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7 This file is part of systemd.
9 Copyright 2014 Tom Gundersen
11 systemd is free software; you can redistribute it and/or modify it
12 under the terms of the GNU Lesser General Public License as published by
13 the Free Software Foundation; either version 2.1 of the License, or
14 (at your option) any later version.
16 systemd is distributed in the hope that it will be useful, but
17 WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 Lesser General Public License for more details.
21 You should have received a copy of the GNU Lesser General Public License
22 along with systemd; If not, see <http://www.gnu.org/licenses/>.
25 <refentry id="systemd.link">
27 <title>systemd.link</title>
28 <productname>systemd</productname>
32 <contrib>Developer</contrib>
33 <firstname>Tom</firstname>
34 <surname>Gundersen</surname>
40 <refentrytitle>systemd.link</refentrytitle>
41 <manvolnum>5</manvolnum>
45 <refname>systemd.link</refname>
46 <refpurpose>Network device configuration</refpurpose>
50 <para><filename><replaceable>link</replaceable>.link</filename></para>
54 <title>Description</title>
56 <para>Network link configuration is performed by the <command>net_setup_link</command>
59 <para>The link files are read from the files located in the
60 system network directory <filename>/usr/lib/systemd/network</filename>,
61 the volatile runtime network directory <filename>/run/systemd/network</filename>,
62 and the local administration network directory <filename>/etc/systemd/network</filename>.
63 Link files must have the extension <filename>.link</filename>; other extensions are ignored.
64 All link files are collectively sorted and processed in lexical order,
65 regardless of the directories in which they live. However, files with
66 identical filenames replace each other. Files in <filename>/etc</filename>
67 have the highest priority, files in <filename>/run</filename> take precedence
68 over files with the same name in <filename>/usr/lib</filename>. This can be
69 used to override a system-supplied link file with a local file if needed;
70 a symlink in <filename>/etc</filename> with the same name as a link file in
71 <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
72 disables the link file entirely.</para>
74 <para>The link file contains a <literal>[Match]</literal> section, which
75 determines if a given link file may be applied to a given device; and a
76 <literal>[Link]</literal> section specifying how the device should be
77 configured. The first (in lexical order) of the link files that matches
78 a given device is applied.</para>
82 <title>[Match] Section Options</title>
84 <para>A link file is said to match a device if each of the entries in the
85 <literal>[Match]</literal> section matches, or if the section is empty.
86 The following keys are accepted:</para>
88 <variablelist class='network-directives'>
90 <term><varname>MACAddress=</varname></term>
92 <para>The hardware address.</para>
96 <term><varname>OriginalName=</varname></term>
98 <para>The device name, as exposed by the udev
99 property "INTERFACE". May contain shell style
100 globs. This can not be used to match on names
101 that have already been changed from userspace.
102 Caution is advised when matching on
103 kernel-assigned names, as they are known to
104 be unstable between reboots.</para>
108 <term><varname>Path=</varname></term>
110 <para>The persistent path, as exposed by the
111 udev property <literal>ID_PATH</literal>. May
112 contain shell style globs.</para>
116 <term><varname>Driver=</varname></term>
118 <para>The driver currently bound to the device,
119 as exposed by the udev property <literal>DRIVER</literal>
120 of its parent device, or if that is not set, the
121 driver as exposed by <literal>ethtool -i</literal>
122 of the device itself.</para>
126 <term><varname>Type=</varname></term>
128 <para>The device type, as exposed by the udev
129 property <literal>DEVTYPE</literal>.</para>
133 <term><varname>Host=</varname></term>
135 <para>Matches against the hostname or machine
136 ID of the host. See <literal>ConditionHost=</literal> in
137 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
142 <term><varname>Virtualization=</varname></term>
144 <para>Checks whether the system is executed in
145 a virtualized environment and optionally test
146 whether it is a specific implementation. See
147 <literal>ConditionVirtualization=</literal> in
148 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
153 <term><varname>KernelCommandLine=</varname></term>
155 <para>Checks whether a specific kernel command
156 line option is set (or if prefixed with the
157 exclamation mark unset). See
158 <literal>ConditionKernelCommandLine=</literal> in
159 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
164 <term><varname>Architecture=</varname></term>
166 <para>Checks whether the system is running on a
167 specific architecture. See
168 <literal>ConditionArchitecture=</literal> in
169 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
178 <title>[Link] Section Options</title>
180 <para>The <literal>[Link]</literal> section accepts the following
183 <variablelist class='network-directives'>
185 <term><varname>Description=</varname></term>
187 <para>A description of the device.</para>
191 <term><varname>Alias=</varname></term>
193 <para>The <literal>ifalias</literal> is set to
198 <term><varname>MACAddressPolicy=</varname></term>
200 <para>The policy by which the MAC address
201 should be set. The available policies are:
206 <term><literal>persistent</literal></term>
208 <para>If the hardware has a persistent
209 MAC address, as most hardware should,
210 and if it is used by the kernel, nothing
211 is done. Otherwise, a new MAC address
212 is generated which is guaranteed to be
213 the same on every boot for the given
214 machine and the given device, but which
215 is otherwise random.</para>
219 <term><literal>random</literal></term>
221 <para>If the kernel is using a random MAC
222 address, nothing is done. Otherwise, a new
223 address is randomly generated each time the
224 device appears, typically at boot.</para>
231 <term><varname>MACAddress=</varname></term>
233 <para>The MAC address to use, if no
234 <literal>MACAddressPolicy=</literal>
239 <term><varname>NamePolicy=</varname></term>
241 <para>An ordered, space-separated list of
242 policies by which the interface name should
243 be set. <literal>NamePolicy</literal> may be
244 disabled by specifying
245 <literal>net.ifnames=0</literal> on the kernel
246 command line. Each of the policies may fail, and
247 the first successful one is used. The name is
248 not set directly, but is exported to udev as
249 the property <literal>ID_NET_NAME</literal>,
250 which is, by default, used by a udev rule to set
251 <literal>NAME</literal>. If the name has already
252 been set by userspace, no renaming is performed.
253 The available policies are:</para>
257 <term><literal>kernel</literal></term>
259 <para>If the kernel claims that the name it
260 has set for a device is predictable, then
261 no renaming is performed.
266 <term><literal>database</literal></term>
268 <para>The name is set based on entries in
269 the udev's Hardware Database with the key
270 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
275 <term><literal>onboard</literal></term>
277 <para>The name is set based on information given by
278 the firmware for on-board devices, as exported by
279 the udev property <literal>ID_NET_NAME_ONBOARD</literal>.
284 <term><literal>slot</literal></term>
286 <para>The name is set based on information given by
287 the firmware for hot-plug devices, as exported by
288 the udev property <literal>ID_NET_NAME_SLOT</literal>.
293 <term><literal>path</literal></term>
295 <para>The name is set based on the device's physical
296 location, as exported by the udev property
297 <literal>ID_NET_NAME_PATH</literal>.</para>
301 <term><literal>mac</literal></term>
303 <para>The name is set based on the device's
304 persistent MAC address, as exported by the udev
305 property <literal>ID_NET_NAME_MAC</literal>.</para>
312 <term><varname>Name=</varname></term>
314 <para>The interface name to use in case all the
315 policies specified in
316 <varname>NamePolicy=</varname> fail, or in case
317 <varname>NamePolicy=</varname> is missing or
322 <term><varname>MTUBytes=</varname></term>
324 <para>The maximum transmission unit in bytes to
325 set for the device. The usual suffixes K, M, G,
326 are supported and are understood to the base of
331 <term><varname>BitsPerSecond=</varname></term>
333 <para>The speed to set for the device, the
334 value is rounded down to the nearest Mbps.
335 The usual suffixes K, M, G, are supported and
336 are understood to the base of 1000.</para>
340 <term><varname>Duplex=</varname></term>
342 <para>The duplex mode to set for the device.
343 The accepted values are <literal>half</literal>
344 and <literal>full</literal>.</para>
348 <term><varname>WakeOnLan=</varname></term>
350 <para>The Wake-on-LAN policy to set for the
351 device. The supported values are:</para>
355 <term><literal>phy</literal></term>
357 <para>Wake on PHY activity.</para>
361 <term><literal>magic</literal></term>
363 <para>Wake on receipt of a magic packet.
368 <term><literal>off</literal></term>
370 <para>Never wake.</para>
380 <title>Example</title>
382 <title>/etc/systemd/network/wireless.link</title>
384 <programlisting>[Match]
385 MACAddress=12:34:56:78:9a:bc
387 Path=pci-0000:02:00.0-*
398 MACAddress=cb:a9:87:65:43:21</programlisting>
403 <title>See Also</title>
406 <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
409 <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
412 <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
415 <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>