如何清除linux 缓存??

我菜我怕谁

我用putty远程登陆一台开ssh服务的linux机器.联结时候出现如下:

the server's host key is not cached in the registry . you have no guarantee that the server is the computer you think it is.
the server's rsa2 key fingerprint is : ssh-rsa 1024 34:43:45:d4:.....
if you trust this host, hit yes to add the key to pietty's cache and carry on connecting . if you want to carry on connecting just once ,without adding the key to the cache , hit No . if you do not trust this host , hit cancel to abandon the connection.

请问如果我选择" YES"　，那么我怎么才能　清除linux 上的缓存，让我的机器每次登陆这台linux 都出现这个提示？？？
高手帮忙！！！谢谢！！！