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112fd4f283bc07af680c305545d6e31dcde4b943gryzor

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112fd4f283bc07af680c305545d6e31dcde4b943gryzor<refentry id="systemd-resolved.service" conditional='ENABLE_RESOLVED'>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refentryinfo>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <title>systemd-resolved.service</title>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <productname>systemd</productname>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <authorgroup>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <author>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <contrib>Developer</contrib>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <firstname>Tom</firstname>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <surname>Gundersen</surname>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <email>teg@jklm.no</email>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor </author>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor </authorgroup>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor </refentryinfo>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refmeta>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refentrytitle>systemd-resolved.service</refentrytitle>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <manvolnum>8</manvolnum>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor </refmeta>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refnamediv>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refname>systemd-resolved.service</refname>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refname>systemd-resolved</refname>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refpurpose>Network Name Resolution manager</refpurpose>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor </refnamediv>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refsynopsisdiv>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <para><filename>systemd-resolved.service</filename></para>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <para><filename>/usr/lib/systemd/systemd-resolved</filename></para>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor </refsynopsisdiv>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <refsect1>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <title>Description</title>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <para><command>systemd-resolved</command> is a system service that provides network name resolution to local

112fd4f283bc07af680c305545d6e31dcde4b943gryzor applications. It implements a caching and validating DNS/DNSSEC stub resolver, as well as an LLMNR resolver and

112fd4f283bc07af680c305545d6e31dcde4b943gryzor responder. In addition it maintains the <filename>/run/systemd/resolve/resolv.conf</filename> file for

112fd4f283bc07af680c305545d6e31dcde4b943gryzor compatibility with traditional Linux programs. This file may be symlinked from

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <filename>/etc/resolv.conf</filename>.</para>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <para>The glibc NSS module

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry> is required to

112fd4f283bc07af680c305545d6e31dcde4b943gryzor permit glibc's NSS resolver functions to resolve host names via <command>systemd-resolved</command>.</para>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <para>The DNS servers contacted are determined from the global

112fd4f283bc07af680c305545d6e31dcde4b943gryzor settings in <filename>/etc/systemd/resolved.conf</filename>, the

112fd4f283bc07af680c305545d6e31dcde4b943gryzor per-link static settings in <filename>/etc/systemd/network/*.network</filename> files,

112fd4f283bc07af680c305545d6e31dcde4b943gryzor and the per-link dynamic settings received over DHCP. See

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor and

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor for details. To improve compatibility,

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <filename>/etc/resolv.conf</filename> is read in order to discover

112fd4f283bc07af680c305545d6e31dcde4b943gryzor configured system DNS servers, but only if it is not a symlink

112fd4f283bc07af680c305545d6e31dcde4b943gryzor to <filename>/run/systemd/resolve/resolv.conf</filename> (see above).</para>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <para><command>systemd-resolved</command> synthesizes DNS RRs for the following cases:</para>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <itemizedlist>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <listitem><para>The local, configured hostname is resolved to

112fd4f283bc07af680c305545d6e31dcde4b943gryzor all locally configured IP addresses ordered by their scope, or

112fd4f283bc07af680c305545d6e31dcde4b943gryzor — if none are configured — the IPv4 address 127.0.0.2 (which

112fd4f283bc07af680c305545d6e31dcde4b943gryzor is on the local loopback) and the IPv6 address ::1 (which is the

112fd4f283bc07af680c305545d6e31dcde4b943gryzor local host).</para></listitem>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <listitem><para>The hostname <literal>localhost</literal> (as well as any hostname ending in

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <literal>.localhost</literal>, <literal>.localdomain</literal> or equal to <literal>localdomain</literal>) is

112fd4f283bc07af680c305545d6e31dcde4b943gryzor resolved to the IP addresses 127.0.0.1 and ::1.</para></listitem>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <listitem><para>The hostname <literal>gateway</literal> is

112fd4f283bc07af680c305545d6e31dcde4b943gryzor resolved to all current default routing gateway addresses,

112fd4f283bc07af680c305545d6e31dcde4b943gryzor ordered by their metric. This assigns a stable hostname to the

112fd4f283bc07af680c305545d6e31dcde4b943gryzor current gateway, useful for referencing it independently of the

112fd4f283bc07af680c305545d6e31dcde4b943gryzor current network configuration state.</para></listitem>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <listitem><para>The mappings defined in <filename>/etc/hosts</filename> are resolved to their configured

112fd4f283bc07af680c305545d6e31dcde4b943gryzor addresses and back.</para></listitem>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor </itemizedlist>

112fd4f283bc07af680c305545d6e31dcde4b943gryzor

112fd4f283bc07af680c305545d6e31dcde4b943gryzor <para>Lookup requests are routed to the available DNS servers

112fd4f283bc07af680c305545d6e31dcde4b943gryzor and LLMNR interfaces according to the following rules:</para>

<itemizedlist>

<listitem><para>Lookups for the special hostname

<literal>localhost</literal> are never routed to the

network. (A few other, special domains are handled the same way.)</para></listitem>

<listitem><para>Single-label names are routed to all local

interfaces capable of IP multicasting, using the LLMNR

protocol. Lookups for IPv4 addresses are only sent via LLMNR on

IPv4, and lookups for IPv6 addresses are only sent via LLMNR on

IPv6. Lookups for the locally configured host name and the

<literal>gateway</literal> host name are never routed to

LLMNR.</para></listitem>

<listitem><para>Multi-label names are routed to all local

interfaces that have a DNS sever configured, plus the globally

configured DNS server if there is one. Address lookups from the

link-local address range are never routed to

DNS.</para></listitem>

</itemizedlist>

<para>If lookups are routed to multiple interfaces, the first

successful response is returned (thus effectively merging the

lookup zones on all matching interfaces). If the lookup failed on

all interfaces, the last failing response is returned.</para>

<para>Routing of lookups may be influenced by configuring

per-interface domain names. See

<citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for details. Lookups for a hostname ending in one of the

per-interface domains are exclusively routed to the matching

interfaces.</para>

<para>Note that <filename>/run/systemd/resolve/resolv.conf</filename> should not be used directly by applications,

but only through a symlink from <filename>/etc/resolv.conf</filename>.</para>

<para>See the <ulink url="http://www.freedesktop.org/wiki/Software/systemd/resolved"> resolved D-Bus API

Documentation</ulink> for information about the APIs <filename>systemd-resolved</filename> provides.</para>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

<citerefentry><refentrytitle>dnssec-trust-anchors.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

<citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd-resolve</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

<citerefentry project='man-pages'><refentrytitle>hosts</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>