private function prepareClusteredMode()
    {
        $param_server = nbCLICheckOption('s', 'server', ':', false);
        if (strlen($param_server) === 0) {
            echo "Missed --server or -s option.\n";
            echo "Please revise your options and try again.\n";
        } else {
            $this->mode = CNabuEngine::ENGINE_MODE_CLUSTERED;
            $this->server_key = $param_server;
        }
    }