今天通過ssh和域名連接主機：
IcarusdeMacBook-Pro:~ icarus$ ssh root@icarusyu.me
出現了如下錯誤：
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: POSSIBLE DNS SPOOFING DETECTED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ The ECDSA host key for icarusyu.me has changed, and the key for the corresponding IP address 165.227.52.49 is unchanged. This could either mean that DNS SPOOFING is happening or the IP address for the host and its host key have changed at the same time. Offending key for IP in /Users/icarus/.ssh/known_hosts:4 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ 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 a host key has just been changed. The fingerprint for the ECDSA key sent by the remote host is SHA256:dcs240xWGNTvHg1qUkrkg4Pzb1pYzCgzghTHlEG+uZ0. Please contact your system administrator. Add correct host key in /Users/icarus/.ssh/known_hosts to get rid of this message. Offending ECDSA key in /Users/icarus/.ssh/known_hosts:3 ECDSA host key for icarusyu.me has changed and you have requested strict checking. Host key verification failed.
提示中出現了關鍵信息：
Add correct host key in /Users/icarus/.ssh/known_hosts to get rid of this message. Offending ECDSA key in /Users/icarus/.ssh/known_hosts:3
原因是在主機子系統每次成功ssh連接遠程操作，都會把你每個你訪問過計算機的公鑰(public key)都記錄在主機的目錄/Users/icarus/.ssh/known_hosts下，當下次訪問相同子機服務器時，會核對公鑰。如果公鑰不同，會發出警告，避免你受到DNS Hijack之類的攻擊。
解決辦法：
進入目錄刪除文件即可，然后重新連接就能發現連接上了。
IcarusdeMacBook-Pro:~ icarus$ cd ~/.ssh/
IcarusdeMacBook-Pro:.ssh icarus$ ls
known_hosts known_hosts.old
IcarusdeMacBook-Pro:.ssh icarus$ rm known_hosts
IcarusdeMacBook-Pro:.ssh icarus$ ssh root@icarusyu.me
The authenticity of host 'icarusyu.me (165.227.52.49)' can't be established.
ECDSA key fingerprint is SHA256:dcs240xWGNTvHg1qUkrkg4Pzb1pYzCgzghTHlEG+uZ0.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'icarusyu.me,165.227.52.49' (ECDSA) to the list of known hosts.
root@icarusyu.me's password:
Welcome to Ubuntu 16.04.4 LTS (GNU/Linux 4.4.0-116-generic x86_64)
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