Before you enable Google Authenticator you will need to download the Google Authenticator App for your smart phones, tablets or web browser. The App is available for Android, iOS devices as well as browser extension like Chrome Authenticator or Firefox Authenticator extension.

Once you have an Google Authenticator App, you can now enable google authenticator feature to enable two factor authentication on CS Linux machines simply by typing: google-authenticator in a terminal window and answer 'y' on each questions as below:

% google-authenticator


Do you want authentication tokens to be time-based (y/n) y
https://www.google...@YOURHOSTNAME%3Fsecret%3DWYD4SYCGEE5N4M3LA

Your new secret key is: WYD4SYCGEE5N4M3LA
Your verification code is 163127
Your emergency scratch codes are:
  40186300
  18418071
  87502143
  30873576
  00892542

Do you want me to update your "/path/homedir/.google_authenticator" file (y/n) y

Do you want to disallow multiple uses of the same authentication
token? This restricts you to one login about every 30s, but it increases
your chances to notice or even prevent man-in-the-middle attacks (y/n) y

By default, tokens are good for 30 seconds and in order to compensate for
possible time-skew between the client and the server, we allow an extra
token before and after the current time. If you experience problems with poor
time synchronization, you can increase the window from its default
size of 1:30min to about 4min. Do you want to do so (y/n) y

If the computer that you are logging into isn't hardened against brute-force
login attempts, you can enable rate-limiting for the authentication module.
By default, this limits attackers to no more than 3 login attempts every 30s.
Do you want to enable rate-limiting (y/n) y

At this time you can use your your Google Authenticator and scan the code you see on the screen or copy/paste the link you see to a browser to verify and complete the activation.

To test your Google Authenticator, open a new ssh session and enter your username. The prompt will ask you for a verification code and then your password. Make sure you enter your Google Authenticator code when you are asked for verification code. If you make a mistake, you have to do it all over again. The code can only be used once. Make sure you wait for a new verification code before you enter it.

Note: On an SSH session, the verification code is asked before your password, otherwise, verification code will be asked after your password is entered.

• If you would like to use just 1 authenticator code for all CS Linux System, you can copy the .google-authenticator file to your home directory to each cluster. When google authenticator is enabled on the machine, it will automatically take effect.
• If for some reasons you need to turn off google authenticator, simply remove .google-authenticator file and it will no longer work.