group(5) - NetBSD Manual Pages

GROUP(5)                  NetBSD File Formats Manual                  GROUP(5)


NAME

     group -- format of the group permissions file


DESCRIPTION

     The group file /etc/group is the local source of group information.  It
     can be used in conjunction with the Hesiod domain `group', and the NIS
     maps `group.byname' and `group.bygid', as controlled by nsswitch.conf(5).

     The group file consists of newline separated ASCII records, usually one
     per group, containing four colon `:' separated fields.  Each line has the
     form:
           group:passwd:gid:[member[,member]...]

     These fields are as follows:
           group     Name of the group.
           passwd    Group's encrypted password.
           gid       The group's decimal ID.
           member    Group members.

     The group field is the group name used for granting file access to users
     who are members of the group.

     The 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 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 member field contains the names of users granted the privileges of
     group.  The member names are separated by commas without spaces or new-
     lines.  A user is automatically in a group if that group was specified in
     their /etc/passwd entry and does not need to be added to that group in
     the /etc/group file.

     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 sysconf(3) by using the
     _SC_GETGR_R_SIZE_MAX parameter.  For example:

           biggrp:*:1000:user001,user002,user003,...,user099,user100
           biggrp:*:1000:user101,user102,user103,...

     The group with the name ``wheel'' has a special meaning to the su(1) com-
     mand: if it exists and has any members, only users listed in that group
     are allowed to su to ``root''.


HESIOD SUPPORT

     If `dns' is specified for the `group' database in nsswitch.conf(5), then
     group lookups occur from the `group' Hesiod domain.


NIS SUPPORT

     If `nis' is specified for the `group' database in nsswitch.conf(5), then
     group lookups occur from the `group.byname' and `group.bygid' NIS map.


COMPAT SUPPORT

     If `compat' is specified for the `group' database, and either `dns' or
     `nis' is specified for the `group_compat' database in nsswitch.conf(5),
     then the group file may also contain lines of the format

     +name:*::

     which causes the specified group to be included from the `group' Hesiod
     domain or the `group.byname' NIS map (respectively).

     If no group name is specified, or the plus sign (``+'') appears alone on
     line, all groups are included from the Hesiod domain or the NIS map.

     Hesiod or NIS compat references may appear anywhere in the file, but the
     single plus sign (``+'') form should be on the last line, for historical
     reasons.  Only the first group with a specific name encountered, whether
     in the group file itself, or included via Hesiod or NIS, will be used.


FILES

     /etc/group


SEE ALSO

     newgrp(1), passwd(1), su(1), setgroups(2), crypt(3), initgroups(3),
     nsswitch.conf(5), passwd(5), yp(8)


HISTORY

     A group file format appeared in Version 6 AT&T UNIX.

     The NIS file format first appeared in SunOS.

     The Hesiod support first appeared in NetBSD 1.4.


BUGS

     The passwd(1) command does not change the group passwords.

NetBSD 7.1.2                     June 21, 2007                    NetBSD 7.1.2