Implementing Google-Authenticator for SSH

#linux

CentOS

yum install epel-release
yum install google-authenticator

Edit /etc/pam.d/sshd add auth required pam_google_authenticator.so as the second line (or first method of auth near the top)

Edit /etc/ssh/sshd_config and make sure ChallengeResponseAuthentication yes is set.

Run google-authenticator as your user to set the TOTP and choose various options for it.