Disable SSH password login on Ubuntu

How to disable normal username/password login authentication to your Ubuntu server, only allowing SSH key authentication. This gives you the advantages of SSH’s whilst securing your server that little bit more.

Open the SSH config to edit its values:

sudo nano /etc/ssh/sshd_config

Find the parameter PasswordAuthentication and set it to no

PasswordAuthentication no

Next find ChallengeResponseAuthentication and set it to no

ChallengeResponseAuthentication no

Save these changes with ctrl + x and then enter.

Finally, reload the SSH server

sudo systemctl reload ssh

You will now no longer be able to long with a username and password, Only SSH keys will work.