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\"     @(#)group.5      8.3 (Berkeley) 4/19/94
\"
Dd June 21, 2007
Dt GROUP 5
Os
Sh NAME
Nm group
Nd format of the group permissions file
Sh DESCRIPTION
The
Nm
file
Pa /etc/group
is the local source of group information.
It can be used in conjunction with the Hesiod domain
Sq group ,
and the
Tn NIS
maps
Sq group.byname
and
Sq group.bygid ,
as controlled by
Xr nsswitch.conf 5 .
Pp
The
Nm
file consists of newline separated
Tn ASCII
records, usually one per group, containing four colon
Ql \&:
separated fields.
Each line has the form:
Dl group:passwd:gid:[member[,member]...]
Pp
These fields are as follows:
Bl -tag -width password -offset indent -compact
It Em group
Name of the group.
It Em passwd
Group's
Em encrypted
password.
It Em gid
The group's decimal ID.
It Em member
Group members.
El
Pp
The
Em group
field is the group name used for granting file access to users
who are members of the group.
Pp
The
Em 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.
Pp
The
Em 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.
Pp
The
Em member
field contains the names of users granted the privileges of
Em 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
Very large groups can be accommodated over multiple lines by specifying the
same group name in all of them; other than this, each line has an identical
format to that described above.
This can be necessary to avoid the record's length limit, which is currently
set to 1024 characters.
Note that the limit can be queried through
Xr sysconf 3
by using the
Li _SC_GETGR_R_SIZE_MAX
parameter.
For example:
Bd -literal -offset indent
biggrp:*:1000:user001,user002,user003,...,user099,user100
biggrp:*:1000:user101,user102,user103,...
Ed
Pp
The group with the name
Dq wheel
has a special meaning to the
Xr su 1
command: if it exists and has any members, only users listed in that group
are allowed to
Nm su
to
Dq root .
Sh HESIOD SUPPORT
If
Sq dns
is specified for the
Sq group
database in
Xr nsswitch.conf 5 ,
then
Nm
lookups occur from the
Sq group
Hesiod domain.
Sh NIS SUPPORT
If
Sq nis
is specified for the
Sq group
database in
Xr nsswitch.conf 5 ,
then
Nm
lookups occur from the
Sq group.byname
and
Sq group.bygid
Tn NIS
map.
Sh COMPAT SUPPORT
If
Sq compat
is specified for the
Sq group
database, and either
Sq dns
or
Sq nis
is specified for the
Sq group_compat
database in
Xr nsswitch.conf 5 ,
then the
Nm
file may also contain lines of the format
Pp
+name:*::
Pp
which causes the specified group to be included from the
Sq group
Hesiod domain
or the
Sq group.byname
Tn NIS
map (respectively).
Pp
If no group name is specified, or the plus sign
Pq Dq \&+
appears alone
on line, all groups are included from the
Hesiod domain or the
Tn NIS
map.
Pp
Hesiod or
Tn NIS
compat references may appear anywhere in the file, but the single
plus sign
Pq Dq \&+
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 Hesiod or
Tn NIS ,
will be used.
Sh FILES
Bl -tag -width /etc/group -compact
It Pa /etc/group
El
Sh SEE ALSO
Xr newgrp 1 ,
Xr passwd 1 ,
Xr su 1 ,
Xr setgroups 2 ,
Xr crypt 3 ,
Xr initgroups 3 ,
Xr nsswitch.conf 5 ,
Xr passwd 5 ,
Xr yp 8
Sh HISTORY
A
Nm
file format appeared in
At v6 .
Pp
The
Tn NIS
file format first appeared in SunOS.
Pp
The Hesiod support first appeared in
Nx 1.4 .
Sh BUGS
The
Xr passwd 1
command does not change the
Nm group
passwords.

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