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d296c20f1f
I am pretty sure /etc/hosts (i.e. an explicitly configured, local, trusted database) should be useful for overriding the automatic myhostname logic. resolved's internal logic handles it that way and hence we should suggest it in the NSS fallback line, too. Let's also bring the factory file back into sync with what the docs say. And update the prose a bit too, to actually match what we recommend.
92 lines
4.2 KiB
XML
92 lines
4.2 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="nss-resolve" conditional='ENABLE_NSS_RESOLVE'>
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<refentryinfo>
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<title>nss-resolve</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>nss-resolve</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>nss-resolve</refname>
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<refname>libnss_resolve.so.2</refname>
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<refpurpose>Hostname resolution via <filename>systemd-resolved.service</filename></refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>libnss_resolve.so.2</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>nss-resolve</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of the
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GNU C Library (<command>glibc</command>) enabling it to resolve hostnames via the
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<citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry> local network
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name resolution service. It replaces the <command>nss-dns</command> plug-in module that traditionally resolves
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hostnames via DNS.</para>
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<para>To activate the NSS module, add <literal>resolve [!UNAVAIL=return]</literal> to the line starting
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with <literal>hosts:</literal> in <filename>/etc/nsswitch.conf</filename>. Specifically, it is
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recommended to place <literal>resolve</literal> early in <filename>/etc/nsswitch.conf</filename>'s
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<literal>hosts:</literal> line. It should be before the <literal>files</literal> entry, since
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<filename>systemd-resolved</filename> supports <filename>/etc/hosts</filename> internally, but with
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caching. To the contrary, it should be after <literal>mymachines</literal>, to give hostnames given to
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local VMs and containers precedence over names received over DNS. Finally, we recommend placing
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<literal>dns</literal> somewhere after <literal>resolve</literal>, to fall back to
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<command>nss-dns</command> if <filename>systemd-resolved.service</filename> is not available.</para>
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<para>Note that <command>systemd-resolved</command> will synthesize DNS resource records in a few cases,
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for example for <literal>localhost</literal> and the current local hostname, see
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<citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry> for
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the full list. This duplicates the functionality of
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<citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>, but
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it is still recommended (see examples below) to keep <command>nss-myhostname</command> configured in
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<filename>/etc/nsswitch.conf</filename>, to keep those names resolveable if
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<command>systemd-resolved</command> is not running.</para>
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</refsect1>
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<refsect1>
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<title>Example</title>
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<para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables <command>nss-resolve</command>
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correctly:</para>
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<!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
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<programlisting>passwd: compat systemd
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group: compat [SUCCESS=merge] systemd
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shadow: compat
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hosts: mymachines <command>resolve [!UNAVAIL=return]</command> files myhostname dns
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networks: files
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protocols: db files
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services: db files
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ethers: db files
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rpc: db files
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netgroup: nis</programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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