Setting up passwordless SSH logins on ubuntu

First setup a clean install of ssh and config it from local and remote

sudo apt-get install openssh-server
 ssh -l username ipaddresss
 ifconfig | grep "inet addr"

sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.factory-defaults
 sudo chmod a-w /etc/ssh/sshd_config.factory-defaults
 sudo vi /etc/ssh/sshd_config

Then add(or change) the lines too read the following (to diable password loging and forwarding and spec limited access)

PasswordAuthentication no
 AllowTcpForwarding no
 X11Forwarding no
 AllowUsers yourRemoteUsername

Then add your key (do it now before restart or you will need a console access)

cat >> .ssh/authorized_keys 

paste in the one line with the rsa public key info and then reboot the machine or restart ssh with.

sudo /etc/init.d/ssh restart

Refer:
https://help.ubuntu.com/community/SSH/OpenSSH/Configuring#disable-password-authentication
https://help.ubuntu.com/community/SSH/OpenSSH/Keys