nixos/stage-2-init: remove 'readOnlyNixStore' option

The `boot.readOnlyNixStore` option can be removed,
now that the more flexible `boot.nixStoreMountOpts` option exists.

doc/release-notes/rl-2511.section.md

@@ -9,7 +9,7 @@
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
-- Create the first release note entry in this section!
+- The `boot.readOnlyNixStore` has been removed. Control over bind mount options on `/nix/store` is now offered by the `boot.nixStoreMountOpts` option.
 
 ## Other Notable Changes {#sec-nixpkgs-release-25.11-notable-changes}
 

nixos/modules/system/boot/stage-2.nix

@@ -39,6 +39,16 @@ let
 in
 
 {
+  imports = [
+    (lib.mkRemovedOptionModule
+      [
+        "boot"
+        "readOnlyNixStore"
+      ]
+      "Please use the `boot.nixStoreMountOpts' option to define mount options for the Nix store, including 'ro'"
+    )
+  ];
+
   options = {
 
     boot = {
@@ -52,17 +62,6 @@ in
         '';
       };
 
-      readOnlyNixStore = mkOption {
-        type = types.bool;
-        default = true;
-        description = ''
-          If set, NixOS will enforce the immutability of the Nix store
-          by making {file}`/nix/store` a read-only bind
-          mount. Nix will automatically make the store writable when
-          needed.
-        '';
-      };
-
       nixStoreMountOpts = mkOption {
         type = types.listOf types.nonEmptyStr;
         default = [
@@ -103,9 +102,5 @@ in
   config = {
 
     system.build.bootStage2 = bootStage2;
-    boot.nixStoreMountOpts = [
-      "nodev"
-      "nosuid"
-    ] ++ lib.optional config.boot.readOnlyNixStore "ro";
   };
 }