ssh remote host identification has changed

Question

I\'ve reinstalled my server and I am getting these messages:

[user@hostname ~]$ ssh root@pong
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@           


        

Answer 1

The problem is that you've previously accepted an SSH connection to a remote computer and that remote computer's digital fingerprint or SHA256 hash key has changed since you last connected. Thus when you try to SSH again or use github to pull code, which also uses SSH, you get an error. Why? Because you're using the same remote computer address as before but the remote computer is responding with a different fingerprint. Therefore, it's possible that someone is spoofing the computer you previously connected to. This is a security issue.

If you're 100% sure that the remote computer isn't compromised, hacked, being spoofed, etc then all you need to do is delete the entry in your known_hosts file for the remote computer. That will solve the issue as there will no longer be a mismatch with SHA256 fingerprint IDs when connecting.

On Mac here's what I did:

1) Find the line of output that reads RSA host key for servername:port has changed and you have requested strict checking. You'll need both the servername and potentially port from that log output.

2) Back up the SSH known hosts file cp /Users/yourmacusername/.ssh/known_hosts /Users/yourmacusername/.ssh/known_hosts.bak

3) Find the line where the computer's old fingerprint is stored and delete it. You can search for the specific offending remote computer fingerprint using the servername and port from step #1. nano /Users/yourmacusername/.ssh/known_hosts

4) CTRL-X to quit and choose Y to save changes

Now type ssh -p port servername and you will receive the original prompt you did when you first tried to SSH to that computer. You will then be given the option to save that remote computer's updated SHA256 fingerprint to your known_hosts file. If you're using SSH over port 22 then the -p argument is not necessary.

Any issues you can restore the original known_hosts file: cp /Users/yourmacusername/.ssh/known_hosts.bak /Users/yourmacusername/.ssh/known_hosts