Take a snapshot of the system.

def request_snapshot(self, mode, priority=19, **kwargs):
        '''
        Take a snapshot of the system.
        '''
        if mode not in self.MODE:
            raise InspectorSnapshotException("Unknown mode: '{0}'".format(mode))

        if is_alive(self.pidfile):
            raise CommandExecutionError('Inspection already in progress.')

        self._prepare_full_scan(**kwargs)

        os.system("nice -{0} python {1} {2} {3} {4} & > /dev/null".format(
            priority, __file__, os.path.dirname(self.pidfile), os.path.dirname(self.dbfile), mode))