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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>systemd.link</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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</style><a href="index.html">Index </a>·
<a href="systemd.directives.html">Directives </a>·
<a href="../python-systemd/index.html">Python </a>·
<a href="../libudev/index.html">libudev </a>·
<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</span><hr><div class="refentry"><a name="systemd.link"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd.link — Network device configuration</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename"><em class="replaceable"><code>link</code></em>.link</code></p></div><div class="refsect1"><a name="idm140728386062000"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description"></a></h2><p>Network link configuration is performed by the
<span class="command"><strong>net_setup_link</strong></span> udev builtin.</p><p>The link files are read from the files located in the system
network directory <code class="filename">/usr/lib/systemd/network</code>,
the volatile runtime network directory
<code class="filename">/run/systemd/network</code>, and the local
administration network directory
<code class="filename">/etc/systemd/network</code>. Link files must have
the extension <code class="filename">.link</code>; other extensions are
ignored. All link 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 <code class="filename">/etc</code> have the highest priority, files in
<code class="filename">/run</code> take precedence over files with the same
name in <code class="filename">/usr/lib</code>. This can be used to
override a system-supplied link file with a local file if needed;
a symlink in <code class="filename">/etc</code> with the same name as a
link file in <code class="filename">/usr/lib</code>, pointing to
<code class="filename">/dev/null</code>, disables the link file
entirely.</p><p>The link file contains a "<code class="literal">[Match]</code>" section,
which determines if a given link file may be applied to a given
device, as well as a "<code class="literal">[Link]</code>" section specifying
how the device should be configured. The first (in lexical order)
of the link files that matches a given device is applied. Note
that a default file <code class="filename">99-default.link</code> is
shipped by the system, any user-supplied
<code class="filename">.link</code> should hence have a lexically earlier
name to be considered at all.</p></div><div class="refsect1"><a name="idm140728386049088"></a><h2 id="[Match] Section Options">[Match] Section Options<a class="headerlink" title="Permalink to this headline" href="#%5BMatch%5D%20Section%20Options"></a></h2><p>A link file is said to match a device if each of the entries
in the "<code class="literal">[Match]</code>" section matches, or if the
section is empty. The following keys are accepted:</p><div class="variablelist"><dl class="variablelist"><dt id="MACAddress="><span class="term"><code class="varname">MACAddress=</code></span><a class="headerlink" title="Permalink to this term" href="#MACAddress="></a></dt><dd><p>The hardware address.</p></dd><dt id="OriginalName="><span class="term"><code class="varname">OriginalName=</code></span><a class="headerlink" title="Permalink to this term" href="#OriginalName="></a></dt><dd><p>A whitespace-separated list of shell-style globs matching
the device name, as exposed by the udev property
"INTERFACE". This can not be used to match on names that have
already been changed from userspace. Caution is advised when matching on
kernel-assigned names, as they are known to be unstable
between reboots.</p></dd><dt id="Path="><span class="term"><code class="varname">Path=</code></span><a class="headerlink" title="Permalink to this term" href="#Path="></a></dt><dd><p>A whitespace-separated list of shell-style globs matching
the persistent path, as exposed by the udev property
"<code class="literal">ID_PATH</code>".</p></dd><dt id="Driver="><span class="term"><code class="varname">Driver=</code></span><a class="headerlink" title="Permalink to this term" href="#Driver="></a></dt><dd><p>A whitespace-separated list of shell-style globs matching
the driver currently bound to the device,
as exposed by the udev property "<code class="literal">DRIVER</code>"
of its parent device, or if that is not set, the
driver as exposed by "<code class="literal">ethtool -i</code>"
of the device itself.</p></dd><dt id="Type="><span class="term"><code class="varname">Type=</code></span><a class="headerlink" title="Permalink to this term" href="#Type="></a></dt><dd><p>A whitespace-separated list of shell-style globs matching
the device type, as exposed by the udev
property "<code class="literal">DEVTYPE</code>".</p></dd><dt id="Host="><span class="term"><code class="varname">Host=</code></span><a class="headerlink" title="Permalink to this term" href="#Host="></a></dt><dd><p>Matches against the hostname or machine
ID of the host. See "<code class="literal">ConditionHost=</code>" in
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>
for details.</p></dd><dt id="Virtualization="><span class="term"><code class="varname">Virtualization=</code></span><a class="headerlink" title="Permalink to this term" href="#Virtualization="></a></dt><dd><p>Checks whether the system is executed in
a virtualized environment and optionally test
whether it is a specific implementation. See
"<code class="literal">ConditionVirtualization=</code>" in
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>
for details.</p></dd><dt id="KernelCommandLine="><span class="term"><code class="varname">KernelCommandLine=</code></span><a class="headerlink" title="Permalink to this term" href="#KernelCommandLine="></a></dt><dd><p>Checks whether a specific kernel command line option
is set (or if prefixed with the exclamation mark unset). See
"<code class="literal">ConditionKernelCommandLine=</code>" in
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>
for details.</p></dd><dt id="Architecture="><span class="term"><code class="varname">Architecture=</code></span><a class="headerlink" title="Permalink to this term" href="#Architecture="></a></dt><dd><p>Checks whether the system is running on a specific
architecture. See "<code class="literal">ConditionArchitecture=</code>"
in
<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>
for details.</p></dd></dl></div></div><div class="refsect1"><a name="idm140728389912768"></a><h2 id="[Link] Section Options">[Link] Section Options<a class="headerlink" title="Permalink to this headline" href="#%5BLink%5D%20Section%20Options"></a></h2><p>The "<code class="literal">[Link]</code>" section accepts the following
keys:</p><div class="variablelist"><dl class="variablelist"><dt id="Description="><span class="term"><code class="varname">Description=</code></span><a class="headerlink" title="Permalink to this term" href="#Description="></a></dt><dd><p>A description of the device.</p></dd><dt id="Alias="><span class="term"><code class="varname">Alias=</code></span><a class="headerlink" title="Permalink to this term" href="#Alias="></a></dt><dd><p>The "<code class="literal">ifalias</code>" is set to this
value.</p></dd><dt id="MACAddressPolicy="><span class="term"><code class="varname">MACAddressPolicy=</code></span><a class="headerlink" title="Permalink to this term" href="#MACAddressPolicy="></a></dt><dd><p>The policy by which the MAC address should be set. The
available policies are:
</p><div class="variablelist"><dl class="variablelist"><dt id="persistent"><span class="term">"<code class="literal">persistent</code>"</span><a class="headerlink" title="Permalink to this term" href="#persistent"></a></dt><dd><p>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.</p></dd><dt id="random"><span class="term">"<code class="literal">random</code>"</span><a class="headerlink" title="Permalink to this term" href="#random"></a></dt><dd><p>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.</p></dd></dl></div></dd><dt id="MACAddress="><span class="term"><code class="varname">MACAddress=</code></span><a class="headerlink" title="Permalink to this term" href="#MACAddress="></a></dt><dd><p>The MAC address to use, if no
"<code class="literal">MACAddressPolicy=</code>"
is specified.</p></dd><dt id="NamePolicy="><span class="term"><code class="varname">NamePolicy=</code></span><a class="headerlink" title="Permalink to this term" href="#NamePolicy="></a></dt><dd><p>An ordered, space-separated list of policies by which
the interface name should be set.
"<code class="literal">NamePolicy</code>" may be disabled by specifying
"<code class="literal">net.ifnames=0</code>" 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 "<code class="literal">ID_NET_NAME</code>", which
is, by default, used by a udev rule to set
"<code class="literal">NAME</code>". If the name has already been set by
userspace, no renaming is performed. The available policies
are:</p><div class="variablelist"><dl class="variablelist"><dt id="kernel"><span class="term">"<code class="literal">kernel</code>"</span><a class="headerlink" title="Permalink to this term" href="#kernel"></a></dt><dd><p>If the kernel claims that the name it has set
for a device is predictable, then no renaming is
performed.</p></dd><dt id="database"><span class="term">"<code class="literal">database</code>"</span><a class="headerlink" title="Permalink to this term" href="#database"></a></dt><dd><p>The name is set based on entries in the udev's
Hardware Database with the key
"<code class="literal">ID_NET_NAME_FROM_DATABASE</code>".
</p></dd><dt id="onboard"><span class="term">"<code class="literal">onboard</code>"</span><a class="headerlink" title="Permalink to this term" href="#onboard"></a></dt><dd><p>The name is set based on information given by
the firmware for on-board devices, as exported by the
udev property "<code class="literal">ID_NET_NAME_ONBOARD</code>".
</p></dd><dt id="slot"><span class="term">"<code class="literal">slot</code>"</span><a class="headerlink" title="Permalink to this term" href="#slot"></a></dt><dd><p>The name is set based on information given by
the firmware for hot-plug devices, as exported by the
udev property "<code class="literal">ID_NET_NAME_SLOT</code>".
</p></dd><dt id="path"><span class="term">"<code class="literal">path</code>"</span><a class="headerlink" title="Permalink to this term" href="#path"></a></dt><dd><p>The name is set based on the device's physical
location, as exported by the udev property
"<code class="literal">ID_NET_NAME_PATH</code>".</p></dd><dt id="mac"><span class="term">"<code class="literal">mac</code>"</span><a class="headerlink" title="Permalink to this term" href="#mac"></a></dt><dd><p>The name is set based on the device's persistent
MAC address, as exported by the udev property
"<code class="literal">ID_NET_NAME_MAC</code>".</p></dd></dl></div></dd><dt id="Name="><span class="term"><code class="varname">Name=</code></span><a class="headerlink" title="Permalink to this term" href="#Name="></a></dt><dd><p>The interface name to use in case all the
policies specified in
<code class="varname">NamePolicy=</code> fail, or in case
<code class="varname">NamePolicy=</code> is missing or
disabled.</p></dd><dt id="MTUBytes="><span class="term"><code class="varname">MTUBytes=</code></span><a class="headerlink" title="Permalink to this term" href="#MTUBytes="></a></dt><dd><p>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.</p></dd><dt id="BitsPerSecond="><span class="term"><code class="varname">BitsPerSecond=</code></span><a class="headerlink" title="Permalink to this term" href="#BitsPerSecond="></a></dt><dd><p>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.</p></dd><dt id="Duplex="><span class="term"><code class="varname">Duplex=</code></span><a class="headerlink" title="Permalink to this term" href="#Duplex="></a></dt><dd><p>The duplex mode to set for the device. The accepted
values are "<code class="literal">half</code>" and
"<code class="literal">full</code>".</p></dd><dt id="WakeOnLan="><span class="term"><code class="varname">WakeOnLan=</code></span><a class="headerlink" title="Permalink to this term" href="#WakeOnLan="></a></dt><dd><p>The Wake-on-LAN policy to set for the device. The
supported values are:</p><div class="variablelist"><dl class="variablelist"><dt id="phy"><span class="term">"<code class="literal">phy</code>"</span><a class="headerlink" title="Permalink to this term" href="#phy"></a></dt><dd><p>Wake on PHY activity.</p></dd><dt id="magic"><span class="term">"<code class="literal">magic</code>"</span><a class="headerlink" title="Permalink to this term" href="#magic"></a></dt><dd><p>Wake on receipt of a magic packet.
</p></dd><dt id="off"><span class="term">"<code class="literal">off</code>"</span><a class="headerlink" title="Permalink to this term" href="#off"></a></dt><dd><p>Never wake.</p></dd></dl></div></dd></dl></div></div><div class="refsect1"><a name="idm140728384948432"></a><h2 id="Example">Example<a class="headerlink" title="Permalink to this headline" href="#Example"></a></h2><div class="example"><a name="idm140728384947792"></a><p class="title"><b>Example 1. /etc/systemd/network/wireless.link</b></p><div class="example-contents"><pre class="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</pre></div></div><br class="example-break"></div><div class="refsect1"><a name="idm140728384946016"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also"></a></h2><p>
<a href="systemd-udevd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd-udevd.service</span>(8)</span></a>,
<a href="udevadm.html"><span class="citerefentry"><span class="refentrytitle">udevadm</span>(8)</span></a>,
<a href="systemd.netdev.html"><span class="citerefentry"><span class="refentrytitle">systemd.netdev</span>(5)</span></a>,
<a href="systemd.network.html"><span class="citerefentry"><span class="refentrytitle">systemd.network</span>(5)</span></a>
</p></div></div></body></html>
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