From 78a3174238c13e6d65e437bdda08c1fbb8d78a51 Mon Sep 17 00:00:00 2001
From: Josh Hawkins <32435876+hawkeye217@users.noreply.github.com>
Date: Mon, 9 Nov 2026 14:11:04 -0600
Subject: [PATCH] keep config owner and handle file bind mounts in migration
 writes

os.replace failed with EBUSY when config.yml was a file bind mount, as in the documented --validate-config command, and the replaced file lost its original owner when Frigate ran as root. The write now copies in place on EBUSY and restores the original owner when permitted. Tests cover a failed dump leaving the original config and the bind-mount fallback.
---
 frigate/test/test_config_migration.py | 25 +++++++++++++++++++++++++
 frigate/util/config.py                | 19 +++++++++++++++++--
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/frigate/test/test_config_migration.py b/frigate/test/test_config_migration.py
index c33aa95425..dd682c4e38 100644
--- a/frigate/test/test_config_migration.py
+++ b/frigate/test/test_config_migration.py
@@ -1,5 +1,6 @@
 """Tests for migrating detectors and model into the models list."""
 
+import errno
 import logging
 import os
 import tempfile
@@ -240,6 +241,30 @@ class TestMigrateConfigFile(unittest.TestCase):
         with open(self.config_file) as f:
             return YAML().load(f)
 
+    def test_a_failed_write_leaves_the_original_config(self):
+        original = "mqtt:\n  enabled: false\ncameras: {}\n"
+        with open(self.config_file, "w") as f:
+            f.write(original)
+
+        with (
+            patch.object(YAML, "dump", side_effect=RuntimeError),
+            self.assertRaises(RuntimeError),
+        ):
+            migrate_frigate_config(self.config_file)
+
+        with open(self.config_file) as f:
+            self.assertEqual(f.read(), original)
+
+    def test_a_file_bind_mount_is_written_in_place(self):
+        with patch(
+            "frigate.util.config.os.replace",
+            side_effect=OSError(errno.EBUSY, "Device or resource busy"),
+        ):
+            migrated = self._migrate("mqtt:\n  enabled: false\ncameras: {}\n")
+
+        self.assertEqual(migrated["version"], CURRENT_CONFIG_VERSION)
+        self.assertFalse(os.path.exists(f"{self.config_file}.tmp"))
+
     def test_migrates_a_config_already_stamped_with_the_current_version(self):
         # 0.19 is unreleased, so a dev config can be current and still use
         # the pre-models keys
diff --git a/frigate/util/config.py b/frigate/util/config.py
index 1555a903b4..7c83edf793 100644
--- a/frigate/util/config.py
+++ b/frigate/util/config.py
@@ -1,6 +1,8 @@
 """configuration utils."""
 
 import asyncio
+import contextlib
+import errno
 import ipaddress
 import logging
 import os
@@ -213,11 +215,24 @@ def find_config_file() -> str:
 
 
 def _write_config(config_file: str, yaml: YAML, config: dict[str, Any]) -> None:
+    st = os.stat(config_file)
     tmp_file = f"{config_file}.tmp"
     with open(tmp_file, "w") as f:
         yaml.dump(config, f)
-    shutil.copymode(config_file, tmp_file)
-    os.replace(tmp_file, config_file)
+    os.chmod(tmp_file, st.st_mode)
+
+    with contextlib.suppress(PermissionError):
+        os.chown(tmp_file, st.st_uid, st.st_gid)
+
+    try:
+        os.replace(tmp_file, config_file)
+    except OSError as e:
+        if e.errno != errno.EBUSY:
+            raise
+
+        # a file bind mount can't be renamed over, so write it in place
+        shutil.copyfile(tmp_file, config_file)
+        os.remove(tmp_file)
 
 
 def migrate_frigate_config(config_file: str):