感谢大佬：https://blog.csdn.net/wd2014610/article/details/79945424
一、今天在使用SSH，连接远程服务器的时候，刚开始是没问题的。
后来阿里云主机重装了一下系统后，再也连不上了。一直报一个错。
~ ⌚ 22:49:52
$ ssh root@47.98.233.15
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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
SHA256:8hgJ8jpcBr1tm6HS72FpXwMrjba8MQqlqYJQLPB/Qf4.
Please contact your system administrator.
Add correct host key in /Users/wangdong/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /Users/wangdong/.ssh/known_hosts:26
ECDSA host key for 47.98.233.15 has changed and you have requested strict checking.
Host key verification failed.
二、解决方法，看错误日志中有一句
Add correct host key in /Users/wangdong/.ssh/known_hosts to get rid of this message.
三、以编辑器的方式进入这个文件
vi /Users/wangdong/.ssh/known_hosts
四、将红线框部分删除掉
五、再次进行远程连接
~ ⌚ 22:52:18
$ ssh root@47.98.233.15
The authenticity of host '47.98.233.15 (47.98.233.15)' can't be established.
ECDSA key fingerprint is SHA256:8hgJ8jpcBr1tm6HS72FpXwMrjba8MQqlqYJQLPB/Qf4.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '47.98.233.15' (ECDSA) to the list of known hosts.
root@47.98.233.15's password:
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-105-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
Welcome to Alibaba Cloud Elastic Compute Service !
root@iZbp17cj14ulhfrlj02rkaZ:~#
问题就解决了，原因是因为才重装系统后，再次进行远程连接上，在输入yes后，本机会将远程机器的信息，写到/Users/wangdong/.ssh/known_hosts文件中，所以如果远程重装系统了，本机一定要先清理掉。