Force SSH login to be key file only

How to force SSH key only access to your Linux system with password access being denied.

Creating SSH key access to Linux instead of a password.

Open the sshd config file for editing:

nano /etc/ssh/sshd_config

Find and set/ensure the following have these values:

PasswordAuthentication no
PubkeyAuthentication yes
UsePAM no
ChallengeResponseAuthentication no

Note Being commented out has no effect, it must be stated

#PasswordAuthentication no

Make sure it is:

PasswordAuthentication no

Press control + x then y and then enter to save.

Now restart the sshd service with:

service ssh restart

It is always best to check before you close the session that the sshd service accepts your key file, do this by opening up a new ssh session connecting with your private key file.