fix restart failing under non-root

restart_frigate() called psutil.Process(1).terminate() to signal s6-svscan, but s6-svscan runs as root while frigate runs as uid 1000, so the call raised AccessDenied. That exception escaped every caller: the UI restart button dropped its websocket client, MQTT restart and Save & Restart just logged and did nothing, and the watchdog crashed its own monitoring thread on a dead detector. This catches AccessDenied and falls through to the existing SIGINT branch, which exits the process for s6 to restart it.

frigate/test/test_restart_frigate.py

@@ -0,0 +1,55 @@
+"""Tests for restarting frigate under s6."""
+
+import signal
+import unittest
+from unittest.mock import MagicMock, patch
+
+import psutil
+
+from frigate.util.services import restart_frigate
+
+
+class TestRestartFrigate(unittest.TestCase):
+    def _s6_process(self) -> MagicMock:
+        proc = MagicMock()
+        proc.name.return_value = "s6-svscan"
+        return proc
+
+    @patch("frigate.util.services.os.kill")
+    @patch("frigate.util.services.psutil.Process")
+    def test_terminates_s6_when_permitted(self, mock_process, mock_kill):
+        proc = self._s6_process()
+        mock_process.return_value = proc
+
+        restart_frigate()
+
+        proc.terminate.assert_called_once()
+        mock_kill.assert_not_called()
+
+    @patch("frigate.util.services.os.getpid", return_value=99)
+    @patch("frigate.util.services.os.kill")
+    @patch("frigate.util.services.psutil.Process")
+    def test_exits_self_when_s6_signal_is_denied(
+        self, mock_process, mock_kill, _mock_getpid
+    ):
+        """Running unprivileged, frigate cannot signal root's s6-svscan."""
+        proc = self._s6_process()
+        proc.terminate.side_effect = psutil.AccessDenied(pid=1, name="s6-svscan")
+        mock_process.return_value = proc
+
+        restart_frigate()
+
+        mock_kill.assert_called_once_with(99, signal.SIGINT)
+
+    @patch("frigate.util.services.os.getpid", return_value=99)
+    @patch("frigate.util.services.os.kill")
+    @patch("frigate.util.services.psutil.Process")
+    def test_exits_self_without_s6(self, mock_process, mock_kill, _mock_getpid):
+        proc = MagicMock()
+        proc.name.return_value = "init"
+        mock_process.return_value = proc
+
+        restart_frigate()
+
+        proc.terminate.assert_not_called()
+        mock_kill.assert_called_once_with(99, signal.SIGINT)

frigate/util/services.py

@@ -35,12 +35,19 @@ logger = logging.getLogger(__name__)
 
 def restart_frigate():
     proc = psutil.Process(1)
+
     # if this is running via s6, sigterm pid 1
     if proc.name() == "s6-svscan":
-        proc.terminate()
+        try:
+            proc.terminate()
+            return
+        except psutil.AccessDenied:
+            # frigate runs unprivileged, so it cannot signal root's s6-svscan.
+            # exiting this process instead runs frigate/finish, which halts s6
+            logger.debug("Not permitted to signal s6-svscan, exiting instead")
+
     # otherwise, just try and exit frigate
-    else:
-        os.kill(os.getpid(), signal.SIGINT)
+    os.kill(os.getpid(), signal.SIGINT)
 
 
 def print_stack(sig, frame):