<?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+ --> <refentry id="nss-resolve" conditional='ENABLE_NSS_RESOLVE'> <refentryinfo> <title>nss-resolve</title> <productname>systemd</productname> </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>. 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> 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>nss-resolve</command> correctly:</para> <!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf --> <programlisting>passwd: compat mymachines systemd group: compat mymachines systemd shadow: compat hosts: files mymachines <command>resolve [!UNAVAIL=return]</command> dns 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-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> </refentry>