The 'Secure Shell' protocol provides access to your Ubuntu Appliance and uses cryptographic keys to authenticate you to the device. You will need SSH software and keys.

Terminal is the terminal emulator which provides a text-based command-line interface (CLI) to the Unix shell of macOS.

To open the macOS Terminal:

1. In Finder, select Utilities from the Applications folder.
2. Find Terminal in the utilities list.

3. Enter the following command:

   ssh-keygen -t rsa

   This starts the key generation process. When you execute this command, the ssh-keygen utility prompts you to indicate where to store the key

4. Press the ENTER key to accept the default location. The ssh-keygen utility prompts you for a passphrase
5. Type in a passphrase

You now have a public and private key that you can use to authenticate.

Your private key is saved to the id_rsa file in the .ssh directory and is used to verify the public key you use belongs to the same account.