ssh keys for pi

https://www.raspberrypi.org/documentation/remote-access/ssh/passwordless.md

http://www.aupcgroup.com/blog/index.php?/archives/4-Securing-Raspbian.html

ssh-keygen -t rsa -C pi@raspberrypi -f ~/.ssh/raspberrypi

cat ~/.ssh/raspberrypi.pub | ssh pi@raspberrypi 'cat >> .ssh/authorized_keys'