Server Machine 1) in server, in /etc/ssh/sshd_config, set
HostbasedAuthentication yes IgnoreUserKnownHosts yes
and restart sshd
2) put client's machine name to /etc/ssh/shosts.equiv (assume the client is posic021)
3) put the client machine's host key to /etc/ssh/ssh_known_hosts, add the client machine's name/full domain name/ip before that, e.g
posic021,posic021.domain.name,141.142.xxx.xxx, ssh-rsa .....
4) For HostBasedAuthentication to work with root, In the server machine,
you need have the file /root/.shosts
You also need to set
in /etc/ssh/sshd_config and then restart sshd.