SSH

For remote work use public key authentication. Therefore we have to initially permit root access with password.

sudo nano /etc/ssh/sshd_config

Add PermitRootLogin yes and reboot.

Copy public key to the Raspberry Pi

cat ~/.ssh/id_rsa.pub | ssh root@alpha "mkdir .ssh && cat - >> ~/.ssh/authorized_keys"

Test ssh login

ssh root@alpha

Change sshd_config

PermitRootLogin prohibit-password
PubkeyAuthentication yes