Comment 1 for bug 267802

> This requires files in ~/.ssh for the nagios user

Not exactly. You can (and should) run ssh with the -F option to specify a configfile that will point to files in other locations. Example :

ssh -F /var/lib/nagios/ssh_config ...

/etc/nagios/ssh_config:
UserKnownHostsFile /var/lib/nagios/known_hosts
IdentityFile /var/lib/nagios/id_rsa
...

nagios shouldn't have a "real" home folder.

Closing as invalid, feel free to reopen if the provided solution is not working.