Secure a new VPS: users, keys and firewall

Create an admin user

adduser deploy
usermod -aG sudo deploy

Use an SSH key

1. On your computer run ssh-keygen -t ed25519.
2. Copy the key with ssh-copy-id deploy@YOUR.SERVER.IP.
3. Test the login in a new window before the next step.

Close the door

Set PasswordAuthentication no and PermitRootLogin no in /etc/ssh/sshd_config, then restart SSH. Next enable the firewall:

ufw allow OpenSSH
ufw allow 80,443/tcp
ufw enable