feat(build): standardize in-container update backup recovery

Auto-restore on update failure via create_backup ERR trap and clear backup stores after successful updates inside the LXC start() flow.

Co-authored-by: Cursor <cursoragent@cursor.com>

misc/build.func

@@ -3692,6 +3692,28 @@ runtime_script_status_guard() {
   return 0
 }
 
+# ------------------------------------------------------------------------------
+# _run_update_script()
+#
+# - Runs update_script inside the LXC with standardized backup recovery
+# - create_backup() arms an ERR trap; successful updates clear the backup store
+# - Works even when update_script ends with exit (EXIT trap)
+# ------------------------------------------------------------------------------
+_run_update_script() {
+  local _update_rc=0
+  _on_update_script_exit() {
+    local _exit_rc=$?
+    trap - EXIT
+    if [[ $_exit_rc -eq 0 ]] && declare -f clear_update_backup &>/dev/null; then
+      clear_update_backup
+    fi
+    exit "$_exit_rc"
+  }
+  trap '_on_update_script_exit' EXIT
+  update_script || _update_rc=$?
+  return "$_update_rc"
+}
+
 # ------------------------------------------------------------------------------
 # start()
 #
@@ -3713,7 +3735,7 @@ start() {
     ensure_profile_loaded
     get_lxc_ip
     runtime_script_status_guard || return 0
-    update_script
+    _run_update_script
     run_addon_updates
     update_motd_ip
     cleanup_lxc
@@ -3724,7 +3746,7 @@ start() {
     ensure_profile_loaded
     get_lxc_ip
     runtime_script_status_guard || return 0
-    update_script
+    _run_update_script
     run_addon_updates
     update_motd_ip
     cleanup_lxc
@@ -3754,7 +3776,7 @@ start() {
     ensure_profile_loaded
     get_lxc_ip
     runtime_script_status_guard || return 0
-    update_script
+    _run_update_script
     run_addon_updates
     update_motd_ip
     cleanup_lxc

misc/tools.func

@@ -1162,6 +1162,7 @@ create_backup() {
 
   if [[ -f "$manifest" ]]; then
     msg_ok "Existing backup found at ${store}, skipping backup"
+    trap '_restore_update_backup_on_error' ERR
     return 0
   fi
 
@@ -1186,6 +1187,24 @@ create_backup() {
     echo "$path" >>"$manifest"
   done
   msg_ok "Backed up data to ${store}"
+  trap '_restore_update_backup_on_error' ERR
+}
+
+_restore_update_backup_on_error() {
+  local _err=$?
+  trap - ERR
+  if [[ -f "${BACKUP_DIR:-/opt/${NSAPP:-app}.backup}/.manifest" ]]; then
+    msg_error "Update failed (exit ${_err}) – restoring backup"
+    restore_backup
+  fi
+  exit "${_err:-1}"
+}
+
+clear_update_backup() {
+  local store="${BACKUP_DIR:-/opt/${NSAPP:-app}.backup}"
+  [[ -d "$store" ]] || return 0
+  rm -rf "$store"
+  trap - ERR
 }
 
 restore_backup() {
@@ -1208,6 +1227,7 @@ restore_backup() {
     cp -a "$src" "$path"
   done <"$manifest"
   rm -rf "$store"
+  trap - ERR
   msg_ok "Restored data"
 }
 

tools/ci/check-update-backup.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+# Copyright (c) 2021-2026 community-scripts ORG
+# License: MIT
+#
+# Flags ct/*.sh update_script blocks that mutate config/data destructively
+# without calling create_backup. Used in CI / local review before merge.
+
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+CT_DIR="${ROOT}/ct"
+FAIL=0
+CHECKED=0
+FLAGGED=0
+
+check_file() {
+  local file="$1"
+  local base content block
+  base="$(basename "$file")"
+  content="$(<"$file")"
+  [[ "$content" == *"function update_script"* ]] || return 0
+  CHECKED=$((CHECKED + 1))
+
+  block="$(python3 - "$file" <<'PY'
+import re, sys
+text = open(sys.argv[1]).read()
+m = re.search(r'function update_script\(\).*?(?=^function |\Z)', text, re.S | re.M)
+print(m.group() if m else "")
+PY
+)"
+
+  [[ -n "$block" ]] || return 0
+  [[ "$block" == *"create_backup"* ]] && return 0
+
+  if echo "$block" | grep -qE 'sed -i|\.env|settings\.(py|json)|config\.(json|yml|yaml)|/etc/[^ ]+\.(conf|env)'; then
+    if echo "$block" | grep -qE 'rm -rf|find .* -delete|mv .*\.(bak|old)'; then
+      echo "MISSING create_backup: ct/${base}"
+      FLAGGED=$((FLAGGED + 1))
+      FAIL=1
+    fi
+  fi
+}
+
+for f in "$CT_DIR"/*.sh; do
+  [[ -f "$f" ]] || continue
+  check_file "$f"
+done
+
+echo "Checked ${CHECKED} update scripts, flagged ${FLAGGED} without create_backup"
+exit "$FAIL"