permissions

backup.sh

@@ -96,6 +96,9 @@ check_mount
 # Fail early if the backup base directory doesn't exist (drive not mounted / path wrong)
 [ -d "$BACKUP_BASE" ] || die "Backup base directory $BACKUP_BASE does not exist."
 
+# Must be able to write into the backup base (e.g. run as root via sudo/cron)
+[ -w "$BACKUP_BASE" ] || die "No write permission on $BACKUP_BASE — run as root (sudo)."
+
 # Locking — base dir is confirmed to exist, so the lockfile write will succeed
 lockfile="${BACKUP_BASE}/.backup.lock"
 cleanup() { rm -f "$lockfile"; }