GROUP(5)

NAME
group - format of the group permissions file

DESCRIPTION
The file /etc/group consists of newline separated ASCII records, one per group, containing four colon (‘’): separated fields. These fields are as follows:

group
    Name of the group.
passwd
    Group's encrypted password.
gid The group's decimal ID.
member
    Group members.

The group field is the group name used for granting file access to users who are members of the group. The gid field is the number associated with the group name. They should both be unique across the system (and often across a group of systems) since they control file access. The passwd field is an optional encrypted password. This field is rarely used and an asterisk is normally placed in it rather than leaving it blank. The member field contains the names of users granted the privileges of group. The member names are separated by commas without spaces or newlines. A user is automatically in a group if that group was specified in their passwd(5) entry and does not need to be added to that group in the group file.

YP SUPPORT
If YP is active, the group file also supports YP exclusions and inclusions.

Lines beginning with a ‘-’ (minus sign) are entries marked as being excluded from any following inclusions, which are marked with a `+' (plus sign).

Lines of the format

    +name:*::

cause the specified group to be included from the group.byname YP map. If no group name is specified, or the ‘+’ (plus sign) appears alone on a line, all groups are included from the YP map.

YP references may appear anywhere in the file, but the single ‘+’ form should be on the last line, for historical reasons. Only the first group with a specific name encountered, whether in the group file itself, or included via YP, will be used.

Proper YP group support requires consistent group.byname, group.bygid and netid.byname YP maps. See getgrent(3) and getgrouplist(3) for details.

When YP is enabled but temporarily unavailable, login becomes impossible for all users except those having an entry in the netid(5) file.

FILES
/etc/group

SEE ALSO
passwd(1), setgroups(2), crypt(3), initgroups(3), netid(5), passwd(5), yp(8)

HISTORY
The group file format first appeared in AT&T UNIX.

The YP file format first appeared in SunOS.

BUGS
The passwd(1) command does not change the group passwords.

Lines in /etc/group are limited to 1024 characters. YP groups are not affected by this limit.

Groups are limited to a maximum of 200 members per group.