Add Public SSH Key to Remote Server in a Single Command

From HowToGeek

If you want to setup SSH keys to allow logging in without a password, you can do so with a single command.

The first thing you'll need to do is make sure you've run the keygen command to generate the keys:

ssh-keygen -t rsa

Then use this command to push the key to the remote server, modifying it to match your server name.

cat ~/.ssh/id_rsa.pub | ssh user@hostname 'cat >> .ssh/authorized_keys'