Client端以SSH連線到主機時，會要求產生認證資訊，儲存在client端的~/.ssh/known_ssh檔中。

如果有連線到多台不同主機，known_hosts裡面就會記錄許多記錄。

但是，假如server被重灌了，這樣子新的server就和known_hosts裡的狀態不同，
再連線時，就會出現底下錯誤：

[root@desktop10 ~]# ssh -X 192.168.0.110
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    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
0a:3e:d1:fb:de:3a:4f:eb:20:b7:44:50:76:61:36:46.
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:4
RSA host key for 192.168.0.110 has changed and you have requested strict checking.
Host key verification failed.

這時，最簡單的方式，就是將known_hosts這個檔刪除，往後再連線主機時，就再重新產生認證資訊就好了。

進入

vi /root/.ssh/known_host (將192.168.0.110這個連線的KEY給刪除就可以了)

或者

rm -rf /root/.ssh/known_host (直接將整個檔案給刪掉是最快的！！！)