I find this really useful, just a call out to sed so I don't have to remember the syntax.
ssh_delete_key() {
sed -i -e ${1}d ~/.ssh/known_hosts
}
alias sshdel=ssh_delete_key
Usage:
[thomas@laptop: ~] $ ssh 192.168.0.1
OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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 RSA key sent by the remote host is
b7:da:35:ad:65:1c:5b:09:cf:a5:b3:e6:e7:0e:cf:43.
Please contact your system administrator.
Add correct host key in /home/thomas/.ssh/known_hosts to get rid of this message.
Offending RSA key in /home/thomas/.ssh/known_hosts:426
RSA host key for 192.168.0.1 has changed and you have requested strict checking.
Host key verification failed.
[thomas@laptop: ~] $ sshdel 426
[thomas@laptop: ~] $ ssh 192.168.0.1
The authenticity of host '167.143.72.26 (167.143.72.26)' can't be established.
RSA key fingerprint is b7:da:35:ad:65:1c:5b:09:cf:a5:b3:e6:e7:0e:cf:43.
Are you sure you want to continue connecting (yes/no)?