When I try to connect Linux server via SSH. ” WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! ” message shows and reject me from connecting SSH. 
This problem occurred by linux clients store certificate key in “known_hosts” storage when the first connection. If you reset or renew this server, SSH certificate key will be changed. However, Linux clients discovered the remote server certificate key was not fit with the certificate stored in “known_hosts” storage, your connection will be refused.
To fix this problem, just use the following command to delete “known_hosts” of a unique server.
ssh-keygen -R serverip(change to ssh server ip)
Type YES to continue
Are you sure you want to continue connecting (yes/no)?
That All~
After the process was done. You can connect your server via SSH without any error message.
REF: https://blog.allenchou.cc/warning-remote-host-identification-has-changed/
ERROR MESSAGE:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ 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 Please contact your system administrator. Add correct host key in /home/conbar/.ssh/known_hosts to get rid of this message. Offending key in /home/conbar/.ssh/known_hosts:10 RSA host key for strict checking. Host key verification failed.