def create_backup(self):
        """Ask controller to create a backup archive file, response contains the path to the backup file.

        Warning: This process puts significant load on the controller may
                 render it partially unresponsive for other requests.
        """

        js = json.dumps({'cmd': 'backup'})
        params = urllib.urlencode({'json': js})
        answer = self._read(self.api_url + 'cmd/system', params)

        return answer[0].get('url')
Ask controller to create a backup archive file, response contains the path to the backup file.

        Warning: This process puts significant load on the controller may
                 render it partially unresponsive for other requests.