user's login session limit

[chengjianwen]

How can I limit the user login session?
I means one user can login on multi host at same time. I don't want that.
Thanks

[maxnet]

That is not really a supported feature.

At the authentication stage it can only check if username/password is correct, and does not know anything about if user is already logged in somewhere or not.
You do may be able to deny the user access to his home directory if logged in more than once (through pam_limits and maxlogins in /etc/security/limits.conf on the server), but that may lock out your user as well if network connectivity is ever interrupted, and the system thinks the user is already logged in, while the previous connection is no longer usable.
Would not recommend it.