Setting up 2 factor authentication for ssh logins on Ubuntu 16.04
totp may be deployed so you can use your Google Authenticator, FreeOTP or similar, to add a layer of security to your ssh logins.
This guide worked for me (Linode):
Use One-Time Passwords for Two-Factor Authentication with SSH on Ubuntu 16.04 and Debian 8
While this guide did not enable totp for me: