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Portions Copyright(c) 1994, Jason Downs. All rights reserved.
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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
a /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 .
p 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]...]
p These fields are as follows: l -tag -width password -offset indent -compact t Em group Name of the group. t Em passwd Group's .Em encrypted password. t Em gid The group's decimal ID. t Em member Group members. .El
p The .Em group field is the group name used for granting file access to users who are members of the group.
p 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.
p 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.
p 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
a /etc/passwd entry and does not need to be added to that group in the
p 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: d -literal -offset indent biggrp:*:1000:user001,user002,user003,...,user099,user100 biggrp:*:1000:user101,user102,user103,... .Ed
p 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
p +name:*::
p which causes the specified group to be included from the .Sq group Hesiod domain or the .Sq group.byname .Tn NIS map (respectively).
p If no group name is specified, or the plus sign
q Dq + appears alone on line, all groups are included from the Hesiod domain or the .Tn NIS map.
p Hesiod or .Tn NIS compat references may appear anywhere in the file, but the single plus sign
q 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 l -tag -width /etc/group -compact t 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 .
p The .Tn NIS file format first appeared in SunOS.
p The Hesiod support first appeared in .Nx 1.4 . .Sh BUGS The .Xr passwd 1 command does not change the .Nm group passwords.
Indexes created Sat Sep 20 22:09:52 GMT 2025