ltiple Shell login by the same user on a Linux box you have to set a maximum number of logins in /etc/security/limits.conf for a user or a group.
For example:
# groupadd salesgroup
# useradd -G salesgroup salesman1
# useradd -G salesgroup salesmanager
# echo “@salesgroup – maxlogins 10? >> /etc/security/limits.conf
# echo “salesman1 – maxlogins 5? >> …