B
Each user belongs to a group that is referred to as the users primary group. The GID number, located in the users account entry within the /etc/passwd file, specifies the users primary group. Each user can also belong to up to 15 additional groups, known as secondary groups. In the /etc/group file, you can add users to group entries, thus establishing the users secondary group affiliations. Note (4 PSARC/2009/542): his project proposes changing the maximum value for NGROUPS_MAX from 32 to 1024 by changing the definition of NGROUPS_UMAX from 32 to 1024. The use for a larger number of groups is described in CR 4088757, particular in the case of Samba servers and ADS clients; the Samba servers map every SID to a Unix group. Users with more than 32 groups SIDs are common. We`ve seen reports varying from "64 is enough", "128 is absolutely enough" and "we`ve users with more 190 group SIDS). NGROUPS_MAX as defined by different Unix versions are as follows (http://www.j3e.de/ngroups.html): Linux Kernel >= 2.6.3 65536 - Linux Kernel < 2.6.3 32 - Tru64 / OSF/1 32 - IBM AIX 5.2 64 - IBM AIX 5.3 ... 6.1 128 - OpenBSD, NetBSD, FreeBSD, Darwin (Mac OS X) 16 Sun Solaris 7, 8, 9, 10 16 (can vary from 0-32) HP-UX 20 - IRIX 16 (can vary from 0-32) Plan 9 from Bell Labs 32 - Minix 3 0 (Minix-vmd: 16) QNX 6.4 8