ssh远程登录出现：RSA host key for *.*.*.* has changed的解决办法

在做一个数据拷贝，要用到ssh，连接时提示：
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@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
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IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
bf:52:0b:5a:98:ce:b0:f6:d8:a8:eb:71:3c:b7:4c:9e.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending key in /root/.ssh/known_hosts:8
RSA host key for X.X.X.X has changed and you have requested strict checking.
Host key verification failed.

问题环境描叙：这里我用a和b描叙两台机器。a以前从b通过scp拷贝数据文件，并且已经做了免密码登录认证的，后来b机器出现问题，另外换了一台机器来替代b，但是保留了b原来的ip，然后继续从a机器ssh登录b时，提示上述问题。
解决办法：ssh-keygen -R bHostIp
或者直接删除a的~/.ssh/know_host文件，但是会丢失保存的其他主机的信息。