Please let me add something concrete here. In "common/applicationinstance.py" beginning with line 53 "ApplicationInstance.check()" def check(self, autoExit = False): """ Check if the current application is already running ... Returns: bool: ``True`` if this is the only application instance """ #check if the pidfile exists if not os.path.isfile(self.pidFile): return True The "if" here confuses me. When the pidfile do NOT exists the "application" is running and is the "only instance"? Shouldn't it be the opposite? When the pidfile isthere (and has the process own PID as content) then the application is running and True should be returned. I don't think I've found a bug here. I assume I totally misunderstand something about the usage of pidfiles. Kind Christian