(sorry if this should not make any sense to you. This is a note for me to go back to. Even though I bring new machines online regurlarly I forget the exact steps for this)
on X
ssh-keygen -t dsa
add content of .ssh/id_dsa.pub in the end of .ssh/authorized_keys2 on Y. Only thing we need to do on Y.
after boot of X run
ssh_info_file=~/.ssh-agent-info-`hostname`
ssh-agent >$ssh_info_file
chmod 600 $ssh_info_file
source $ssh_info_file
ssh-add ~/.ssh/id_dsa
before login from X to Y
source /root/.ssh-agent-info-hostname