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2818N/A

2818N/A<refentry id="systemd.link">

2818N/A <refentryinfo>

2818N/A <title>systemd.link</title>

5227N/A <productname>systemd</productname>

2818N/A

2818N/A <authorgroup>

2818N/A <author>

2818N/A <contrib>Developer</contrib>

5227N/A <firstname>Tom</firstname>

2818N/A <surname>Gundersen</surname>

3869N/A </author>

2818N/A </authorgroup>

2818N/A </refentryinfo>

5227N/A

2899N/A <refmeta>

3817N/A <refentrytitle>systemd.link</refentrytitle>

3817N/A <manvolnum>5</manvolnum>

3817N/A </refmeta>

3817N/A

2818N/A <refnamediv>

2818N/A <refname>systemd.link</refname>

2818N/A <refpurpose>Network device configuration</refpurpose>

2818N/A </refnamediv>

2818N/A

2818N/A <refsynopsisdiv>

2818N/A <para><filename><replaceable>link</replaceable>.link</filename></para>

4976N/A </refsynopsisdiv>

2818N/A

2818N/A <refsect1>

2818N/A <title>Description</title>

2818N/A

2818N/A <para>Network link configuration is performed by the

2818N/A <command>net_setup_link</command> udev builtin.</para>

2818N/A

2818N/A <para>The link files are read from the files located in the system

2818N/A network directory <filename>/usr/lib/systemd/network</filename>,

2818N/A the volatile runtime network directory

2818N/A <filename>/run/systemd/network</filename>, and the local

2818N/A administration network directory

2818N/A <filename>/etc/systemd/network</filename>. Link files must have

2818N/A the extension <filename>.link</filename>; other extensions are

2818N/A ignored. All link files are collectively sorted and processed in

2818N/A lexical order, regardless of the directories in which they live.

2818N/A However, files with identical filenames replace each other. Files

2818N/A in <filename>/etc</filename> have the highest priority, files in

2818N/A <filename>/run</filename> take precedence over files with the same

2818N/A name in <filename>/usr/lib</filename>. This can be used to

2818N/A override a system-supplied link file with a local file if needed;

2818N/A a symlink in <filename>/etc</filename> with the same name as a

2818N/A link file in <filename>/usr/lib</filename>, pointing to

2818N/A <filename>/dev/null</filename>, disables the link file

2818N/A entirely.</para>

2818N/A

4302N/A <para>The link file contains a <literal>[Match]</literal> section,

4302N/A which determines if a given link file may be applied to a given

5934N/A device, as well as a <literal>[Link]</literal> section specifying

5934N/A how the device should be configured. The first (in lexical order)

5934N/A of the link files that matches a given device is applied. Note

5934N/A that a default file <filename>99-default.link</filename> is

4302N/A shipped by the system, any user-supplied

4302N/A <filename>.link</filename> should hence have a lexically earlier

3633N/A name to be considered at all.</para>

3633N/A </refsect1>

3633N/A

2818N/A <refsect1>

2818N/A <title>[Match] Section Options</title>

2818N/A

2818N/A <para>A link file is said to match a device if each of the entries

2818N/A in the <literal>[Match]</literal> section matches, or if the

2818N/A section is empty. The following keys are accepted:</para>

2818N/A

2818N/A <variablelist class='network-directives'>

2818N/A <varlistentry>

2818N/A <term><varname>MACAddress=</varname></term>

2818N/A <listitem>

2818N/A <para>The hardware address.</para>

2818N/A </listitem>

2818N/A </varlistentry>

2818N/A <varlistentry>

3693N/A <term><varname>OriginalName=</varname></term>

3693N/A <listitem>

3693N/A <para>A whitespace-separated list of shell-style globs matching

3693N/A the device name, as exposed by the udev property

3693N/A "INTERFACE". This can not be used to match on names that have

3693N/A already been changed from userspace. Caution is advised when matching on

3693N/A kernel-assigned names, as they are known to be unstable

2818N/A between reboots.</para>

2818N/A </listitem>

2818N/A </varlistentry>

2818N/A <varlistentry>

2818N/A <term><varname>Path=</varname></term>

2818N/A <listitem>

2818N/A <para>A whitespace-separated list of shell-style globs matching

2818N/A the persistent path, as exposed by the udev property

3251N/A <literal>ID_PATH</literal>.</para>

2818N/A </listitem>

2818N/A </varlistentry>

2818N/A <varlistentry>

2818N/A <term><varname>Driver=</varname></term>

2818N/A <listitem>

2818N/A <para>A whitespace-separated list of shell-style globs matching

2818N/A the driver currently bound to the device,

2818N/A as exposed by the udev property <literal>DRIVER</literal>

3693N/A of its parent device, or if that is not set, the

2818N/A driver as exposed by <literal>ethtool -i</literal>

2818N/A of the device itself.</para>

2818N/A </listitem>

2818N/A </varlistentry>

2818N/A <varlistentry>

2818N/A <term><varname>Type=</varname></term>

2818N/A <listitem>

2818N/A <para>A whitespace-separated list of shell-style globs matching

2818N/A the device type, as exposed by the udev

2818N/A property <literal>DEVTYPE</literal>.</para>

3497N/A </listitem>

3497N/A </varlistentry>

3497N/A <varlistentry>

3497N/A <term><varname>Host=</varname></term>

3497N/A <listitem>

3497N/A <para>Matches against the hostname or machine

3497N/A ID of the host. See <literal>ConditionHost=</literal> in

3497N/A <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

3497N/A for details.</para>

3497N/A </listitem>

3497N/A </varlistentry>

3497N/A <varlistentry>

3497N/A <term><varname>Virtualization=</varname></term>

3497N/A <listitem>

3693N/A <para>Checks whether the system is executed in

3497N/A a virtualized environment and optionally test

3497N/A whether it is a specific implementation. See

4828N/A <literal>ConditionVirtualization=</literal> in

4828N/A <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

3497N/A for details.</para>

3497N/A </listitem>

3497N/A </varlistentry>

3497N/A <varlistentry>

4828N/A <term><varname>KernelCommandLine=</varname></term>

4828N/A <listitem>

3497N/A <para>Checks whether a specific kernel command line option

2818N/A is set (or if prefixed with the exclamation mark unset). See

3477N/A <literal>ConditionKernelCommandLine=</literal> in

2818N/A <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

2818N/A for details.</para>

2818N/A </listitem>

2818N/A </varlistentry>

2818N/A <varlistentry>

2818N/A <term><varname>Architecture=</varname></term>

2818N/A <listitem>

2818N/A <para>Checks whether the system is running on a specific

2818N/A architecture. See <literal>ConditionArchitecture=</literal>

2818N/A in

2818N/A <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

2818N/A for details.</para>

2818N/A </listitem>

3722N/A </varlistentry>

3722N/A </variablelist>

2818N/A

2818N/A </refsect1>

4089N/A

4089N/A <refsect1>

4089N/A <title>[Link] Section Options</title>

4089N/A

4089N/A <para>The <literal>[Link]</literal> section accepts the following

2818N/A keys:</para>

3747N/A

3747N/A <variablelist class='network-directives'>

3747N/A <varlistentry>

3747N/A <term><varname>Description=</varname></term>

3747N/A <listitem>

3747N/A <para>A description of the device.</para>

3747N/A </listitem>

2818N/A </varlistentry>

4089N/A <varlistentry>

2818N/A <term><varname>Alias=</varname></term>

3817N/A <listitem>

3817N/A <para>The <literal>ifalias</literal> is set to this

3817N/A value.</para>

3817N/A </listitem>

3817N/A </varlistentry>

3817N/A <varlistentry>

3817N/A <term><varname>MACAddressPolicy=</varname></term>

3817N/A <listitem>

3817N/A <para>The policy by which the MAC address should be set. The

3817N/A available policies are:

3817N/A </para>

3817N/A

3817N/A <variablelist>

3817N/A <varlistentry>

<term><literal>persistent</literal></term>

<listitem>

<para>If the hardware has a persistent MAC address, as

most hardware should, and if it is used by the kernel,

nothing is done. Otherwise, a new MAC address is

generated which is guaranteed to be the same on every

boot for the given machine and the given device, but

which is otherwise random. This feature depends on ID_NET_NAME_*

properties existing for the link, on hardware where these

properties are not set the generation of a persistent MAC address

will fail.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>random</literal></term>

<listitem>

<para>If the kernel is using a random MAC address,

nothing is done. Otherwise, a new address is randomly

generated each time the device appears, typically at

boot.</para>

</listitem>

</varlistentry>

</variablelist>

</listitem>

</varlistentry>

<varlistentry>

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

<listitem>

<para>The MAC address to use, if no

<literal>MACAddressPolicy=</literal>

is specified.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>NamePolicy=</varname></term>

<listitem>

<para>An ordered, space-separated list of policies by which

the interface name should be set.

<literal>NamePolicy</literal> may be disabled by specifying

<literal>net.ifnames=0</literal> on the kernel command line.

Each of the policies may fail, and the first successful one

is used. The name is not set directly, but is exported to

udev as the property <literal>ID_NET_NAME</literal>, which

is, by default, used by a udev rule to set

<literal>NAME</literal>. If the name has already been set by

userspace, no renaming is performed. The available policies

are:</para>

<variablelist>

<varlistentry>

<term><literal>kernel</literal></term>

<listitem>

<para>If the kernel claims that the name it has set

for a device is predictable, then no renaming is

performed.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>database</literal></term>

<listitem>

<para>The name is set based on entries in the udev's

Hardware Database with the key

<literal>ID_NET_NAME_FROM_DATABASE</literal>.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>onboard</literal></term>

<listitem>

<para>The name is set based on information given by

the firmware for on-board devices, as exported by the

udev property <literal>ID_NET_NAME_ONBOARD</literal>.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>slot</literal></term>

<listitem>

<para>The name is set based on information given by

the firmware for hot-plug devices, as exported by the

udev property <literal>ID_NET_NAME_SLOT</literal>.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>path</literal></term>

<listitem>

<para>The name is set based on the device's physical

location, as exported by the udev property

<literal>ID_NET_NAME_PATH</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>mac</literal></term>

<listitem>

<para>The name is set based on the device's persistent

MAC address, as exported by the udev property

<literal>ID_NET_NAME_MAC</literal>.</para>

</listitem>

</varlistentry>

</variablelist>

</listitem>

</varlistentry>

<varlistentry>

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

<listitem>

<para>The interface name to use in case all the

policies specified in

<varname>NamePolicy=</varname> fail, or in case

<varname>NamePolicy=</varname> is missing or

disabled.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>MTUBytes=</varname></term>

<listitem>

<para>The maximum transmission unit in bytes to set for the

device. The usual suffixes K, M, G, are supported and are

understood to the base of 1024.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>BitsPerSecond=</varname></term>

<listitem>

<para>The speed to set for the device, the value is rounded

down to the nearest Mbps. The usual suffixes K, M, G, are

supported and are understood to the base of 1000.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Duplex=</varname></term>

<listitem>

<para>The duplex mode to set for the device. The accepted

values are <literal>half</literal> and

<literal>full</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>WakeOnLan=</varname></term>

<listitem>

<para>The Wake-on-LAN policy to set for the device. The

supported values are:</para>

<variablelist>

<varlistentry>

<term><literal>phy</literal></term>

<listitem>

<para>Wake on PHY activity.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>magic</literal></term>

<listitem>

<para>Wake on receipt of a magic packet.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><literal>off</literal></term>

<listitem>

<para>Never wake.</para>

</listitem>

</varlistentry>

</variablelist>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>Example</title>

<example>

<title>/etc/systemd/network/wireless.link</title>

<programlisting>[Match]

MACAddress=12:34:56:78:9a:bc

Driver=brcmsmac

Path=pci-0000:02:00.0-*

Type=wlan

Virtualization=no

Host=my-laptop

Architecture=x86-64

[Link]

Name=wireless0

MTUBytes=1450

BitsPerSecond=10M

WakeOnLan=magic

MACAddress=cb:a9:87:65:43:21</programlisting>

</example>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

<citerefentry>

<refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>

</citerefentry>,

<citerefentry>

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

</citerefentry>

</para>

</refsect1>

</refentry>