
   wiki-js = handleTest ./wiki-js.nix {};
   wireguard = handleTest ./wireguard {};
+  without-nix = handleTest ./without-nix.nix {};
   wmderland = handleTest ./wmderland.nix {};
   wpa_supplicant = handleTest ./wpa_supplicant.nix {};
   wordpress = handleTest ./wordpress.nix {};

nixos/tests/without-nix.nix

@@ -0,0 +1,23 @@
+import ./make-test-python.nix ({ lib, ... }: {
+  name = "without-nix";
+  meta = with lib.maintainers; {
+    maintainers = [ ericson2314 ];
+  };
+
+  nixpkgs.overlays = [
+    (self: super: {
+      nix = throw "don't want to use this";
+    })
+  ];
+
+  nodes.machine = { ... }: {
+    nix.enable = false;
+  };
+
+  testScript = ''
+    start_all()
+
+    machine.succeed("which which")
+    machine.fail("which nix")
+  '';
+})