OpenBSD-4.6/share/man/man5/group.5

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.\"	$OpenBSD: group.5,v 1.14 2009/06/03 16:02:44 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.
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.\"     @(#)group.5	8.3 (Berkeley) 4/19/94
.\"
.Dd $Mdocdate: June 3 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 also supports YP exclusions and inclusions.
.Pp
Lines beginning with a
.Ql \&-
(minus sign) are entries marked as being excluded from any following
inclusions, which are marked with a `+' (plus sign).
.Pp
Lines of the format
.Bd -literal -offset indent
+name:*::
.Ed
.Pp
cause 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.