REVNETGROUP(8)          OpenBSD System Manager's Manual         REVNETGROUP(8)

NAME
     revnetgroup - generate reverse netgroup data

SYNOPSIS
     revnetgroup -h | -u [-f netgroup_file]

DESCRIPTION
     revnetgroup processes the contents of a file in netgroup(5) format into
     what is called reverse netgroup form.  That is, where the original file
     shows netgroup memberships in terms of which members reside in a particu-
     lar group, the reverse netgroup format specifies what groups are associ-
     ated with a particular member.  This information is used to generate the
     netgroup.byuser and netgroup.byhosts YP maps.  These reverse netgroup
     maps are used to help speed up netgroup lookups, particularly for the
     innetgr() library function.

     For example, the standard /etc/netgroup file may list a netgroup and a
     list of its members.  Here, the netgroup is considered the key and the
     member names are the data.  By contrast, the reverse netgroup.byusers
     database lists each unique member as the key and the netgroups to which
     the members belong become the data.  Separate databases are created to
     hold information pertaining to users and hosts; this allows netgroup
     username lookups and netgroup hostname lookups to be performed using in-
     dependent keyspaces.

     By constructing these reverse netgroup databases (and the corresponding
     YP maps) in advance, the getnetgrent(3) library functions are spared from
     having to work out the dependencies themselves on the fly.  This is im-
     portant on networks with large numbers of users and hosts, since it can
     take a considerable amount of time to process very large netgroup
     databases.

     The revnetgroup command prints its results on the standard output.  It is
     usually called only by /var/yp/<domain>/Makefile when rebuilding the YP
     netgroup maps.

     The options are as follows:

     -f netgroup_file
             The revnetgroup command uses /etc/netgroup as its default input
             file.  The -f flag allows the user to specify an alternate input
             file.  Specifying ``-'' as the input file causes revnetgroup to
             read from the standard input.

     -h      Generate netgroup.byhost output; only hostname information in the
             original netgroup file is processed.

     -u      Generate netgroup.byuser output; only username information in the
             original netgroup file is processed.

FILES
     /var/yp/<domain>Makefile  The Makefile that calls makedbm(8) and
                               revnetgroup to build the YP databases.
     /etc/netgroup             The default netgroup database file.  This file
                               is most often found only on the YP master serv-
                               er.

SEE ALSO
     getnetgrent(3), netgroup(5), makedbm(8), yp(8)

AUTHORS
     Bill Paul <wpaul@ctr.columbia.edu>

OpenBSD 4.7                    October 20, 2009                              1
