How to fix the git warning "ECDSA host key for 'github.com' differs from the key for the IP address '140.82.113.3'"

If GitHub's recent RSA SSH host key update causes your system to throw this error:

Warning: the ECDSA host key for 'github.com' differs from the key for the IP address '140.82.113.3'

The solution is a quick fix. The next lines of the error will read something like this:

Offending key for IP in ~/.ssh/known_hosts:X
Matching host key in ~/.ssh/known_hosts:Y
Are you sure you want to continue connecting (yes/no)?

Where X is the line number containing the IP address we want to remove. So...

Run the following command:

vi ~/.ssh/known_hosts

And ⬇️ to line X and run the following to delete the line and exit vi:

dd
:x

Voila!

Comments

[Dan Mercer]

You can also do sed -e "Xd" ~/.ssh/known_hosts to delete line X (the line number from above). A little bit easier than using Vim. 😅

[xtofl]

Would you need the in-place argument? sed -i "Xd" ~/.ssh/known_hosts?

[xtofl]

While this does the trick, it bypasses the tools that are offered by the ssh package.

The ssh package has a tool called ssh-keygen with a 'remove' subcommand -R.

So you should be using ssh-keygen -R 140.82.113.3.

Warning: the ECDSA host key for 'github.com' differs from
the key for the IP address '140.82.121.3'
Offending key for IP in /home/xtofl/.ssh/known_hosts:12
Matching host key in /home/xtofl/ssh/known_hosts:58
Are you sure you want to continue connecting (yes/no)?
^C


09:28 $ ssh-keygen -R 140.82.121.3
# Host 140.82.121.3 found: line 12
/home/xtofl/.ssh/known_hosts updated.
Original contents retained as /home/xtofl/.ssh/known_hosts.old