From cb08d3dd72f51fd20d26c823204faa11d742cfe1 Mon Sep 17 00:00:00 2001
From: nikstur <nikstur@outlook.com>
Date: Tue, 17 Oct 2023 21:39:51 +0200
Subject: [PATCH] nixos/nix-channel: replace activationScript via tmpfiles

---
 nixos/modules/config/nix-channel.nix   | 11 ++++-------
 nixos/tests/activation/nix-channel.nix | 16 ++++++++++++++++
 nixos/tests/all-tests.nix              |  1 +
 3 files changed, 21 insertions(+), 7 deletions(-)
 create mode 100644 nixos/tests/activation/nix-channel.nix

diff --git a/nixos/modules/config/nix-channel.nix b/nixos/modules/config/nix-channel.nix
index 3f8e088ede92..4abc846b0858 100644
--- a/nixos/modules/config/nix-channel.nix
+++ b/nixos/modules/config/nix-channel.nix
@@ -97,12 +97,9 @@ in
 
     nix.settings.nix-path = mkIf (! cfg.channel.enable) (mkDefault "");
 
-    system.activationScripts.nix-channel = mkIf cfg.channel.enable
-      (stringAfter [ "etc" "users" ] ''
-        # Subscribe the root user to the NixOS channel by default.
-        if [ ! -e "/root/.nix-channels" ]; then
-            echo "${config.system.defaultChannel} nixos" > "/root/.nix-channels"
-        fi
-      '');
+    systemd.tmpfiles.rules = lib.mkIf cfg.channel.enable [
+      "f /root/.nix-channels -"
+      ''w "/root/.nix-channels" - - - - "${config.system.defaultChannel} nixos\n"''
+    ];
   };
 }
diff --git a/nixos/tests/activation/nix-channel.nix b/nixos/tests/activation/nix-channel.nix
new file mode 100644
index 000000000000..8416ff0347ac
--- /dev/null
+++ b/nixos/tests/activation/nix-channel.nix
@@ -0,0 +1,16 @@
+{ lib, ... }:
+
+{
+
+  name = "activation-nix-channel";
+
+  meta.maintainers = with lib.maintainers; [ nikstur ];
+
+  nodes.machine = {
+    nix.channel.enable = true;
+  };
+
+  testScript = ''
+    print(machine.succeed("cat /root/.nix-channels"))
+  '';
+}
diff --git a/nixos/tests/all-tests.nix b/nixos/tests/all-tests.nix
index c92acdebcc85..69f1b912d6b3 100644
--- a/nixos/tests/all-tests.nix
+++ b/nixos/tests/all-tests.nix
@@ -265,6 +265,7 @@ in {
   etc = pkgs.callPackage ../modules/system/etc/test.nix { inherit evalMinimalConfig; };
   activation = pkgs.callPackage ../modules/system/activation/test.nix { };
   activation-var = runTest ./activation/var.nix;
+  activation-nix-channel = runTest ./activation/nix-channel.nix;
   etcd = handleTestOn ["x86_64-linux"] ./etcd.nix {};
   etcd-cluster = handleTestOn ["x86_64-linux"] ./etcd-cluster.nix {};
   etebase-server = handleTest ./etebase-server.nix {};