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

NAME
     revnetgroup -- generate reverse netgroup data

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

DESCRIPTION
     The revnetgroup utility 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 particular group, the reverse netgroup format specifies what groups are associated
     with a particular member.  This information is used to generate the netgroup.byuser and
     netgroup.byhosts NIS 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 inde-pendent independent
     pendent keyspaces.

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

     The revnetgroup utility prints its results on the standard output.  It is usually called only by
     /var/yp/Makefile when rebuilding the NIS netgroup maps.

OPTIONS
     The revnetgroup utility supports the following options:

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

     -h      Generate netgroup.byhost output; only hostname information in the original netgroup file is
             processed.  (Note at least one of the -u or -h flags must be specified.)

     [-f netgroup_file]
             The revnetgroup utility 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.

FILES
     /var/yp/Makefile  the Makefile that calls yp_mkdb and revnetgroup to build the NIS databases
     /etc/netgroup     the default netgroup database file.  This file is most often found only on the NIS
                       master server

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

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

BSD                                           October 24, 1995                                           BSD