What is the purpose of group "wheel" on FreeBSD (FreeNAS) OS?
It's in the
su(1) man page.
PAM is used to set the policy su(1) will use. In particular, by default only users in the "wheel" group can switch to UID 0 ("root"). This group requirement may be changed by modifying the "pam_group" section of /etc/pam.d/su. See pam_group(8) for details on how to modify this set- ting.
A very ancient version of the man page said:
Only users who are a member of group 0 (normally "wheel") can su to "root". If group 0 is missing or empty, any user can su to "root".
This allows you to control which users can
su. It is not likely that you want every single user of your system to be able to