systemd/man/nss-resolve.xml
Lennart Poettering 9053aaad42 man: change recommended order of NSS modules in /etc/nsswitch.conf
So far we recommended placing "nss-mymachines" after "nss-resolve" in the order
of preference in /etc/nsswitch.conf. This change reverse this order.

Rationale: single-label names are resolved via LLMNR by resolved, which has to
time out if no peer by that name exists. By placing "nss-mymachines" first
(which always responds immediately) we avoid running into this timeout for most
containers. Both modules should return the same data if LLMNR is used by the
container anyway.

While we are at it, improve the man pages of the three NSS modules in other
ways a bit.
2016-02-23 18:26:35 +01:00

112 lines
4.3 KiB
XML

<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
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
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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'>
<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>
<refentrytitle>nss-resolve</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>nss-resolve</refname>
<refname>libnss_resolve.so.2</refname>
<refpurpose>Provide hostname resolution via <filename>systemd-resolved.service</filename></refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>libnss_resolve.so.2</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<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>.</para>
<para>It is recommended to place <literal>resolve</literal> early in <filename>/etc/nsswitch.conf</filename>'
<literal>hosts:</literal> line (but after the <literal>files</literal> or <literal>mymachines</literal> entries),
replacing the <literal>dns</literal> entry if it exists, to ensure DNS queries are always routed via
<citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
<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>
<title>Example</title>
<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
shadow: compat
hosts: files mymachines <command>resolve</command> myhostname
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis</programlisting>
</refsect1>
<refsect1>
<title>See Also</title>
<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-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>