def uuid2dn(self, backend, uuid, from_db_only=False):
        dn = ObjectBackendRegistry.backends[backend].uuid2dn(uuid)
        if dn is None and from_db_only is True:
            # fallback to db
            if self.__index is None:
                self.__index = PluginRegistry.getInstance("ObjectIndex")
            res = self.__index.search({'uuid': uuid}, {'dn': 1})
            if len(res) == 1:
                dn = res[0]['dn']
        return dn