NetBSD/share/man/man5/group.5

.\"	$NetBSD: group.5,v 1.5 1997/02/01 02:46:38 ghudson Exp $
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.\"     @(#)group.5	8.3 (Berkeley) 4/19/94
.\"
.Dd July 18, 1995
.Dt GROUP 5
.Os
.Sh NAME
.Nm group
.Nd format of the group permissions file
.Sh DESCRIPTION
The file
.Aq Pa /etc/group
consists of newline separated
.Tn ASCII
records, one per group, containing four colon
.Ql \&:
separated fields. These fields are as follows:
.Bl -tag -width password -offset indent -compact
.It group
Name of the group.
.It passwd
Group's
.Em 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
.Em 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
.Pp
The group with gid 0 has a special meaning to the 
.Xr su 1
command: if it exists and has any members, only users in that group
are allowed to
.Nm su
to
.Dq root .
.Sh YP SUPPORT
If YP is active, the
.Nm
file may also contain lines of the format
.Pp
.Bl -tag -offset indent -compact
+name:*::
.Pp
which causes the specified group to be included from the
.Pa group.byname
YP map.
.Pp
If no group name is specified, or the ``+'' (plus sign) appears alone
on line, all groups are included from the YP map.
.Pp
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
.Nm
file itself, or included via YP, will be used.
.Sh FILES
.Bl -tag -width /etc/group -compact
.It Pa /etc/group
.El
.Sh SEE ALSO
.Xr setgroups 2 ,
.Xr initgroups 3 ,
.Xr crypt 3 ,
.Xr passwd 1 ,
.Xr passwd 5 ,
.Xr yp 8
.Sh BUGS
The
.Xr passwd 1
command does not change the
.Nm group
passwords.
.Sh HISTORY
A
.Nm
file format appeared in
.At v6 .
.Pp
YP file format first appeared in SunOS.