How to edit known_hosts when several hosts share the same IP and DNS name?
As @Izzy suggested in an above comment, ssh tells you the offending line, and by removing that line, (saving it elsewhere), accepting the new key, and then copying the removed line back, you wind up with two keys for the same host, and ssh will accept either.
(You can also use ssh-keygen -H -F <hostname>
to find lines in your known_hosts file that match that hostname. Running this after copying the removed line back should list two entries.)
If anyone knows how to get PuTTY to do the same thing, I'd be very interested to hear about it.
The most straightforward solution here is just to use the same host keys for Linux and OS X. That is, pick one set of /etc/ssh/ssh_host_*_key*
files and copy them over to the other OS. Then the same host key will presented to an SSH client regardless of which OS you've booted into, and the SSH client will be none the wiser.
I found this that may help you with what you want to achieve.
Source: https://stackoverflow.com/questions/733753/how-to-handle-ssh-host-key-verification-with-2-different-hosts-on-the-same-but
Create a config file in your .ssh directory as follows:
Host server1 Hostname x1.example.com HostKeyAlias server1 CheckHostIP no Port 22001 User karl Host server2 Hostname x2.example.com HostKeyAlias server2 CheckHostIP no Port 22002 User karl
Explanation Below (from man ssh_config)
CheckHostIP
If this flag is set to "yes", ssh(1) will additionally check the host IP address in the known_hosts file. This allows ssh to detect if a host key changed due to DNS spoofing. If the option is set to "no", the check will not be executed. The default is "yes".
HostKeyAlias
Specifies an alias that should be used instead of the real host name when looking up or saving the host key in the host key database files. This option is useful for tunneling SSH connections or for multiple servers running on a single host.
The Username and Port line avoids you having to give those options on the command line, too, so you can just use:
% ssh server1 % ssh server2