Remove key from known_hosts

I built several virtual machines during the last few weeks. The problem is, the .ssh/known_hosts gives me the Man in the middle warning. This happens because another fingerprint is associated with the virtual machine IP.

In the .ssh/known_hosts file, however, I don't find the record related to the IP, only two bizarre, key-like strings and "ssh-rsa".

Does anyone have any ideas about how to remove the old key from known_hosts?

sed -i '6d' ~/.ssh/known_hosts

Will modify the file ~/.ssh/known_hosts:6 , removing the 6th line.

In my opinion, using ssh-keygen -R is a better solution for an openssh power user, while your regular Linux admin would do better to keep his/her sed skills fresh by using the above method.

The simplest solution is:

rm -f .ssh/known_hosts

ssh will recreate the file again, but you lose key checking for other hosts!

Or, you can use:

ssh-keygen -R "hostname"

Or the ssh "man-in-the-middle" message should indicate which line of the known_hosts file has the offending fingerprint. Edit the file, jump to that line and delete it.

There is an ssh-keygen switch (-R) for this.

man ssh-keygen reads:

-R hostname

Removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed hosts (see the -H option above).

You need to run the following command to get rid of this problem. Open the terminal and type the following command:

For all examples below just replace the value after -R:

ssh-keygen -R server-name
ssh-keygen -R server.ip.addre.ss
ssh-keygen -R 202.54.1.5
ssh-keygen -R server1.example.com