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

     revnetgroup -- generate reverse netgroup data

     revnetgroup -u | -h [-f netgroup_file]

     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 in-
     dependent 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 data-

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

     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.

     /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

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

     Bill Paul <>

FreeBSD	13.0		       October 24, 1995			  FreeBSD 13.0


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