nixos/switch-to-configuration: Allow activation scripts to restart units

The primary use case is tools like sops-nix and agenix to restart units
when secrets change. There's probably other reasons to restart units as
well and a nice thing to have in general.

1 files changed, 73 insertions, 0 deletions

diff --git a/nixos/tests/restart-by-activation-script.nix b/nixos/tests/restart-by-activation-script.nix
new file mode 100644
index 0000000000000..0eec292ea9e2b
--- /dev/null
+++ b/nixos/tests/restart-by-activation-script.nix
@@ -0,0 +1,73 @@
+import ./make-test-python.nix ({ pkgs, ...} : {
+  name = "restart-by-activation-script";
+  meta = with pkgs.lib.maintainers; {
+    maintainers = [ das_j ];
+  };
+
+  machine = { pkgs, ... }: {
+    imports = [ ../modules/profiles/minimal.nix ];
+
+    systemd.services.restart-me = {
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
+        ExecStart = "${pkgs.coreutils}/bin/true";
+      };
+    };
+
+    systemd.services.reload-me = {
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = rec {
+        Type = "oneshot";
+        RemainAfterExit = true;
+        ExecStart = "${pkgs.coreutils}/bin/true";
+        ExecReload = ExecStart;
+      };
+    };
+
+    system.activationScripts.test = {
+      supportsDryActivation = true;
+      text = ''
+        if [ -e /test-the-activation-script ]; then
+          if [ "$NIXOS_ACTION" != dry-activate ]; then
+            touch /activation-was-run
+            echo restart-me.service > /run/nixos/activation-restart-list
+            echo reload-me.service > /run/nixos/activation-reload-list
+          else
+            echo restart-me.service > /run/nixos/dry-activation-restart-list
+            echo reload-me.service > /run/nixos/dry-activation-reload-list
+          fi
+        fi
+      '';
+    };
+  };
+
+  testScript = /* python */ ''
+    machine.wait_for_unit("multi-user.target")
+
+    with subtest("nothing happens when the activation script does nothing"):
+        out = machine.succeed("/run/current-system/bin/switch-to-configuration dry-activate 2>&1")
+        assert 'restart' not in out
+        assert 'reload' not in out
+        out = machine.succeed("/run/current-system/bin/switch-to-configuration test")
+        assert 'restart' not in out
+        assert 'reload' not in out
+
+    machine.succeed("touch /test-the-activation-script")
+
+    with subtest("dry activation"):
+        out = machine.succeed("/run/current-system/bin/switch-to-configuration dry-activate 2>&1")
+        assert 'would restart the following units: restart-me.service' in out
+        assert 'would reload the following units: reload-me.service' in out
+        machine.fail("test -f /run/nixos/dry-activation-restart-list")
+        machine.fail("test -f /run/nixos/dry-activation-reload-list")
+
+    with subtest("real activation"):
+        out = machine.succeed("/run/current-system/bin/switch-to-configuration test 2>&1")
+        assert 'restarting the following units: restart-me.service' in out
+        assert 'reloading the following units: reload-me.service' in out
+        machine.fail("test -f /run/nixos/activation-restart-list")
+        machine.fail("test -f /run/nixos/activation-reload-list")
+  '';
+})