This tutorial describes how to set up two-factor authentication for an SSH server by integrating Google Authenticator with OpenSSH. Install Google Authenticator on Linux The first step is to install Google Authenticator on your Linux host. You can do this by running the following command: sudo apt-get install google-authenticator Configure Google Authenticator Once installed, you can configure Google Authenticator by running the following command: google-authenticator You will be prompted to enter a secret key. Make a note of this key, as you will need it later. Configure OpenSSH To configure OpenSSH to use Google Authenticator, you need to create a new file in the /etc/pam.d directory. You can do this by running the following command: sudo nano /etc/pam.d/sshd Add the following lines to the end of the file: auth required pam_google_authenticator.so Save and close the file. Then, restart the SSH server by running the following command: sudo service ssh restart Use Google Authenticator To use Google Authenticator, you will need to generate a one-time passcode on your Android device. You can do this by opening the Google Authenticator app and scanning the QR code that was generated during the configuration process. Enter the one-time passcode on your Linux host, and you will be logged in to your SSH server. Summary: This tutorial describes how to set up two-factor authentication for an SSH server by integrating Google Authenticator with OpenSSH.