SSH

SSH is a network protocoll to securely connect to a computer.

Enable root login via SSH

Edit the /etc/ssh/sshd_config and change the line containing PermitRootLogin
to PermitRootLogin yes.

Add login via SSH public key

To enable easy login without password you can add the contents of the file
~/.ssh/id_rsa.pub from your local machine to the file ~/.ssh/authorized_keys
on the machine you want to log into.