NAME
revnetgroup —
generate reverse netgroup
data
SYNOPSIS
revnetgroup |
-u [-f
netgroup_file] |
revnetgroup |
-h [-f
netgroup_file] |
DESCRIPTION
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/Makefile when rebuilding the NIS netgroup
maps.
OPTIONS
The revnetgroup command 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
revnetgroupcommand 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>