For a very secure and convenient way to add two-factor ssh auth to your Linux server, you can use Google Authenticator. I’ll show you how to set this up!

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1. In Ubuntu 13.04:

$ sudo apt-get install libpam-google-authenticator

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2. Then, from an open bash shell with your user account on that server and run the following:

$ google-authenticator

Scan the bar code with your Android phone to add the key. (Or alternatively, open the URL provided on your phone to add the key.)

Note: save the emergency scratch codes in case you need to access the server without your phone!

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