fix(backup): restore must not depend on owning the file it replaces

Follow-up from testing the previous commit on real hardware, where the
secrets fix turned out to be both too narrow and slightly wrong.

Too narrow: config.json, wifi_config.json and ytm_auth.json are installed
root-owned and group-readable exactly like the secrets file, so all four
were unrestorable by the web service, not just one. `shutil.copy2` opens
the destination for writing, which needs permission on the *existing
file*; the web user could create files in that directory all day and
still not replace them.

Slightly wrong: the previous commit loosened the secrets file to
group-writable. That was treating the symptom. The real error was
deciding ownership from `ledmatrix.service` -- the display service, which
runs as root and only ever *reads* secrets -- when the account that
*writes* them is the web interface, which deliberately does not run as
root. Ownership now follows the web service's user and the mode stays
640.

`_copy_file` writes a temporary file alongside the target and renames
over it. That needs only directory permission, so a restore no longer
cares who owns the destination, and it is atomic: a crash mid-restore can
no longer leave a half-written config. The destination's mode is carried
across so restoring secrets does not widen them to the umask, and its
owner is carried across too when the OS allows it -- only root can hand a
file to another user, so a restore run by the web service keeps its own
ownership rather than pretending to preserve root's.

Verified on a device with all four config files set root-owned 640 and
unwritable by the web user: before, every one failed with EACCES; after,
the restore reports success with no errors and all four sections
restored, mode still 640, root still able to read them and the web
service still able to write them.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Udr6MfaFLUPhX5Fgo67Jf5

.github/workflows/test.yml

@@ -86,4 +86,6 @@ jobs:
             test/test_template_targets.py \
             test/test_widget_scripts.py \
             test/test_doc_links.py \
+            test/test_registry_id_resolution.py \
+            test/test_backup_manager.py \
             test/web_interface/test_cache.py

README.md

@@ -365,6 +365,12 @@ sudo bash ./first_time_install.sh
 
 This single script installs services, dependencies, configures permissions and sudoers, and validates the setup.
 
+It finishes by asking whether to reboot. If you run it non-interactively — piped, over a script, or with `-y` — there is no one to ask, so **it reboots immediately without prompting**. Pass `--no-reboot-prompt` to install without rebooting:
+
+```bash
+sudo bash ./first_time_install.sh -y --no-reboot-prompt
+```
+
 </details>
 
 </details>

first_time_install.sh

@@ -1480,26 +1480,37 @@ if [ -f "$PROJECT_ROOT_DIR/config/config.json" ]; then
 fi
 
 # Set proper permissions for secrets file (restrictive: owner rw, group r)
-# If service runs as root, set ownership to root so it can read as owner
+# Owned by whoever WRITES the file, which is the web interface.
-# Otherwise, use ACTUAL_USER and rely on group membership
+#
+# This used to read the User= of ledmatrix.service — the display service —
+# and, finding root, hand the file to root:ledmatrix 640. But the display
+# service only ever reads secrets, and root can read any file regardless of
+# mode. The account that *writes* them is the web interface: it saves config
+# edits and performs backup restores, and it deliberately does not run as root
+# (a web server should not). So a root-owned, group-read-only file left the web
+# UI unable to write its own secrets, and restoring a backup failed with
+# "Permission denied: config_secrets.json" while every other file in the same
+# backup restored fine.
+#
+# Owning by the writer keeps the tighter 640 rather than loosening to
+# group-writable, and root still reads it as superuser.
 if [ -f "$PROJECT_ROOT_DIR/config/config_secrets.json" ]; then
-    # Check if service runs as root (from service file or template)
+    # The web service is the writer; fall back to the display service, then to
-    SERVICE_USER="root"
+    # the installing user, so an unusual layout still lands somewhere sensible.
-    if [ -f "/etc/systemd/system/ledmatrix.service" ]; then
+    SECRETS_OWNER=""
-        SERVICE_USER=$(grep "^User=" /etc/systemd/system/ledmatrix.service | cut -d'=' -f2 || echo "root")
+    for unit in "/etc/systemd/system/ledmatrix-web.service" \
-    elif [ -f "$PROJECT_ROOT_DIR/systemd/ledmatrix.service" ]; then
+                "$PROJECT_ROOT_DIR/systemd/ledmatrix-web.service"; do
-        SERVICE_USER=$(grep "^User=" "$PROJECT_ROOT_DIR/systemd/ledmatrix.service" | cut -d'=' -f2 || echo "root")
+        if [ -f "$unit" ]; then
+            SECRETS_OWNER=$(grep -m1 "^User=" "$unit" | cut -d'=' -f2)
+            [ -n "$SECRETS_OWNER" ] && break
         fi
-    
+    done
-    if [ "$SERVICE_USER" = "root" ]; then
+    if [ -z "$SECRETS_OWNER" ]; then
-        # Service runs as root - set ownership to root so it can read as owner
+        SECRETS_OWNER="$ACTUAL_USER"
-        chown "root:$LEDMATRIX_GROUP" "$PROJECT_ROOT_DIR/config/config_secrets.json" || true
-        echo "✓ Secrets file permissions set (root:ledmatrix for root service)"
-    else
-        # Service runs as regular user - use ACTUAL_USER and rely on group membership
-        chown "$ACTUAL_USER:$LEDMATRIX_GROUP" "$PROJECT_ROOT_DIR/config/config_secrets.json" || true
-        echo "✓ Secrets file permissions set ($ACTUAL_USER:ledmatrix)"
     fi
+    # A root-owned file is only correct when the writer really is root.
+    chown "$SECRETS_OWNER:$LEDMATRIX_GROUP" "$PROJECT_ROOT_DIR/config/config_secrets.json" || true
+    echo "✓ Secrets file owned by the web service user ($SECRETS_OWNER:$LEDMATRIX_GROUP, mode 640)"
     chmod 640 "$PROJECT_ROOT_DIR/config/config_secrets.json"
 fi
 

src/backup_manager.py

@@ -16,6 +16,7 @@ import json
 import logging
 import os
 import shutil
+import stat
 import socket
 import tempfile
 import zipfile
@@ -82,6 +83,10 @@ BUNDLED_FONTS: frozenset[str] = frozenset({
 _CONFIG_REL = Path("config/config.json")
 _SECRETS_REL = Path("config/config_secrets.json")
 _WIFI_REL = Path("config/wifi_config.json")
+# Sits in config/ next to the three above and is pure user state — a
+# YouTube Music session that has to be re-authenticated by hand if lost.
+# It was omitted from backups, so a restore silently signed the user out.
+_YTM_REL = Path("config/ytm_auth.json")
 _FONTS_REL = Path("assets/fonts")
 _PLUGIN_UPLOADS_REL = Path("assets/plugins")
 _STATE_REL = Path("data/plugin_state.json")
@@ -303,6 +308,9 @@ def create_backup(
             if (project_root / _WIFI_REL).exists():
                 zf.write(project_root / _WIFI_REL, _WIFI_REL.as_posix())
                 contents.append("wifi")
+            if (project_root / _YTM_REL).exists():
+                zf.write(project_root / _YTM_REL, _YTM_REL.as_posix())
+                contents.append("ytm_auth")
 
             # User-uploaded fonts.
             user_fonts = iter_user_fonts(project_root)
@@ -348,6 +356,7 @@ def preview_backup_contents(project_root: Path) -> Dict[str, Any]:
         "has_config": (project_root / _CONFIG_REL).exists(),
         "has_secrets": (project_root / _SECRETS_REL).exists(),
         "has_wifi": (project_root / _WIFI_REL).exists(),
+        "has_ytm_auth": (project_root / _YTM_REL).exists(),
         "user_fonts": [p.name for p in iter_user_fonts(project_root)],
         "plugin_uploads": len(iter_plugin_uploads(project_root)),
         "plugins": list_installed_plugins(project_root),
@@ -429,6 +438,8 @@ def validate_backup(zip_path: Path) -> Tuple[bool, str, Dict[str, Any]]:
                 detected.append("secrets")
             if _WIFI_REL.as_posix() in names:
                 detected.append("wifi")
+            if _YTM_REL.as_posix() in names:
+                detected.append("ytm_auth")
             if any(n.startswith(_FONTS_REL.as_posix() + "/") for n in names):
                 detected.append("fonts")
             if any(
@@ -481,8 +492,61 @@ def _extract_zip_safe(zip_path: Path, dest_dir: Path) -> None:
 
 
 def _copy_file(src: Path, dst: Path) -> None:
+    """Replace ``dst`` with ``src``, atomically, without needing to own ``dst``.
+
+    ``shutil.copy2`` opens the destination for writing, so it needs write
+    permission on the *existing file*. Several config files are installed
+    root-owned and group-readable while the web interface — which is what runs
+    a restore — deliberately runs as a non-root user. Restoring those failed
+    with EACCES even though the account could create files in the same
+    directory perfectly well.
+
+    Writing a temporary file alongside and renaming over the target needs only
+    directory permission, which the web user has. It is also atomic: a crash
+    mid-restore can no longer leave a half-written config behind.
+
+    The destination's existing mode is preserved when there is one, so
+    restoring secrets does not silently widen them to the umask default.
+    """
     dst.parent.mkdir(parents=True, exist_ok=True)
-    shutil.copy2(src, dst)
+
+    existing_mode: Optional[int] = None
+    existing_owner: Optional[Tuple[int, int]] = None
+    if dst.exists():
+        try:
+            info = dst.stat()
+            existing_mode = stat.S_IMODE(info.st_mode)
+            existing_owner = (info.st_uid, info.st_gid)
+        except OSError:
+            existing_mode = None
+            existing_owner = None
+
+    fd, tmp_name = tempfile.mkstemp(dir=str(dst.parent), prefix=f".{dst.name}.", suffix=".tmp")
+    os.close(fd)
+    tmp_path = Path(tmp_name)
+    try:
+        shutil.copyfile(src, tmp_path)
+        if existing_mode is not None:
+            os.chmod(tmp_path, existing_mode)
+        else:
+            shutil.copymode(src, tmp_path)
+        if existing_owner is not None:
+            # Replacing a file creates a new inode owned by whoever is running,
+            # which would silently move a root-owned config to the web user.
+            # Carry the previous owner across when the OS permits it — only
+            # root can hand a file to another user, so this is best-effort and
+            # a plain restore as the web user simply keeps its own ownership.
+            try:
+                os.chown(tmp_path, existing_owner[0], existing_owner[1])
+            except (OSError, PermissionError):
+                pass
+        os.replace(tmp_path, dst)
+    except BaseException:
+        try:
+            tmp_path.unlink()
+        except OSError:
+            pass
+        raise
 
 
 def restore_backup(
@@ -546,6 +610,18 @@ def restore_backup(
         elif (tmp_dir / _WIFI_REL).exists():
             result.skipped.append("wifi")
 
+        # YouTube Music session. Follows restore_wifi rather than getting its
+        # own flag: it is device-local auth in the same sense, and a separate
+        # toggle for one file would be noise in the restore dialog.
+        if options.restore_wifi and (tmp_dir / _YTM_REL).exists():
+            try:
+                _copy_file(tmp_dir / _YTM_REL, project_root / _YTM_REL)
+                result.restored.append("ytm_auth")
+            except OSError as e:
+                result.errors.append(f"Failed to restore ytm_auth.json: {e}")
+        elif (tmp_dir / _YTM_REL).exists():
+            result.skipped.append("ytm_auth")
+
         # User fonts — skip anything that collides with a bundled font.
         tmp_fonts = tmp_dir / _FONTS_REL
         if options.restore_fonts and tmp_fonts.exists():

src/plugin_system/store_manager.py

@@ -1143,7 +1143,7 @@ class PluginStoreManager:
         """
         registry = self.fetch_registry()
         plugins = registry.get('plugins', []) or []
-        plugin_info = next((p for p in plugins if p['id'] == plugin_id), None)
+        plugin_info = self._match_registry_entry(plugins, plugin_id)
 
         if not plugin_info:
             return None
@@ -1183,6 +1183,37 @@ class PluginStoreManager:
 
         return plugin_info
 
+    @staticmethod
+    def _match_registry_entry(plugins: List[Dict], plugin_id: str) -> Optional[Dict]:
+        """Find a registry entry by its id, or by the directory it installs to.
+
+        Four shipped plugins have a registry ``id`` that differs from the ``id``
+        in their own manifest: ``weather`` installs to ``plugins/ledmatrix-weather``,
+        and likewise stocks, music and leaderboard. Installation already prefers
+        the manifest id for the directory name, so on disk, in ``config.json``
+        and in a backup manifest those plugins are called ``ledmatrix-weather``.
+
+        Only the registry calls them ``weather``, and nothing resolved that in
+        reverse: restoring a backup asked the store for ``ledmatrix-weather``
+        and got "Plugin not found in registry", silently dropping four enabled
+        plugins from a restored device.
+
+        Matching ``plugin_path`` fixes it without renaming any published id,
+        which would orphan ``plugin_state.json`` entries keyed on the old ones.
+        Exact id always wins, so an entry whose *path* happens to collide with
+        another entry's id cannot shadow it.
+        """
+        if not plugin_id:
+            return None
+        exact = next((p for p in plugins if p.get('id') == plugin_id), None)
+        if exact is not None:
+            return exact
+        for entry in plugins:
+            path = (entry.get('plugin_path') or '').rstrip('/')
+            if path and path.rsplit('/', 1)[-1] == plugin_id:
+                return entry
+        return None
+
     def get_registry_info(self, plugin_id: str) -> Optional[Dict]:
         """
         Get plugin information from the registry cache only (no GitHub API calls).
@@ -1198,7 +1229,7 @@ class PluginStoreManager:
         """
         registry = self.fetch_registry()
         plugins = registry.get('plugins', []) or []
-        return next((p for p in plugins if p.get('id') == plugin_id), None)
+        return self._match_registry_entry(plugins, plugin_id)
     
     def install_plugin(self, plugin_id: str, branch: Optional[str] = None) -> bool:
         """Install a plugin, keeping any existing install until the new one is

test/test_backup_manager.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import stat
 import zipfile
 from pathlib import Path
 
@@ -41,6 +42,13 @@ def _make_project(root: Path) -> Path:
         json.dumps({"ap_mode": {"ssid": "LEDMatrix"}}),
         encoding="utf-8",
     )
+    # Device-local auth that lives in config/ like the three above. It was
+    # omitted from backups, so a restore silently signed the user out of
+    # YouTube Music and they had to re-authenticate by hand.
+    (root / "config" / "ytm_auth.json").write_text(
+        json.dumps({"token": "YTM-TOKEN"}),
+        encoding="utf-8",
+    )
 
     fonts = root / "assets" / "fonts"
     fonts.mkdir(parents=True)
@@ -240,6 +248,10 @@ def test_restore_roundtrip(project: Path, empty_project: Path, tmp_path: Path) -
     restored_secrets = json.loads((empty_project / "config" / "config_secrets.json").read_text())
     assert restored_secrets["ledmatrix-weather"]["api_key"] == "SECRET"
 
+    assert "ytm_auth" in result.restored
+    restored_ytm = json.loads((empty_project / "config" / "ytm_auth.json").read_text())
+    assert restored_ytm["token"] == "YTM-TOKEN"
+
     # User font restored, bundled font untouched.
     assert (empty_project / "assets" / "fonts" / "my-custom-font.ttf").read_bytes() == b"\x00\x01USER"
     assert (empty_project / "assets" / "fonts" / "5x7.bdf").read_text() == "BUNDLED"
@@ -282,3 +294,39 @@ def test_restore_rejects_malicious_zip(empty_project: Path, tmp_path: Path) -> N
     # validate_backup catches it before extraction.
     assert not result.success
     assert any("unsafe" in e.lower() for e in result.errors)
+
+
+def test_restore_over_a_file_the_user_cannot_write(
+    project: Path, empty_project: Path, tmp_path: Path
+) -> None:
+    """Restore must not need write permission on the destination *file*.
+
+    Reproduces what a fresh install leaves behind: config files owned by root
+    and only group-readable, while the web interface that performs the restore
+    runs as a non-root user. shutil.copy2 opens the destination for writing and
+    failed with EACCES; writing alongside and renaming needs only directory
+    permission, which that account has.
+
+    Simulated here by making the destination read-only — the owner cannot
+    open it for writing either, but can still replace it within its directory.
+    """
+    zip_path = create_backup(project, output_dir=tmp_path / "exports")
+
+    # Pre-existing, read-only destinations.
+    (empty_project / "config").mkdir(parents=True, exist_ok=True)
+    for name in ("config.json", "config_secrets.json", "wifi_config.json", "ytm_auth.json"):
+        target = empty_project / "config" / name
+        target.write_text("{}", encoding="utf-8")
+        target.chmod(0o444)
+
+    result = restore_backup(zip_path, empty_project, RestoreOptions())
+
+    assert result.success, result.errors
+    for section in ("config", "secrets", "wifi", "ytm_auth"):
+        assert section in result.restored, f"{section} not restored: {result.errors}"
+
+    restored = json.loads((empty_project / "config" / "config.json").read_text())
+    assert restored["my-plugin"]["favorites"] == ["A", "B"]
+
+    # The destination's mode is preserved rather than widened to the umask.
+    assert stat.S_IMODE((empty_project / "config" / "config_secrets.json").stat().st_mode) == 0o444

test/test_registry_id_resolution.py

@@ -0,0 +1,107 @@
+"""A plugin must be findable in the registry by the id it calls itself.
+
+Four shipped plugins have a registry ``id`` that differs from the ``id`` in
+their own ``manifest.json``:
+
+    directory / manifest.json id      registry id
+    ledmatrix-weather                 weather
+    ledmatrix-stocks                  stocks
+    ledmatrix-music                   music
+    ledmatrix-leaderboard             leaderboard
+
+The installer already knows about this: it deliberately names the install
+directory after the *manifest* id (store_manager, "Use manifest ID for
+directory name"), and warns when the two disagree. So on disk, in
+``config.json`` and in a backup manifest, these plugins are called
+``ledmatrix-weather``. Only the registry calls them ``weather``.
+
+Nothing resolved that in reverse. Asking the store to install
+``ledmatrix-weather`` -- which is exactly what restoring a backup does --
+failed with "Plugin not found in registry", and four enabled plugins went
+missing from a restored device with no error surfaced to the user.
+
+Renaming the registry ids would orphan existing ``plugin_state.json`` entries
+keyed on the old ones, so the lookup resolves ``plugin_path`` instead: the
+registry already records ``plugins/ledmatrix-weather``, which is unambiguous
+and needs no published identity to change.
+"""
+
+import os
+import sys
+from typing import Any, Dict, List, Optional
+
+import pytest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from src.plugin_system.store_manager import PluginStoreManager  # noqa: E402
+
+
+# Shaped like the real registry: id and plugin_path basename disagree for the
+# first entry, agree for the second.
+REGISTRY: Dict[str, List[Dict[str, Any]]] = {
+    "plugins": [
+        {
+            "id": "weather",
+            "name": "Weather",
+            "plugin_path": "plugins/ledmatrix-weather",
+            "repo": "https://github.com/ChuckBuilds/ledmatrix-plugins",
+        },
+        {
+            "id": "ledmatrix-flights",
+            "name": "Flights",
+            "plugin_path": "plugins/ledmatrix-flights",
+            "repo": "https://github.com/ChuckBuilds/ledmatrix-plugins",
+        },
+        {
+            "id": "third-party",
+            "name": "Third Party",
+            "plugin_path": "",
+            "repo": "https://github.com/someone/thing",
+        },
+    ]
+}
+
+
+@pytest.fixture
+def store(monkeypatch: pytest.MonkeyPatch) -> PluginStoreManager:
+    manager = PluginStoreManager.__new__(PluginStoreManager)
+    monkeypatch.setattr(manager, "fetch_registry", lambda *a, **k: REGISTRY, raising=False)
+    return manager
+
+
+def _ids(entry: Optional[Dict[str, Any]]) -> Optional[str]:
+    return entry.get("id") if entry else None
+
+
+class TestRegistryLookupByManifestId:
+    def test_exact_registry_id_still_resolves(self, store: PluginStoreManager) -> None:
+        assert _ids(store.get_registry_info("weather")) == "weather"
+
+    def test_manifest_id_resolves_via_plugin_path(self, store: PluginStoreManager) -> None:
+        """The case that broke restore: asked by the name on disk."""
+        assert _ids(store.get_registry_info("ledmatrix-weather")) == "weather", (
+            "a plugin installed as 'ledmatrix-weather' could not be found in a "
+            "registry that lists it under plugin_path plugins/ledmatrix-weather")
+
+    def test_matching_id_and_path_unaffected(self, store: PluginStoreManager) -> None:
+        assert _ids(store.get_registry_info("ledmatrix-flights")) == "ledmatrix-flights"
+
+    def test_unknown_plugin_still_returns_none(self, store: PluginStoreManager) -> None:
+        assert store.get_registry_info("no-such-plugin") is None
+
+    def test_empty_plugin_path_is_not_a_wildcard(self, store: PluginStoreManager) -> None:
+        """Third-party entries carry plugin_path "" — that must not match ""."""
+        assert store.get_registry_info("") is None
+
+    def test_exact_id_wins_over_a_path_match(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        """If some other entry's path collides with a real id, id wins."""
+        registry = {
+            "plugins": [
+                {"id": "decoy", "plugin_path": "plugins/weather"},
+                {"id": "weather", "plugin_path": "plugins/ledmatrix-weather"},
+            ]
+        }
+        manager = PluginStoreManager.__new__(PluginStoreManager)
+        monkeypatch.setattr(manager, "fetch_registry", lambda *a, **k: registry, raising=False)
+        assert _ids(manager.get_registry_info("weather")) == "weather"

web_interface/blueprints/api_v3.py

@@ -7848,7 +7848,31 @@ def clear_old_errors():
 # Backup / Restore
 # ---------------------------------------------------------------------------
 
-_BACKUP_EXPORT_DIR = PROJECT_ROOT / "config" / "backups" / "exports"
+def _resolve_backup_export_dir() -> Path:
+    """Where exported backups live: beside the install, not inside it.
+
+    They used to be written to ``<project>/config/backups/exports``. That is
+    inside the directory a reinstall deletes, so the documented recovery path
+    -- export a backup, then reinstall -- destroyed the backup it had just
+    told the user to make. Anyone who downloaded the ZIP was fine; anyone
+    relying on the on-device copy was not.
+
+    Falls back to the old location when the parent directory is not writable,
+    so an unusual layout degrades to previous behaviour instead of failing to
+    export at all.
+    """
+    preferred = PROJECT_ROOT.parent / "ledmatrix-backups"
+    try:
+        preferred.mkdir(parents=True, exist_ok=True)
+        probe = preferred / ".writetest"
+        probe.write_text("", encoding="utf-8")
+        probe.unlink()
+        return preferred
+    except OSError:
+        return PROJECT_ROOT / "config" / "backups" / "exports"
+
+
+_BACKUP_EXPORT_DIR = _resolve_backup_export_dir()
 
 
 def _safe_backup_path(filename: str) -> Path:
@@ -8002,7 +8026,22 @@ def backup_restore():
 
         data = result.to_dict()
         if not result.success:
-            return jsonify({'status': 'error', 'message': 'Restore had errors', 'data': data}), 500
+            # Name what failed, and what nonetheless landed. A restore is
+            # partial far more often than it is total -- a fresh install can
+            # leave config_secrets.json unwritable by the web service, so
+            # config restores and secrets do not. "Restore had errors" alone
+            # left the user unable to tell a wholly failed restore from one
+            # that quietly dropped their API keys.
+            failed_plugins = [p.get('plugin_id') for p in (result.plugins_failed or [])]
+            parts = []
+            if result.restored:
+                parts.append(f"restored: {', '.join(result.restored)}")
+            if result.errors:
+                parts.append(f"failed: {'; '.join(result.errors)}")
+            if failed_plugins:
+                parts.append(f"plugins not reinstalled: {', '.join(failed_plugins)}")
+            message = 'Restore incomplete — ' + ('. '.join(parts) if parts else 'see logs')
+            return jsonify({'status': 'error', 'message': message, 'data': data}), 500
         return jsonify({'status': 'success', 'data': data})
     except Exception as e:
         logger.error("backup_restore failed: %s", e, exc_info=True)