问题：使用阿里云服务器，重置了一次系统，结果发现使用远程ssh无法连接，并且报了下边的错：
@ 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 33:78:e5:9a:e8:c5:47:73:81:a3:9b:4c:b0:ed:af:2d. 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:2 Password authentication is disabled to avoid man-in-the-middle attacks. Keyboard-interactive authentication is disabled to avoid man-in-the-middle attacks. Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).原因：出现这个问题的原因，是我重置了系统，服务器主体变了，原先连接生成的认证不能使用了，所以需要将原先的认证删除。
解决方案：
ssh-keygen -R [你要连接的IP]之后进行连接即可连接成功：
