.\"	$OpenBSD: group.5,v 1.13 2009/03/27 12:31:31 schwarze Exp $
.\"	$NetBSD: group.5,v 1.4 1995/07/28 06:41:39 phil Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\" Portions Copyright(c) 1994, Jason Downs. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)group.5	8.3 (Berkeley) 4/19/94
.\"
.Dd $Mdocdate: March 27 2009 $
.Dt GROUP 5
.Os
.Sh NAME
.Nm group
.Nd format of the group permissions file
.Sh DESCRIPTION
The file
.Pa /etc/group
consists of newline separated
.Tn ASCII
records, one per group, containing four colon
.Pq Ql \&:
separated fields.
These fields are as follows:
.Pp
.Bl -tag -width password -offset indent -compact
.It group
Name of the group.
.It passwd
Group's encrypted password.
.It gid
The group's decimal ID.
.It member
Group members.
.El
.Pp
The
.Ar group
field is the group name used for granting file access to users
who are members of the group.
The
.Ar 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
.Ar 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
.Ar member
field contains the names of users granted the privileges of
.Ar 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
.Pa /etc/passwd
entry and does not need to be added to that group in the
.Pa /etc/group
file.
.\" .Pp
.\" When the system reads the file
.\" .Pa /etc/group
.\" the fields are read into the structure
.\" .Fa group
.\" declared in
.\" .Aq Pa grp.h :
.\" .Bd -literal -offset indent
.\" struct group {
.\"	char    *gr_name;        /* group name */
.\"	char    *gr_passwd;      /* group password */
.\"	int     gr_gid;          /* group id */
.\"	char    **gr_mem;        /* group members */
.\" };
.\" .Ed
.Sh YP SUPPORT
If YP is active, the
.Nm
file may also contain lines of the format
.Bd -literal -offset indent
+name:*::
.Ed
.Pp
which causes the specified group to be included from the
.Pa group.byname
YP map.
If no group name is specified, or the
.Ql +
(plus sign) appears alone on a line, all groups are included from the YP map.
.Pp
YP references may appear anywhere in the file, but the single
.Ql +
form should be on the last line, for historical reasons.
Only the first group with a specific name encountered, whether in the
.Nm
file itself, or included via YP, will be used.
.Pp
Proper YP group support requires consistent
.Pa group.byname ,
.Pa group.bygid
and
.Pa netid.byname
YP maps.
See
.Xr getgrent 3
and
.Xr getgrouplist 3
for details.
.Pp
When YP is enabled but temporarily unavailable, login becomes impossible
for all users except those having an entry in the
.Xr netid 5
file.
.Sh FILES
.Bl -tag -width /etc/group -compact
.It Pa /etc/group
.El
.Sh SEE ALSO
.Xr passwd 1 ,
.Xr setgroups 2 ,
.Xr crypt 3 ,
.Xr initgroups 3 ,
.Xr netid 5 ,
.Xr passwd 5 ,
.Xr yp 8
.Sh HISTORY
A
.Nm
file format appeared in
.At v6 .
.Pp
The YP file format first appeared in SunOS.
.Sh BUGS
The
.Xr passwd 1
command does not change the
.Nm
passwords.
.Pp
Lines in
.Pa /etc/group
are limited to 1024 characters.
YP groups are not affected by this limit.
.Pp
Groups are limited to a maximum of 200 members per group.