Ubuntu 20.04 - 콘솔, SSH에 Google OTP 적용

sudo apt update
sudo apt upgrade -y
sudo apt install libpam-google-authenticator -y
sudo vi /etc/pam.d/common-auth *수정

auth required pam_google_authenticator.so nullok

google-authenticator *실행, 다음 모두 y
update your file
disallow multiple uses of the same authentication
allow an extra token
enable rate-limiting