SSH without password

Server1 root login to Server 2 root without password
[root@Server1]# ssh-keygen -t dsa -f /root/.ssh/id_dsa -N ""
(NO parapharse)
[root@Server1]# ssh-copy-id -i ~/.ssh/id_dsa.pub Server2

Server2 root login to Server1 root without password
[root@Server2# ssh-keygen -t dsa -f /root/.ssh/id_dsa -N ""
(NO parapharse)
[root@Server2]# ssh-copy-id -i ~/.ssh/id_dsa.pub Server1

Permanently add the key without prompting SSH
ssh -o StrictHostKeyChecking=no root@Server1