报错如下：
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@ 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 a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
SHA256:MCyWt2OxfujjNCtuvwiyftK2Ir3ri2wVWtiQM4dZYT9j8.
Please contact your system administrator.
Add correct host key in /home/aa/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /home/aa/.ssh/known_hosts:7742
Password authentication is disabled to avoid man-in-the-middle attacks.
Keyboard-interactive authentication is disabled to avoid man-in-the-middle attacks.
Welcome to Ubuntu 18.04.6 LTS (GNU/Linux 4.15.0-202-generic x86_64)解决办法：
根据提示，删掉/home/aa/.ssh/known_hosts 里相应的ip