Log in SSH server with Passwordless mode.

[On the client side:]

1)

#ssh-keygen -t rsa

Keep pressing [ENTER] button until the end.

2)

#ssh-copy-id -i $HOME/.ssh/id_rsa.pub root@192.168.0.3:

The IP address shown above, namely 192.168.0.3, refers to the server's IP address.

3)

#ssh root@192.168.0.3 "chmod 700 .ssh; chmod 640 .ssh/authorized_keys"

Done!