| REVNETGROUP(8) | System Manager's Manual | REVNETGROUP(8) | 
revnetgroup —
| revnetgroup | [ -hu] [-fnetgroup_file] | 
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
  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 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 command prints its results
    on the standard output. It is usually called only by
    /var/yp/<domain>/Makefile when rebuilding the
    NIS netgroup maps.
revnetgroup command supports the following options:
-u-h-u or -h flags must be
      specified.)-f netgroup_file]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.makedbm and
      revnetgroup to build the NIS databases.| February 26, 2005 | NetBSD 10.1 |