Avoiding duplicate entries in ~/.ssh/known_hosts

Question

I have my DNS search path set to ".intranet", ie, /etc/resolv.conf contains:

search intranet

When I SSH to a host using a FQDN, like "mailserver.intranet", it adds an entry for "mailserver.intranet" to ~/.ssh/known_hosts. If I later SSH to this same host but using the simple "mailserver" name, SSH adds another entry to known_hosts for "mailserver".

Is it possible to make SSH always use FQDN in known_hosts to avoid this duplicity?

Answer 1

You could use aliases for host keys:

Host <hostname>*
    hostname    <fqdn>
    HostKeyAlias    <alias>

Your key will be saved to known_hosts as "alias" instead of "hostname" either short or long, the downside is you have to write an entry for each one of your hosts.

Please note the '*' after the hostname at the first line, it's needed for matching both the short and long hostname.