1. cd /home/user/.ssh
2. Using ssh-keygen create a rsa and public key
$ ssh-keygen -t rsa
The private key will save as .ssh/id_rsa.
The public key will save as .ssh/id_rsa.pub.
3. Copy the .ssh/id_rsa.pub in file .ssh/authorized_keys of the system you wish to SSH to without being prompted for a password.
$ scp id_rsa.pub email@example.com:/home/user1/.ssh
4. Add the key to the .ssh/authorized_keys.
5. Now you can login to the system without password.