[root@controller ~]# ssh username@xxx.xxx.xxx.xxx
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
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 a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
b3:1f:65:0f:52:f0:23:5d:93:44:79:6a:d8:2f:bb:46.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending RSA key in /root/.ssh/known_hosts:6
RSA host key for xxx.xxx.xxx.xxx has changed and you have requested strict checking.
Host key verification failed.
[root@controller ~]# vi .ssh/known_hosts

若遇此情况 请注意

Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending RSA key in /root/.ssh/known_hosts:6

将正确的RSAkey添加进去，或者删除原有的即可