.\" A man page for /etc/default/nss. -*- nroff -*-

.\"

.\" Copyright (C) 2006 Red Hat, Inc. All rights reserved.

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.\" modify, copy, or redistribute it subject to the terms and conditions of the

.\" GNU General Public License v.2.

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.\" This program is distributed in the hope that it will be useful, but WITHOUT

.\" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

.\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for

.\" more details.

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.\" You should have received a copy of the GNU General Public License along

.\" with this program; if not, write to the Free Software Foundation, Inc.,

.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

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.\" Author: Ulrich Drepper <drepper@redhat.com>

.TH nss 5 "May 2006" nss

.SH NAME

nss \- Name Service Switch configuration file

.SH DESCRIPTION

Each call to a function which retrieves data from a system database

like the password or group database is handled by the Name Service

Switch implementation in the GNU C library.  The various services

provided are implemented by independent modules, each of which

naturally varies widely from the other.

.PP

The default implementations coming with the GNU C library are by

default conservative and do not use unsafe data.  This might be

very costly in some situations, especially when the databases

are large.  Some modules allow the system administrator to request

taking shortcuts if these are known to be safe.  It is then the

system administrator's responsibility to ensure the assumption

is correct.

.PP

There are other modules where the implementation changed over time.

If an implementation used to sacrifize speed for memory consumption

it might create problems if the preference is switched.

.PP

The \fI/etc/default/nss\fR file contains a number of variable

assignments.  Each variable controls the behavior of one or more

NSS modules.  White spaces are ignored.  Lines beginning with `#'

are treated as comments.

.PP

The variables currently recognized are:

.TP

\fBNETID_AUTHORITATIVE =\fR \fITRUE\fR|\fIFALSE\fR

If set to TRUE, the NIS backend for the

.BR initgroups (3)

function will accept the information

from the netid.byname NIS map as authoritative.  This can speed up the

function significantly if the group.byname map is large.  The content

of the netid.byname map is used \fBas is\fR.  The system administrator has

to make sure it is correctly generated.

.TP

\fBSERVICES_AUTHORITATIVE =\fR \fITRUE\fR|\fIFALSE\fR

If set to TRUE, the NIS backend for the

.BR getservbyname (3)

and

.BR getservbyname_r (3)

function will assume

services.byservicename NIS map exists and is authoritative, particularly

that it contains both keys with /proto and without /proto for both

primary service names and service aliases.  The system administrator

has to make sure it is correctly generated.

.TP

\fBSETENT_BATCH_READ =\fR \fITRUE\fR|\fIFALSE\fR

If set to TRUE, the NIS backend for the

.BR setpwent (3)

and

.BR setgrent (3)

functions will read the entire

database at once and then hand out the requests one by one from

memory with every corresponding

.BR getpwent (3)

or

.BR getgrent (3)

call respectively.  Otherwise each

.BR getpwent (3)

or

.BR getgrent (3)

call might result into a network communication with the server to get

the next entry.

.SH EXAMPLE

The default configuration corresponds to the

following configuration file:

.nf

NETID_AUTHORITATIVE=FALSE

SERVICES_AUTHORITATIVE=FALSE

SETENT_BATCH_READ=FALSE

.SH FILES

\fI/etc/default/nss\fR

.SH AUTHOR

Ulrich Drepper <drepper@redhat.com>

.SH SEE ALSO

\fInsswitch.conf\fR