配置热流复制时postgresql 9.0归档出错

当我尝试在postgresql上执行归档命令时,我收到警告,要求我无休止地等待.我按以下顺序执行命令：

SELECT pg_start_backup('base_backup');

cd /var/lib/postgresql/9.0/
sudo tar -cjf ~/postgres-data.tar.bz2 main

SELECT pg_stop_backup();

为此,我得到以下输出：

NOTICE:  pg_stop_backup cleanup done,waiting for required WAL segments to be archived
WARNING:  pg_stop_backup still waiting for all required WAL segments to be archived (60 seconds elapsed)
HINT:  Check that your archive_command is executing properly.  pg_stop_backup can be cancelled safely,but the database backup will not be usable without all the WAL segments.
WARNING:  pg_stop_backup still waiting for all required WAL segments to be archived (120 seconds elapsed)
HINT:  Check that your archive_command is executing properly.  pg_stop_backup can be cancelled safely,but the database backup will not be usable without all the WAL segments.

这继续保持下去,警告永远不会结束.如果有人遇到这个问题,请告诉我.