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<refentry id="systemd-networkd.service" conditional='ENABLE_NETWORKD'>

<refentryinfo>

<title>systemd-networkd.service</title>

<productname>systemd</productname>

<authorgroup>

<author>

<contrib>Developer</contrib>

<firstname>Tom</firstname>

<surname>Gundersen</surname>

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

</author>

</authorgroup>

</refentryinfo>

<refmeta>

<refentrytitle>systemd-networkd.service</refentrytitle>

<manvolnum>8</manvolnum>

</refmeta>

<refnamediv>

<refname>systemd-networkd.service</refname>

<refname>systemd-networkd</refname>

<refpurpose>Network manager</refpurpose>

</refnamediv>

<refsynopsisdiv>

<para><filename>systemd-networkd.service</filename></para>

<para><filename>/usr/lib/systemd/systemd-networkd</filename></para>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para><command>systemd-networkd</command> is a system

service that manages networks. It detects and configures

network devices as they appear, as well as creating virtual

network devices.</para>

<para>Network configurations applied before networkd is started

are not removed, and configuration applied by networkd are not

removed when networkd exits. This ensures restarting networkd

does not cut the network connection, and, in particular, that

it is safe to transition between the initrd and the real root,

and back.</para>

</refsect1>

<refsect1><title>Configuration Files</title>

<para>The configuration files are read from the files located in the

system network directory <filename>/usr/lib/systemd/network</filename>,

the volatile runtime network directory

<filename>/run/systemd/network</filename> and the local administration

network directory <filename>/etc/systemd/network</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; a symlink in

<filename>/etc</filename> with the same name as a configuration file in

<filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,

disables the configuration file entirely.</para>

<refsect2><title>Virtual Network Devices</title>

<para>Virtual Network Device files must have the extension

<filename>.netdev</filename>; other extensions are ignored. Virtual

network devices are created as soon as networkd is started.</para>

<para>The <literal>[NetDev]</literal> section accepts the following

keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Name</varname></term>

<listitem>

<para>The interface name used when creating the

bridge. This option is compulsory.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Kind</varname></term>

<listitem>

<para>The netdev kind. Currently, 'bridge', 'bond' and 'vlan'

are supported. This option is compulsory.</para>

</listitem>

</varlistentry>

</variablelist>

<para>The <literal>[VLAN]</literal> section only applies for netdevs of kind 'vlan',

and accepts the following keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Id</varname></term>

<listitem>

<para>The VLAN ID to use. An integer in the range 0–4094.

This option is compulsory.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

<refsect2><title>Networks</title>

<para>Network files must have the extension <filename>.network</filename>;

other extensions are ignored. Networks are applied to links whenever the links

appear.</para>

<para>The network file contains a <literal>[Match]</literal> section,

which determines if a given network file may be applied to a given device;

and a <literal>[Network]</literal> section specifying how the device should

be configured. The first (in lexical order) of the network files that

matches a given device is applied.</para>

<para>A network file is said to match a device if each of the entries in the

<literal>[Match]</literal> section matches, or if the section is empty.

The following keys are accepted:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>MACAddress</varname></term>

<listitem>

<para>The hardware address.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Path</varname></term>

<listitem>

<para>The persistent path, as exposed by the udev

property <literal>ID_PATH</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Driver</varname></term>

<listitem>

<para>The driver currently bound to the device, as

exposed by the udev property <literal>DRIVER</literal>.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Type</varname></term>

<listitem>

<para>The device type, as exposed by the udev property

<literal>DEVTYPE</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Name</varname></term>

<listitem>

<para>The device name, as exposed by the udev property

<literal>INTERFACE</literal>.</para>

</listitem>

</varlistentry>

</variablelist>

<para>The <literal>[Network]</literal> section accepts the following keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Description</varname></term>

<listitem>

<para>A description of the device. This is only used for

presentation purposes.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>DHCP</varname></term>

<listitem>

<para>A boolean. When true, enables basic DHCPv4 support.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Address</varname></term>

<listitem>

<para>A static IPv4 or IPv6 address and its prefix length,

separated by a '/' character. The format of the address must

be as described in

<citerefentry><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>

. This is a short-hand for an [Address] section only containing an Address key (see below).</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Gateway</varname></term>

<listitem>

<para>The gateway address, which must be in the format described in

<citerefentry><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>

. This is a short-hand for a [Route] section only containing a Gateway key.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>DNS</varname></term>

<listitem>

<para>A DNS server address, which must be in the format described in

<citerefentry><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>

.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Bridge</varname></term>

<listitem>

<para>The name of the bridge to add the link to.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Bond</varname></term>

<listitem>

<para>The name of the bond to add the link to.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>VLAN</varname></term>

<listitem>

<para>The name of a VLAN to create on the link. This option

may be specified more than once.</para>

</listitem>

</varlistentry>

</variablelist>

<para>The <literal>[Address]</literal> section accepts the following keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Address</varname></term>

<listitem>

<para>As in the <literal>[Network]</literal> section. This key is mandatory.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Label</varname></term>

<listitem>

<para>An address label.</para>

</listitem>

</varlistentry>

</variablelist>

<para>The <literal>[Route]</literal> section accepts the following keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Gateway</varname></term>

<listitem>

<para>As in the <literal>[Network]</literal> section. This key is mandatory.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Destination</varname></term>

<listitem>

<para>The destination prefix of the route. Possibly followed by a slash and the

prefixlength, if ommitted a full-length host route is assumed.</para>

</listitem>

</varlistentry>

</variablelist>

<para>The <literal>[DHCPv4]</literal> section accepts the following keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>UseDNS</varname></term>

<listitem>

<para>When true (the default), the DNS servers received from the DHCP server will

be used and take precedence over any statically configured ones.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseMTU</varname></term>

<listitem>

<para>When true, the interface maximum transmission unit from the DHCP server will

be used on the current link. Defaults to false.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseHostname</varname></term>

<listitem>

<para>When true (the default), the hostname received from the DHCP server

will be used as the transient hostname.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>CriticalConnection</varname></term>

<listitem>

<para>When true, the connection will never be torn down even if the DHCP lease

expires. This is contrary to the DHCP specification, but may be the best choice

if, say, the root filesystem relies on this connection. Defaults to false.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect2>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

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

<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,

</para>

</refsect1>

</refentry>