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+<?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-or-later -->
+
+<refentry id="systemd.dnssd"
+ xmlns:xi="http://www.w3.org/2001/XInclude"
+ conditional='ENABLE_RESOLVE'>
+
+ <refentryinfo>
+ <title>systemd.dnssd</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>systemd.dnssd</refentrytitle>
+ <manvolnum>5</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>systemd.dnssd</refname>
+ <refpurpose>DNS-SD configuration</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename><replaceable>network_service</replaceable>.dnssd</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>DNS-SD setup is performed by
+ <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+ </para>
+
+ <para>The main network service file must have the extension <filename>.dnssd</filename>; other
+ extensions are ignored.</para>
+
+ <para>The <filename>.dnssd</filename> files are read from the files located in the system network
+ directories <filename>/usr/lib/systemd/dnssd</filename> and
+ <filename>/usr/local/lib/systemd/dnssd</filename>, the volatile runtime network directory
+ <filename>/run/systemd/dnssd</filename> and the local administration network directory
+ <filename>/etc/systemd/dnssd</filename>. All configuration files are collectively sorted and processed in
+ lexical order, regardless of the directories in which they live. However, files with identical filenames
+ replace each other. Files in <filename>/etc/</filename> have the highest priority, files in
+ <filename>/run/</filename> take precedence over files with the same name in
+ <filename>/usr/lib/</filename>. This can be used to override a system-supplied configuration file with a
+ local file if needed.</para>
+
+ <para>Along with the network service file <filename>foo.dnssd</filename>, a "drop-in" directory
+ <filename>foo.dnssd.d/</filename> may exist. All files with the suffix
+ <literal>.conf</literal> from this directory will be parsed after the file itself is
+ parsed. This is useful to alter or add configuration settings, without having to modify the main
+ configuration file. Each drop-in file must have appropriate section headers.</para>
+
+ <para>In addition to <filename>/etc/systemd/dnssd</filename>, drop-in <literal>.d</literal> directories
+ can be placed in <filename>/usr/lib/systemd/dnssd</filename> or <filename>/run/systemd/dnssd</filename>
+ directories. Drop-in files in <filename>/etc/</filename> take precedence over those in
+ <filename>/run/</filename> which in turn take precedence over those in <filename>/usr/lib/</filename> or
+ <filename>/usr/local/lib</filename>. Drop-in files under any of these directories take precedence over
+ the main network service file wherever located.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>[Service] Section Options</title>
+
+ <para>The network service file contains a [Service]
+ section, which specifies a discoverable network service announced in a
+ local network with Multicast DNS broadcasts.</para>
+
+ <variablelist class='network-directives'>
+ <varlistentry>
+ <term><varname>Name=</varname></term>
+ <listitem>
+ <para>An instance name of the network service as defined in the section 4.1.1 of <ulink
+ url="https://tools.ietf.org/html/rfc6763">RFC 6763</ulink>, e.g. <literal>webserver</literal>.</para>
+ <para>The option supports simple specifier expansion. The following expansions are understood:</para>
+ <table class='specifiers'>
+ <title>Specifiers available</title>
+ <tgroup cols='3' align='left' colsep='1' rowsep='1'>
+ <colspec colname="spec" />
+ <colspec colname="mean" />
+ <colspec colname="detail" />
+ <thead>
+ <row>
+ <entry>Specifier</entry>
+ <entry>Meaning</entry>
+ <entry>Details</entry>
+ </row>
+ </thead>
+ <tbody>
+ <xi:include href="standard-specifiers.xml" xpointer="a"/>
+ <xi:include href="standard-specifiers.xml" xpointer="A"/>
+ <xi:include href="standard-specifiers.xml" xpointer="b"/>
+ <xi:include href="standard-specifiers.xml" xpointer="B"/>
+ <xi:include href="standard-specifiers.xml" xpointer="H"/>
+ <xi:include href="standard-specifiers.xml" xpointer="m"/>
+ <xi:include href="standard-specifiers.xml" xpointer="M"/>
+ <xi:include href="standard-specifiers.xml" xpointer="o"/>
+ <xi:include href="standard-specifiers.xml" xpointer="v"/>
+ <xi:include href="standard-specifiers.xml" xpointer="w"/>
+ <xi:include href="standard-specifiers.xml" xpointer="W"/>
+ <xi:include href="standard-specifiers.xml" xpointer="percent"/>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <xi:include href="version-info.xml" xpointer="v236"/>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>Type=</varname></term>
+ <listitem>
+ <para>A type of the network service as defined in the section 4.1.2 of <ulink
+ url="https://tools.ietf.org/html/rfc6763">RFC 6763</ulink>, e.g. <literal>_http._tcp</literal>.
+ </para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>Port=</varname></term>
+ <listitem>
+ <para>An IP port number of the network service.</para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>Priority=</varname></term>
+ <listitem>
+ <para>A priority number set in <constant class='dns'>SRV</constant> resource records corresponding
+ to the network service.</para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>Weight=</varname></term>
+ <listitem>
+ <para>A weight number set in <constant class='dns'>SRV</constant> resource records corresponding
+ to the network service.</para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>TxtText=</varname></term>
+ <listitem>
+ <para>A whitespace-separated list of arbitrary key/value pairs
+ conveying additional information about the named service in the corresponding TXT resource record,
+ e.g. <literal>path=/portal/index.html</literal>. Keys and values can contain C-style escape
+ sequences which get translated upon reading configuration files.
+ </para>
+ <para>This option together with <varname>TxtData=</varname> may be specified more than once, in which
+ case multiple TXT resource records will be created for the service. If the empty string is assigned to
+ this option, the list is reset and all prior assignments will have no effect.
+ </para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>TxtData=</varname></term>
+ <listitem>
+ <para>A whitespace-separated list of arbitrary key/value pairs
+ conveying additional information about the named service in the corresponding TXT resource record
+ where values are base64-encoded string representing any binary data,
+ e.g. <literal>data=YW55IGJpbmFyeSBkYXRhCg==</literal>. Keys can contain C-style escape
+ sequences which get translated upon reading configuration files.
+ </para>
+ <para>This option together with <varname>TxtText=</varname> may be specified more than once, in which
+ case multiple TXT resource records will be created for the service. If the empty string is assigned to
+ this option, the list is reset and all prior assignments will have no effect.
+ </para>
+
+ <xi:include href="version-info.xml" xpointer="v236"/>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+ <example>
+ <title>HTTP service</title>
+
+ <programlisting># /etc/systemd/dnssd/http.dnssd
+[Service]
+Name=%H
+Type=_http._tcp
+Port=80
+TxtText=path=/stats/index.html t=temperature_sensor</programlisting>
+
+ <para>This makes the http server running on the host discoverable in the local network
+ given MulticastDNS is enabled on the network interface.</para>
+
+ <para>Now the utility <literal>resolvectl</literal> should be able to resolve the
+ service to the host's name:</para>
+
+ <programlisting>$ resolvectl service meteo._http._tcp.local
+meteo._http._tcp.local: meteo.local:80 [priority=0, weight=0]
+ 169.254.208.106%senp0s21f0u2u4
+ fe80::213:3bff:fe49:8aa%senp0s21f0u2u4
+ path=/stats/index.html
+ t=temperature_sensor
+ (meteo/_http._tcp/local)
+
+-- Information acquired via protocol mDNS/IPv6 in 4.0ms.
+-- Data is authenticated: yes</programlisting>
+
+ <para><literal>Avahi</literal> running on a different host in the same local network should see the service as well:</para>
+
+ <programlisting>$ avahi-browse -a -r
++ enp3s0 IPv6 meteo Web Site local
++ enp3s0 IPv4 meteo Web Site local
+= enp3s0 IPv6 meteo Web Site local
+ hostname = [meteo.local]
+ address = [fe80::213:3bff:fe49:8aa]
+ port = [80]
+ txt = ["path=/stats/index.html" "t=temperature_sensor"]
+= enp3s0 IPv4 meteo Web Site local
+ hostname = [meteo.local]
+ address = [169.254.208.106]
+ port = [80]
+ txt = ["path=/stats/index.html" "t=temperature_sensor"]</programlisting>
+
+ </example>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>resolvectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>