已经运行过ssh-agent bash和通过ssh-add添加了秘钥，直接执行没有问题，但放置到定时任务中就会包下面的错误。
Permission denied (publickey).
rsync: connection unexpectedly closed (0 bytes received so far) [receiver]
rsync error: unexplained error (code 255) at io.c(600) [receiver=3.0.6]
下面是定时任务的脚本(要备份的IP这里用xxx代替)
#!/bin/bash
rsync -e "/usr/bin/ssh -p 22" -avpgolru --delete root@xxx.xxx.xxx.xxx:/data/mongodb/data/db/ /data/mongo/
