NAME
revnetgroup —
generate reverse netgroup
data
SYNOPSIS
revnetgroup |
[-hu]
[-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/<domain>/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
-u or -h flags must be
specified.)
-
-
- [-f
netgroup_file]
- The 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.
FILES
- /var/yp/<domain>/Makefile
- The Makefile that calls makedbm 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),
makedbm(8),
nis(8)
AUTHORS
Bill Paul
<
wpaul@ctr.columbia.edu>