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.byhost 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.byuser 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 independent 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 considerable 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