linux的ssh连接提示IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY

[root@localhost ~]# ssh root@172.16.2.220

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@                                                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 the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
7a:b5:cf:b6:af:6d:28:28:8f:c6:67:fe:19:6c:21:9d.
Please contact your system administrator.
Add correct host key in /home/ root /.ssh/known_hosts to get rid of this message.
Offending key in /home/ root /.ssh/known_hosts:7
RSA host key for 172.16.2.220 has changed and you have requested strict checking.
Host key verification failed.

解决方法：
[root@localhost ~]# rm ~/.ssh/known_hosts
ssh正常使用：
[root@localhost ~]# ssh root@172.16.2.220