3p/nixpkgs: allow disabling nix in nixos

third_party/nixpkgs/nixos/modules/installer/tools/tools.nix

@@ -91,7 +91,7 @@ in
     '';
   };
 
-  config = {
+  config = mkIf config.nix.enable {
 
     system.nixos-generate-config.configuration = mkDefault ''
       # Edit this configuration file to define what should be installed on

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

@@ -81,6 +81,14 @@ in
 
     nix = {
 
+      enable = mkOption {
+        type = types.bool;
+        default = true;
+        description = ''
+          If disabled, Nix will not be available on the built NixOS system.
+        '';
+      };
+
       package = mkOption {
         type = types.package;
         default = pkgs.nix;
@@ -498,7 +506,7 @@ in
 
   ###### implementation
 
-  config = {
+  config = mkIf cfg.enable {
 
     assertions = [
       {

third_party/nixpkgs/nixos/modules/services/misc/nix-gc.nix

@@ -48,7 +48,7 @@ in
 
   ###### implementation
 
-  config = {
+  config = mkIf config.nix.enable {
 
     systemd.services.nix-gc =
       { description = "Nix Garbage Collector";

third_party/nixpkgs/nixos/modules/services/misc/nix-optimise.nix

@@ -36,7 +36,7 @@ in
 
   ###### implementation
 
-  config = {
+  config = mkIf config.nix.enable {
 
     systemd.services.nix-optimise =
       { description = "Nix Store Optimiser";

third_party/nixpkgs/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py

@@ -124,18 +124,19 @@ def mkdir_p(path):
             raise
 
 def get_generations(profile=None):
-    gen_list = subprocess.check_output([
+    generation_dir = "/nix/var/nix/profiles/%s" % ("system-profiles" if profile else "",)
-        "@nix@/bin/nix-env",
+    profile_name = profile if profile else "system"
-        "--list-generations",
+    generations = []
-        "-p",
+    for gen_entry in os.scandir(generation_dir):
-        "/nix/var/nix/profiles/%s" % ("system-profiles/" + profile if profile else "system"),
+        gen_name = gen_entry.name
-        "--option", "build-users-group", ""],
+        if not (gen_name.startswith(profile_name + '-') and gen_name.endswith('-link')):
-        universal_newlines=True)
+            continue
-    gen_lines = gen_list.split('\n')
+        gen_num = gen_name[len(profile_name+'-'):-len('-link')]
-    gen_lines.pop()
+        generations.append(int(gen_num))
+    generations.sort()
 
     configurationLimit = @configurationLimit@
-    return [ (profile, int(line.split()[0])) for line in gen_lines ][-configurationLimit:]
+    return [ (profile, gen_num) for gen_num in sorted(generations) ][-configurationLimit:]
 
 def remove_old_entries(gens):
     rex_profile = re.compile("^@efiSysMountPoint@/loader/entries/nixos-(.*)-generation-.*\.conf$")

third_party/nixpkgs/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix

@@ -16,8 +16,6 @@ let
 
     systemd = config.systemd.package;
 
-    nix = config.nix.package.out;
-
     timeout = if config.boot.loader.timeout != null then config.boot.loader.timeout else "";
 
     editor = if cfg.editor then "True" else "False";

third_party/nixpkgs/patches/0001-nixpkgs-allow-disable-nix.patch

@@ -0,0 +1,108 @@
+diff --git a/nixos/modules/installer/tools/tools.nix b/nixos/modules/installer/tools/tools.nix
+--- a/nixos/modules/installer/tools/tools.nix
++++ b/nixos/modules/installer/tools/tools.nix
+@@ -86,7 +86,7 @@ in
+     '';
+   };
+ 
+-  config = {
++  config = mkIf config.nix.enable {
+ 
+     system.nixos-generate-config.configuration = mkDefault ''
+       # Edit this configuration file to define what should be installed on
+diff --git a/nixos/modules/services/misc/nix-daemon.nix b/nixos/modules/services/misc/nix-daemon.nix
+--- a/nixos/modules/services/misc/nix-daemon.nix
++++ b/nixos/modules/services/misc/nix-daemon.nix
+@@ -81,6 +81,14 @@ in
+ 
+     nix = {
+ 
++      enable = mkOption {
++        type = types.bool;
++        default = true;
++        description = ''
++          If disabled, Nix will not be available on the built NixOS system.
++        '';
++      };
++
+       package = mkOption {
+         type = types.package;
+         default = pkgs.nix;
+@@ -498,7 +506,7 @@ in
+ 
+   ###### implementation
+ 
+-  config = {
++  config = mkIf cfg.enable {
+ 
+     nix.binaryCachePublicKeys = [ "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" ];
+     nix.binaryCaches = [ "https://cache.nixos.org/" ];
+diff --git a/nixos/modules/services/misc/nix-gc.nix b/nixos/modules/services/misc/nix-gc.nix
+--- a/nixos/modules/services/misc/nix-gc.nix
++++ b/nixos/modules/services/misc/nix-gc.nix
+@@ -48,7 +48,7 @@ in
+ 
+   ###### implementation
+ 
+-  config = {
++  config = mkIf config.nix.enable {
+ 
+     systemd.services.nix-gc =
+       { description = "Nix Garbage Collector";
+diff --git a/nixos/modules/services/misc/nix-optimise.nix b/nixos/modules/services/misc/nix-optimise.nix
+--- a/nixos/modules/services/misc/nix-optimise.nix
++++ b/nixos/modules/services/misc/nix-optimise.nix
+@@ -36,7 +36,7 @@ in
+ 
+   ###### implementation
+ 
+-  config = {
++  config = mkIf config.nix.enable {
+ 
+     systemd.services.nix-optimise =
+       { description = "Nix Store Optimiser";
+diff --git a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py
+--- a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py
++++ b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py
+@@ -124,18 +124,19 @@ def mkdir_p(path):
+             raise
+ 
+ def get_generations(profile=None):
+-    gen_list = subprocess.check_output([
+-        "@nix@/bin/nix-env",
+-        "--list-generations",
+-        "-p",
+-        "/nix/var/nix/profiles/%s" % ("system-profiles/" + profile if profile else "system"),
+-        "--option", "build-users-group", ""],
+-        universal_newlines=True)
+-    gen_lines = gen_list.split('\n')
+-    gen_lines.pop()
++    generation_dir = "/nix/var/nix/profiles/%s" % ("system-profiles" if profile else "",)
++    profile_name = profile if profile else "system"
++    generations = []
++    for gen_entry in os.scandir(generation_dir):
++        gen_name = gen_entry.name
++        if not (gen_name.startswith(profile_name + '-') and gen_name.endswith('-link')):
++            continue
++        gen_num = gen_name[len(profile_name+'-'):-len('-link')]
++        generations.append(int(gen_num))
++    generations.sort()
+ 
+     configurationLimit = @configurationLimit@
+-    return [ (profile, int(line.split()[0])) for line in gen_lines ][-configurationLimit:]
++    return [ (profile, gen_num) for gen_num in sorted(generations) ][-configurationLimit:]
+ 
+ def remove_old_entries(gens):
+     rex_profile = re.compile("^@efiSysMountPoint@/loader/entries/nixos-(.*)-generation-.*\.conf$")
+diff --git a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix
+--- a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix
++++ b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix
+@@ -16,8 +16,6 @@ let
+ 
+     systemd = config.systemd.package;
+ 
+-    nix = config.nix.package.out;
+-
+     timeout = if config.boot.loader.timeout != null then config.boot.loader.timeout else "";
+ 
+     editor = if cfg.editor then "True" else "False";