remove key from known_hosts

For when you get that oh so annoying

The RSA host key for foo-bar.net has changed, and the key for the corresponding IP address 127.0.0.1 is unchanged. This could either mean that DNS SPOOFING is happening or the IP address for the host and its host key have changed at the same time. Offending key for IP in homeuser.sshknown_hosts:6

Run the following command where in the above example hostname would be foo-bar.net.

ssh-keygen -R hostname