From 7d0b5b3a94afcb751e4e79ec83f9ee8e3c5b8a0b Mon Sep 17 00:00:00 2001
From: nikstur <nikstur@outlook.com>
Date: Wed, 1 Nov 2023 16:01:49 +0100
Subject: [PATCH] nixos/nix-channnel: fix setting up the default channel again

---
 nixos/modules/config/nix-channel.nix   | 3 +--
 nixos/tests/activation/nix-channel.nix | 9 +++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/nixos/modules/config/nix-channel.nix b/nixos/modules/config/nix-channel.nix
index 0565c9cc8dad..a7ca7a5c74a4 100644
--- a/nixos/modules/config/nix-channel.nix
+++ b/nixos/modules/config/nix-channel.nix
@@ -98,8 +98,7 @@ in
     nix.settings.nix-path = mkIf (! cfg.channel.enable) (mkDefault "");
 
     systemd.tmpfiles.rules = lib.mkIf cfg.channel.enable [
-      "f /root/.nix-channels -"
-      ''w+ "/root/.nix-channels" - - - - ${config.system.defaultChannel} nixos\n''
+      ''f /root/.nix-channels - - - - ${config.system.defaultChannel} nixos\n''
     ];
   };
 }
diff --git a/nixos/tests/activation/nix-channel.nix b/nixos/tests/activation/nix-channel.nix
index a01a66ebc1bf..d26ea98e56cc 100644
--- a/nixos/tests/activation/nix-channel.nix
+++ b/nixos/tests/activation/nix-channel.nix
@@ -11,7 +11,16 @@
   };
 
   testScript = { nodes, ... }: ''
+    machine.start(allow_reboot=True)
+
     assert machine.succeed("cat /root/.nix-channels") == "${nodes.machine.system.defaultChannel} nixos\n"
+
+    nixpkgs_unstable_channel = "https://nixos.org/channels/nixpkgs-unstable nixpkgs"
+    machine.succeed(f"echo '{nixpkgs_unstable_channel}' > /root/.nix-channels")
+
+    machine.reboot()
+
+    assert machine.succeed("cat /root/.nix-channels") == f"{nixpkgs_unstable_channel}\n"
   '';
 
 }