Thanks to the Posix subsystem in NT a Windows User has a primary group in addition to the auxiliary groups. This script sets the primary group in the unix userdatase when an administrator sets the primary group from the windows user manager or when fetching a SAM with net rpc vampire. %u will be replaced with the user whose primary group is to be set. %g will be replaced with the group to set. /usr/sbin/usermod -g '%g' '%u'