From 65ff0d5f9de3e8f0ca5ec3a70549e30afd84a6d5 Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Tue, 22 Aug 2017 15:04:18 +0300
Subject: [PATCH 1/2] switch-to-configuration: fix detection of changes between
 rebuilds for template instances

This makes declarative containers truly reloadable. Current code already declares it:

https://github.com/NixOS/nixpkgs/blob/56904d7c423f2b13b37fbd29f39bbb4b52bc7824/nixos/modules/virtualisation/containers.nix#L488

```
  restartIfChanged = false;
```

https://github.com/NixOS/nixpkgs/blob/56904d7c423f2b13b37fbd29f39bbb4b52bc7824/nixos/modules/virtualisation/containers.nix#L540

```
  reloadIfChanged = true;
```

Original author: @chrisfarms in https://github.com/NixOS/nixpkgs/pull/3021/commits/6e36619b277f78ece1bb81b79b5651897e46a2bf
Most of stuff from that commit has already been ported.
---
 .../modules/system/activation/switch-to-configuration.pl | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/nixos/modules/system/activation/switch-to-configuration.pl b/nixos/modules/system/activation/switch-to-configuration.pl
index 88e7847cf8c8..29cc60b00324 100644
--- a/nixos/modules/system/activation/switch-to-configuration.pl
+++ b/nixos/modules/system/activation/switch-to-configuration.pl
@@ -147,11 +147,16 @@ my $activePrev = getActiveUnits;
 while (my ($unit, $state) = each %{$activePrev}) {
     my $baseUnit = $unit;
 
-    # Recognise template instances.
-    $baseUnit = "$1\@.$2" if $unit =~ /^(.*)@[^\.]*\.(.*)$/;
     my $prevUnitFile = "/etc/systemd/system/$baseUnit";
     my $newUnitFile = "$out/etc/systemd/system/$baseUnit";
 
+    # Detect template instances.
+    if (!-e $prevUnitFile && !-e $newUnitFile && $unit =~ /^(.*)@[^\.]*\.(.*)$/) {
+      $baseUnit = "$1\@.$2";
+      $prevUnitFile = "/etc/systemd/system/$baseUnit";
+      $newUnitFile = "$out/etc/systemd/system/$baseUnit";
+    }
+
     my $baseName = $baseUnit;
     $baseName =~ s/\.[a-z]*$//;
 

From 63f8122cd93b8d100865515d80b5e1325e69f2cd Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Wed, 23 Aug 2017 12:43:07 +0300
Subject: [PATCH 2/2] nixos tests: add test for declarative containers, that
 container config changes are applied on `nixos-rebuild switch` invocations.

---
 nixos/tests/containers-reloadable.nix | 66 +++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 nixos/tests/containers-reloadable.nix

diff --git a/nixos/tests/containers-reloadable.nix b/nixos/tests/containers-reloadable.nix
new file mode 100644
index 000000000000..b5867c6f6ab1
--- /dev/null
+++ b/nixos/tests/containers-reloadable.nix
@@ -0,0 +1,66 @@
+import ./make-test.nix ({ pkgs, lib, ...} :
+let
+  client_base = rec {
+    
+    containers.test1 = {
+      autoStart = true;
+      config = {
+        environment.etc."check".text = "client_base";
+      };
+    };
+
+    # prevent make-test.nix to change IP
+    networking.interfaces = {
+      eth1.ip4 = lib.mkOverride 0 [ ];
+    };
+  };
+in {
+  name = "cotnainers-reloadable";
+  meta = with pkgs.stdenv.lib.maintainers; {
+    maintainers = [ danbst ];
+  };
+
+  nodes = {
+    client = { lib, pkgs, ... }: {
+      imports = [ client_base ];
+    };
+
+    client_c1 = { lib, pkgs, ... }: {
+      imports = [ client_base ];
+
+      containers.test1.config = {
+        environment.etc."check".text = lib.mkForce "client_c1";
+        services.httpd.enable = true;
+        services.httpd.adminAddr = "nixos@example.com";
+      };
+    };
+    client_c2 = { lib, pkgs, ... }: {
+      imports = [ client_base ];
+
+      containers.test1.config = {
+        environment.etc."check".text = lib.mkForce "client_c2";
+        services.nginx.enable = true;
+      };
+    };
+  };
+
+  testScript = {nodes, ...}: let
+    originalSystem = nodes.client.config.system.build.toplevel;
+    c1System = nodes.client_c1.config.system.build.toplevel;
+    c2System = nodes.client_c2.config.system.build.toplevel;
+  in ''
+    $client->start();
+    $client->waitForUnit("default.target");
+    $client->succeed("[[ \$(nixos-container run test1 cat /etc/check) == client_base ]] >&2");
+
+    $client->succeed("${c1System}/bin/switch-to-configuration test >&2");
+    $client->succeed("[[ \$(nixos-container run test1 cat /etc/check) == client_c1 ]] >&2");
+    $client->succeed("systemctl status httpd -M test1 >&2");
+
+    $client->succeed("${c2System}/bin/switch-to-configuration test >&2");
+    $client->succeed("[[ \$(nixos-container run test1 cat /etc/check) == client_c2 ]] >&2");
+    $client->fail("systemctl status httpd -M test1 >&2");
+    $client->succeed("systemctl status nginx -M test1 >&2");
+  '';
+
+})