google-authenticatorはコマンドオプションで非対話でやれるけど
とりあえず素で実行。全部yでおk。
# useradd vpnuser01
# passwd vpnuser01
# su vpnuser01
# google-authenticator
Do you want authentication tokens to be time-based (y/n) y
https://www.google.com/chart?chs=200x200&chld=M|0&cht=qr&chl=otpauth://totp/vpnuser01@[サーバー名]%3Fsecret%3XXXXXXXXXXXXXXXXX
Your new secret key is: XXXXXXXXXXXXXXXX
Your verification code is XXX
Your emergency scratch codes are:
XXXXXXXX
XXXXXXXX
XXXXXXXX
XXXXXXXX
XXXXXXXX
Do you want me to update your "/home/vpnuser01/.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
IIJ SmartKeyとかで上記のURLに表示されるQRコードを読み込む
※Google純正のやつでもいいけど、ロックができないから微妙。