SSH - Key exclusive access

Make sure your SSH key’s public key is present in the .ssh/authorized_keys file of the user you want to use them for:

• /home/user/.ssh/authorized_keys for a normal user
• /root/.ssh/authorized_keys for root

Furthermore, make sure the directory and files have the correct permissions.

chmod 700 .ssh
chmod 600 .ssh/authorized_keys

Test your access to the server using your SSH key (identity file) as a parameter to -i

ssh -i ~/.ssh/your_private_key username@host

Danger

Make 100% sure you have configured and tested your access to the server using SSH keys sufficiently before proceeding!

You can most definitely lose access to your server. Especially if you don’t have physical access to it. It might be recoverable with the help of your hosting provider, but it might also be unrecoverable.

Create a new file in the /etc/ssh/sshd_config.d/ directory, to disable any access through passwords.

PasswordAuthentication no
PermitRootLogin prohibit-password

Then restart sshd

sudo systemctl restart sshd

or even better, restart your system

sudo systemctl reboot