ssh登录，Host key verification failed的几种处理方法

- 修订历史History:
  2011.05.22   初稿

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- 系统： Ubuntu 10.04LTS 
- 软件： SSH

使用SSH登录某台机器，有时因为server端的一些变动，会出现以下信息：

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    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
50:e6:cb:58:bc:b7:a3:f6:e8:8f:46:a7:c1:5f:c2:df.
Please contact your system administrator.
Add correct host key in /home/cobyeah/.ssh/known_hosts to get rid of this message.
Offending key in /home/cobyeah/.ssh/known_hosts:7
RSA host key for 192.168.0.4 has changed and you have requested strict checking.
Host key verification failed.

（此处先不提及原理，只讲处理方法，需要了解原因的请留言或找其他资料）

这时候的处理方法，有3种：
1. 删除提示信息中，对应的行数，例如上例，需要删除/home/cobyeah/.ssh/known_hosts文件的第7行。

2. 删除整份/home/cobyeah/.ssh/known_hosts文件。

3. 修改/etc/ssh/ssh_config文件的配置，以后则不会再出现此问题

StrictHostKeyChecking no
UserKnownHostsFile /dev/null

参考：
http://www.symantec.com/connect/articles/ssh-host-key-protection
http://www.51testing.com/?uid-225738-action-viewspace-itemid-234384