public function runlevelToString($runlevel)
    {

        // flip the array with the string => integer runlevel definitions
        $runlevels = array_flip(Runlevels::singleton()->getRunlevels());
        if (isset($runlevels[$runlevel])) {
            return $runlevels[$runlevel];
        }

        // throw an exception if the runlevel is unknown
        throw new \Exception(sprintf('Request invalid runlevel to string conversion for %s', $runlevel));
    }