Tutorial: Adding an SSH Key to a Server

In this tutorial, we will guide you through the process of adding an SSH key to a server, which enhances the security of your server by allowing secure, passwordless access. If you don't have an SSH key yet, we'll also show you how to create one.

Prerequisites:

• A terminal or command prompt to run commands.
• Access to the server you want to add your SSH key to.
• Basic knowledge of using the command line.

Part 1: Creating a SSH Key                                                      

1. Open your terminal (or command prompt if you are using Windows).

2. To generate an SSH key pair, simply run the following command: “ssh-keygen”

3. You'll be prompted to choose a location to save the key pair. Press Enter to accept the default location, which is usually ~/.ssh/id_rsa for the private key and ~/.ssh/id_rsa.pub for the public key.

4. Optionally, you can set a passphrase for extra security. This adds an extra layer of protection to your private key.

5. Your SSH key pair has been generated. You can find your public key in the ~/.ssh/id_rsa.pub Open it with a text editor and copy the entire key.

Part 2: Adding Your SSH Key to the Server

1. Log in to your server using your preferred method (e.g., username and password). Ensure you have the necessary permissions to add SSH keys to the server.

2. First, make sure the .ssh directory exists in your home directory. You can create it if it doesn't already exist by running: “mkdir -p ~/.ssh “

3. Next, open the authorized_keys file in the .ssh directory using a text editor like nano. If the file doesn't exist, it will be created: “nano ~/.ssh/authorized_keys”

4. Inside the authorized_keys file, you should paste your public key. To make it easy to identify, add a comment at the beginning of the line. It typically looks like this:

#Your Name

<paste your public key here>

5. Save the file and exit the text editor. In nano, you can do this by pressing Ctrl + X, then Y to confirm the changes, and Enter to save.
   
   
6. To enhance security, disable password-based authentication and enforce key-based authentication. Open the SSH server configuration file in an editor:
   “sudo nano /etc/ssh/sshd_config”

7. Look for the line that says PasswordAuthentication. Uncomment the line (remove the # if present) and change its value to no like this:
   PasswordAuthentication no

8. Save the file and exit the text editor (in nano, it's Ctrl + X, then Y, and Enter).
9. Finally, restart the SSH service to apply the changes: “sudo systemctl restart ssh”

Congratulations! You've successfully added an SSH key to your server and disabled password-based authentication.

You can now log in to your server securely using your SSH key.

Remember to keep your private key secure and never share it.