-<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
-<!--
- This file is part of systemd.
-
- Copyright 2011 Lennart Poettering
- Copyright 2013 Tom Gundersen
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd 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
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
-
-<refentry id="nss-resolve" conditional='ENABLE_RESOLVED'>
+<refentry id="nss-resolve" conditional='ENABLE_NSS_RESOLVE'>
<refentryinfo>
<title>nss-resolve</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<refsect1>
<title>Description</title>
- <para><command>nss-resolve</command> is a plugin module for the
- GNU Name Service Switch (NSS) functionality of the GNU C Library
- (<command>glibc</command>) enabling it to resolve host names via
- the
- <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- local network name resolution service.</para>
-
- <para>To activate the NSS module, <literal>resolve</literal>
- has to be added to the line starting with
- <literal>hosts:</literal> in
- <filename>/etc/nsswitch.conf</filename>.</para>
-
- <para>It is recommended to place <literal>resolve</literal> early
- in the <filename>nsswitch.conf</filename> line (but after the
- <literal>files</literal> entry), replacing the
- <literal>dns</literal> entry if it exists, to ensure DNS queries
+ <para><command>nss-resolve</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of the
+ GNU C Library (<command>glibc</command>) enabling it to resolve host names via the
+ <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry> local network
+ name resolution service. It replaces the <command>nss-dns</command> plug-in module that traditionally resolves
+ hostnames via DNS.</para>
+
+ <para>To activate the NSS module, add <literal>resolve</literal> to the line starting with
+ <literal>hosts:</literal> in <filename>/etc/nsswitch.conf</filename>. Specifically, it is recommended to place
+ <literal>resolve</literal> early in <filename>/etc/nsswitch.conf</filename>'s <literal>hosts:</literal> line (but
+ after the <literal>files</literal> or <literal>mymachines</literal> entries), right before the
+ <literal>dns</literal> entry if it exists, followed by <literal>[!UNAVAIL=return]</literal>, to ensure DNS queries
are always routed via
- <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
+ <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry> if it is
+ running, but are routed to <command>nss-dns</command> if this service is not available.</para>
+
+ <para>Note that <command>systemd-resolved</command> will synthesize DNS resource
+ records in a few cases, for example for <literal>localhost</literal> and the
+ current hostname, see
+ <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for the full list. This duplicates the functionality of
+ <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ but it is still recommended (see examples below) to keep
+ <command>nss-myhostname</command> configured in
+ <filename>/etc/nsswitch.conf</filename>, to keep those names resolveable if
+ <command>systemd-resolved</command> is not running.</para>
</refsect1>
<refsect1>
<title>Example</title>
- <para>Here is an example <filename>/etc/nsswitch.conf</filename>
- file that enables <command>resolve</command> correctly:</para>
+ <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables <command>nss-resolve</command>
+ correctly:</para>
-<programlisting>passwd: compat mymachines
-group: compat mymachines
+ <!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
+<programlisting>passwd: compat mymachines systemd
+group: compat mymachines systemd
shadow: compat
-hosts: files <command>resolve</command> mymachines myhostname
+hosts: files mymachines <command>resolve [!UNAVAIL=return]</command> dns myhostname
networks: files
protocols: db files
rpc: db files
netgroup: nis</programlisting>
-
- <para>Note that <command>nss-resolve</command> will chain-load
- <command>nss-dns</command> if
- <filename>systemd-resolved.service</filename> is not running,
- ensuring that basic DNS resolution continues to work if the
- service is down.</para>
-
</refsect1>
<refsect1>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
projects / thirdparty / systemd.git / blobdiff