sysvgroups/bsdgroups

grpid or bsdgroups / nogrpid or sysvgroups
These options define what group id a newly created
file gets. When grpid is set, it takes the group
id of the directory in which it is created; other╜
wise (the default) it takes the fsgid of the cur╜
rent process, unless the directory has the setgid
bit set, in which case it takes the gid from the
parent directory, and also gets the setgid bit set
if it is a directory itself.