Интерактивная система просмотра системных руководств (man-ов)
revnetgroup (8)
>> revnetgroup (8) ( FreeBSD man: Команды системного администрирования )
revnetgroup (8) ( Linux man: Команды системного администрирования )
BSD mandoc
NAME
revnetgroup
- generate reverse netgroup data
SYNOPSIS
-u | h
[-f netgroup_file
]
DESCRIPTION
The
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.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
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
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
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
to read from the standard input.
FILES
/var/yp/Makefile
the Makefile that calls
yp_mkdb
and
to build the
NIS
databases
/etc/netgroup
the default netgroup database file.
This file is most often found
only on the
NIS
master server
