One-liner to remove an incorrect entry in the SSH known_hosts file

When a SSH-key changed, this warning is displayed:

ssh -l username 172.16.12.34

Warning:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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 ECDSA key sent by the remote host is
aa:bb:cc:a2:b6:87:bd:43:f9:ff:<wbr />02:8e:a6:b8:29:42.
Please contact your system administrator.
Add correct host key in /home/remi/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /home/remi/.ssh/known_hosts:6

In case you know the host identification has changed, you can safely discard this warning.

You could run ‘vim ~/.ssh/known_hosts‘ enter ‘6G‘ to go to the 6th line, ‘dd‘ to delete that line and finally ‘:wq‘ to save the file. But, wouldn’t a one-liner be handy?

Try:

ssh-keygen -R 172.24.111.132

Output:

/home/remi/.ssh/known_hosts updated.
Original contents retained as /home/remi/.ssh/known_hosts.

I’ve tested this on Ubuntu, Debian, SUSE and Red Hat Enterprise Linux.

In case you get this error:

fopen: No such file or directory

There isn’t a ‘known_hosts’ file in ‘~/.ssh/’. You can use the -f flag to specify the right file.