Groups

Groups
Groups are simple collections of users. They are used primarily to simply permission assignment, and thus grant or deny access to multiple users at once.

Groups are usually, but not always, assigned based on administrative or business policies. There are few explicit requirements for using groups in the "system administration" sense.

One notable exception to this is the "wheel" group, frequently found in BSD. There are various implementations concerning this group, but typically, only users in this group are allowed to use the su command to become root.

NGROUP_MAX
Each operating system has a maximum number of groups to which a single user may belong. (Note that this is 'not' the same as "what is the maximum size of a group").