In Solaris, users must belong to a primary group, and are assigned to that group when their user accounts are set up. Primary group members usually have interests in common -- they might be an accounting group, a management group, or a group of engineers -- and would want to share files and directories.
If users have no special interests in common, they can be assigned to the default "staff" [group 10] group.
The primary group is the key to users being able to control access to their own files. The operating system assigns the same primary group identification (GID) number to all files created by members of the group. Each user can then specify who can access his or her files: the user only, members of the primary group, and users outside the primary group. (For more information, see Access to Files, Directories, and Tasks.)
Secondary Groups
In addition to the required membership in a primary group, each user may also be a member of up to 16 secondary groups. There is no inherent difference between primary and secondary groups. One user's primary group may be another user's secondary group.
While secondary group membership has no bearing on file access, some applications may consider a user's secondary group memberships in deciding whether to grant access to the application. For example, a system administration application may check to see if users are in the sysadmin group before allowing them to run the application.
In addition, users who log on as members of one primary group can use the newgrp command at a command line interface to change the GID assigned to all new files they create. In effect, this allows users to temporarily change their primary group to any other group of which they are a member.
Reserved Group ID Numbers
Groups with GIDs of 16 or less are system default Solaris Groups. They cannot be deleted but you can add users to them.
These include: root, GID 0; other, GID 1; bin, GID 2; mail, GID 6; staff, 10; and sysadmin, GID 14.
Solaris and Windows NT differ regarding the concept of "groups." See how groups differ.
To create a group, start Groups from the left side of the AdminSuite window, and click Action->Add Group.