Add Your Existing SSH Key To The Root User Account

So, you’ve provisioned a server but your host didn’t install an ssh key-pair for you. Which likely means that you’re just logging in with a password.

But, you do have an ssh key-pair already and instead of generating another one unique to your server, you would like to use the existing one.

The easiest way to do this is as follows:

• Log into your server using SSH as the user to which you want to add a key.
• Run the following command to open up the file containing the public keys for that user:

sudo nano ~/.ssh/authorized_keys

• Open up your existing public key on your local machine in any editor and copy it to the clipboard.
• Paste it into the nano editor (usually using the right-mouse-click button). If there is an existing key in there already, paste the new public key on a new line.
• Use ctrl-o to save the file.

Do NOT close your ssh session. Instead use a new ssh session to test your new login using your key-pair.

Note: By not closing the existing session you are still able to make changes – which is useful in case you get locked out for some reason. Once your login tests are complete and successful you can close the session.

Recommended: Prevent Root From Using A Password For Login

After you’ve confirmed that your root user can use your key-pair to login, you can disable the use of the password. This will force the root user to always use the key-pair for logins.

• Open up the sshd_config file:

sudo nano /etc/ssh/sshd_config

• Scroll down until you find the PasswordAuthentication option. Set it to “no”.
• Use ctrl-o to save the file.
• Restart the ssh server:

sudo systemctl reload ssh