NAME
revnetgroup —
generate reverse netgroup
data
SYNOPSIS
revnetgroup |
-u | -h
[-f netgroup_file] |
DESCRIPTION
Therevnetgroup 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
-uor-hflags must be specified.) - [
-fnetgroup_file] - The
revnetgrouputility uses /etc/netgroup as its default input file. The-fflag allows the user to specify an alternate input file. Specifying ``-'' as the input file causesrevnetgroupto read from the standard input.
FILES
- /var/yp/Makefile
- the Makefile that calls
yp_mkdbandrevnetgroupto 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
AUTHORS
Bill Paul <wpaul@ctr.columbia.edu>