Adding upstream version 252.22.upstream/252.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1250 insertions, 0 deletions

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+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="systemd.link">
+  <refentryinfo>
+    <title>systemd.link</title>
+    <productname>systemd</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>systemd.link</refentrytitle>
+    <manvolnum>5</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>systemd.link</refname>
+    <refpurpose>Network device configuration</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <para><filename><replaceable>link</replaceable>.link</filename></para>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>A plain ini-style text file that encodes configuration for matching network devices, used by
+    <citerefentry><refentrytitle>systemd-udevd</refentrytitle><manvolnum>8</manvolnum></citerefentry> and in
+    particular its <command>net_setup_link</command> builtin. See
+    <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>7</manvolnum></citerefentry> for a
+    general description of the syntax.</para>
+
+    <para>The <filename>.link</filename> files are read from the files located in the system network
+    directory <filename>/usr/lib/systemd/network</filename> and
+    <filename>/usr/local/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 alphanumeric order, regardless of the directories in which they live. However, files
+    with identical filenames replace each other. It is recommended that each filename is prefixed with
+    a number (e.g. <filename>10-eth0.link</filename>). Otherwise, the default
+    <filename>.link</filename> files or those generated by
+    <citerefentry><refentrytitle>systemd-network-generator.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+    may take precedence over user configured files. 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 link file with a
+    local file if needed. As a special case, an empty file (file size 0) or symlink with the same name
+    pointing to <filename>/dev/null</filename> disables the configuration file entirely (it is
+    "masked").</para>
+
+    <para>Along with the link file <filename>foo.link</filename>, a "drop-in" directory
+    <filename>foo.link.d/</filename> may exist. All files with the suffix <literal>.conf</literal>
+    from this directory will be merged in the alphanumeric order and parsed after the main file itself
+    has been parsed. This is useful to alter or add configuration settings, without having to modify
+    the main configuration file. Each drop-in file must have appropriate section headers.</para>
+
+    <para>In addition to <filename>/etc/systemd/network</filename>, drop-in <literal>.d</literal>
+    directories can be placed in <filename>/usr/lib/systemd/network</filename> or
+    <filename>/run/systemd/network</filename> directories. Drop-in files in <filename>/etc/</filename>
+    take precedence over those in <filename>/run/</filename> which in turn take precedence over those
+    in <filename>/usr/lib/</filename>. Drop-in files under any of these directories take precedence
+    over the main link file wherever located.</para>
+
+    <para>The link file contains a [Match] section, which determines if a given link file may be applied to a
+    given device, as well as a [Link] 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
+    <filename>99-default.link</filename> is shipped by the system. Any user-supplied
+    <filename>.link</filename> should hence have a lexically earlier name to be considered at all.</para>
+
+    <para>See <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry> for
+    diagnosing problems with <filename>.link</filename> files.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>[Match] Section Options</title>
+
+    <para>A link file is said to match an interface if all matches specified by the [Match] section are
+    satisfied. When a link file does not contain valid settings in [Match] section, then the file will
+    match all interfaces and <command>systemd-udevd</command> warns about that. Hint: to avoid the
+    warning and to make it clear that all interfaces shall be matched, add the following:
+    <programlisting>OriginalName=*</programlisting>
+    The first (in alphanumeric order) of the link files that matches a given interface is applied, all
+    later files are ignored, even if they match as well. The following keys are accepted:</para>
+
+    <variablelist class='network-directives'>
+      <!-- This list is reused in systemd.network(3), hence maintain a specific order:
+           1. device matches shared between the two lists
+           2. non-shared settings
+           3. host matches shared between the two lists
+        -->
+
+      <varlistentry id='mac-address'>
+        <term><varname>MACAddress=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of hardware addresses. The acceptable formats are:</para>
+
+          <variablelist>
+            <varlistentry>
+              <term><option>colon-delimited hexadecimal</option></term>
+              <listitem><para>
+                Each field must be one byte.
+                E.g. <literal>12:34:56:78:90:ab</literal> or <literal>AA:BB:CC:DD:EE:FF</literal>.
+              </para></listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>hyphen-delimited hexadecimal</option></term>
+              <listitem><para>
+                Each field must be one byte.
+                E.g. <literal>12-34-56-78-90-ab</literal> or <literal>AA-BB-CC-DD-EE-FF</literal>.
+              </para></listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>dot-delimited hexadecimal</option></term>
+              <listitem><para>
+                Each field must be two bytes.
+                E.g. <literal>1234.5678.90ab</literal> or <literal>AABB.CCDD.EEFF</literal>.
+              </para></listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>IPv4 address format</option></term>
+              <listitem><para>
+                E.g. <literal>127.0.0.1</literal> or <literal>192.168.0.1</literal>.
+              </para></listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>IPv6 address format</option></term>
+              <listitem><para>
+                E.g. <literal>2001:0db8:85a3::8a2e:0370:7334</literal> or <literal>::1</literal>.
+              </para></listitem>
+            </varlistentry>
+          </variablelist>
+
+          <para>The total length of each MAC address must be 4 (for IPv4 tunnel), 6 (for Ethernet), 16
+          (for IPv6 tunnel), or 20 (for InfiniBand). This option may appear more than once, in which
+          case the lists are merged. If the empty string is assigned to this option, the list of
+          hardware addresses defined prior to this is reset. Defaults to unset.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='permanent-mac-address'>
+        <term><varname>PermanentMACAddress=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of hardware's permanent addresses. While
+          <varname>MACAddress=</varname> matches the device's current MAC address, this matches the
+          device's permanent MAC address, which may be different from the current one. Use full
+          colon-, hyphen- or dot-delimited hexadecimal, or IPv4 or IPv6 address format. This option may
+          appear more than once, in which case the lists are merged. If the empty string is assigned to
+          this option, the list of hardware addresses defined prior to this is reset. Defaults to
+          unset.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='path'>
+        <term><varname>Path=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of shell-style globs matching
+          the persistent path, as exposed by the udev property
+          <varname>ID_PATH</varname>.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='driver'>
+        <term><varname>Driver=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of shell-style globs matching the driver currently bound to the
+          device, as exposed by the udev property <varname>ID_NET_DRIVER</varname> of its parent device, or
+          if that is not set, the driver as exposed by <command>ethtool -i</command> of the device itself.
+          If the list is prefixed with a "!", the test is inverted.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='type'>
+        <term><varname>Type=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of shell-style globs matching the device type, as exposed by
+          <command>networkctl list</command>. If the list is prefixed with a "!", the test is inverted.
+          Some valid values are <literal>ether</literal>, <literal>loopback</literal>, <literal>wlan</literal>, <literal>wwan</literal>.
+          Valid types are named either from the udev <literal>DEVTYPE</literal> attribute, or
+          <literal>ARPHRD_</literal> macros in <filename>linux/if_arp.h</filename>, so this is not comprehensive.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='kind'>
+        <term><varname>Kind=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of shell-style globs matching the device kind, as exposed by
+          <command>networkctl status <replaceable>INTERFACE</replaceable></command> or
+          <command>ip -d link show <replaceable>INTERFACE</replaceable></command>. If the list is
+          prefixed with a "!", the test is inverted. Some valid values are <literal>bond</literal>,
+          <literal>bridge</literal>, <literal>gre</literal>, <literal>tun</literal>,
+          <literal>veth</literal>. Valid kinds are given by netlink's <literal>IFLA_INFO_KIND</literal>
+          attribute, so this is not comprehensive.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='property'>
+        <term><varname>Property=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of udev property names with their values after equals sign
+          (<literal>=</literal>). If multiple properties are specified, the test results are ANDed.
+          If the list is prefixed with a "!", the test is inverted. If a value contains white
+          spaces, then please quote whole key and value pair. If a value contains quotation, then
+          please escape the quotation with <literal>\</literal>.</para>
+
+          <para>Example: if a .link file has the following:
+          <programlisting>Property=ID_MODEL_ID=9999 "ID_VENDOR_FROM_DATABASE=vendor name" "KEY=with \"quotation\""</programlisting>
+          then, the .link file matches only when an interface has all the above three properties.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>OriginalName=</varname></term>
+        <listitem>
+          <para>A whitespace-separated list of shell-style globs matching the device name, as exposed by the
+          udev property "INTERFACE". This cannot 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.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='host'>
+        <term><varname>Host=</varname></term>
+        <listitem>
+          <para>Matches against the hostname or machine ID of the host. See <varname>ConditionHost=</varname> in
+          <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+          for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
+          If an empty string is assigned, the previously assigned value is cleared.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='virtualization'>
+        <term><varname>Virtualization=</varname></term>
+        <listitem>
+          <para>Checks whether the system is executed in a virtualized environment and optionally test
+          whether it is a specific implementation. See <varname>ConditionVirtualization=</varname> in
+          <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+          for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
+          If an empty string is assigned, the previously assigned value is cleared.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='kernel-command-line'>
+        <term><varname>KernelCommandLine=</varname></term>
+        <listitem>
+          <para>Checks whether a specific kernel command line option is set. See
+          <varname>ConditionKernelCommandLine=</varname> in
+          <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+          for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
+          If an empty string is assigned, the previously assigned value is cleared.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='kernel-version'>
+        <term><varname>KernelVersion=</varname></term>
+        <listitem>
+          <para>Checks whether the kernel version (as reported by <command>uname -r</command>) matches a certain
+          expression. See <varname>ConditionKernelVersion=</varname> in
+          <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
+          details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
+          If an empty string is assigned, the previously assigned value is cleared.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='credential'>
+        <term><varname>Credential=</varname></term>
+        <listitem>
+          <para>Checks whether the specified credential was passed to the
+          <filename>systemd-networkd.service</filename> service. See <ulink
+          url="https://systemd.io/CREDENTIALS">System and Service Credentials</ulink> for details. When
+          prefixed with an exclamation mark (<literal>!</literal>), the result is negated.  If an empty
+          string is assigned, the previously assigned value is cleared.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='architecture'>
+        <term><varname>Architecture=</varname></term>
+        <listitem>
+          <para>Checks whether the system is running on a specific architecture. See
+          <varname>ConditionArchitecture=</varname> in
+          <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+          for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
+          If an empty string is assigned, the previously assigned value is cleared.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry id='firmware'>
+        <term><varname>Firmware=</varname></term>
+        <listitem>
+          <para>Checks whether the system is running on a machine with the specified firmware. See
+          <varname>ConditionFirmware=</varname> in
+          <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+          for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
+          If an empty string is assigned, the previously assigned value is cleared.
+          </para>
+        </listitem>
+      </varlistentry>
+    </variablelist>
+
+  </refsect1>
+
+  <refsect1>
+    <title>[Link] Section Options</title>
+
+    <para>The [Link] section accepts the following
+    keys:</para>
+
+    <variablelist class='network-directives'>
+      <varlistentry>
+        <term><varname>Description=</varname></term>
+        <listitem>
+          <para>A description of the device.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>Alias=</varname></term>
+        <listitem>
+          <para>The <varname>ifalias</varname> interface property is set to this value.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>MACAddressPolicy=</varname></term>
+        <listitem>
+          <para>The policy by which the MAC address should be set. The
+          available policies are:
+          </para>
+
+          <variablelist>
+            <varlistentry>
+              <term><option>persistent</option></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 to exist 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><option>random</option></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. Either way, the random address will have the
+                <literal>unicast</literal> and
+                <literal>locally administered</literal> bits set.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>none</option></term>
+              <listitem>
+                <para>Keeps the MAC address assigned by the kernel. Or use the MAC address specified in
+                <varname>MACAddress=</varname>.</para>
+              </listitem>
+            </varlistentry>
+          </variablelist>
+
+          <para>An empty string assignment is equivalent to setting <literal>none</literal>.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>MACAddress=</varname></term>
+        <listitem>
+          <para>The interface MAC address to use. For this setting to take effect,
+          <varname>MACAddressPolicy=</varname> must either be unset, empty, or <literal>none</literal>.
+          </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.
+          <varname>NamePolicy=</varname> may be disabled by specifying <option>net.ifnames=0</option> 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 <option>ID_NET_NAME</option>, which
+          is, by default, used by a
+          <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+          rule to set <varname>NAME</varname>. The available policies are:
+          </para>
+
+          <variablelist>
+            <varlistentry>
+              <term><option>kernel</option></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><option>database</option></term>
+              <listitem>
+                <para>The name is set based on entries in the udev's
+                Hardware Database with the key
+                <varname>ID_NET_NAME_FROM_DATABASE</varname>.
+                </para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>onboard</option></term>
+              <listitem>
+                <para>The name is set based on information given by
+                the firmware for on-board devices, as exported by the
+                udev property <varname>ID_NET_NAME_ONBOARD</varname>.
+                See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+                </para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>slot</option></term>
+              <listitem>
+                <para>The name is set based on information given by
+                the firmware for hot-plug devices, as exported by the
+                udev property <varname>ID_NET_NAME_SLOT</varname>.
+                See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+                </para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>path</option></term>
+              <listitem>
+                <para>The name is set based on the device's physical
+                location, as exported by the udev property
+                <varname>ID_NET_NAME_PATH</varname>.
+                See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+                </para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>mac</option></term>
+              <listitem>
+                <para>The name is set based on the device's persistent
+                MAC address, as exported by the udev property
+                <varname>ID_NET_NAME_MAC</varname>.
+                See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+                </para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>keep</option></term>
+              <listitem>
+                <para>If the device already had a name given by userspace (as part of creation of the device
+                or a rename), keep it.</para>
+              </listitem>
+            </varlistentry>
+          </variablelist>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>Name=</varname></term>
+        <listitem>
+          <para>The interface name to use. This option has lower precedence than
+          <varname>NamePolicy=</varname>, so for this setting to take effect, <varname>NamePolicy=</varname>
+          must either be unset, empty, disabled, or all policies configured there must fail. Also see the
+          example below with <literal>Name=dmz0</literal>.</para>
+
+          <para>Note that specifying a name that the kernel might use for another interface (for example
+          <literal>eth0</literal>) is dangerous because the name assignment done by udev will race with the
+          assignment done by the kernel, and only one interface may use the name. Depending on the order of
+          operations, either udev or the kernel will win, making the naming unpredictable. It is best to use
+          some different prefix, for example <literal>internal0</literal>/<literal>external0</literal> or
+          <literal>lan0</literal>/<literal>lan1</literal>/<literal>lan3</literal>.</para>
+
+          <para>Interface names must have a minimum length of 1 character and a maximum length of 15
+          characters, and may contain any 7bit ASCII character, with the exception of control characters,
+          <literal>:</literal>, <literal>/</literal> and <literal>%</literal>. While <literal>.</literal> is
+          an allowed character, it's recommended to avoid it when naming interfaces as various tools (such as
+          <citerefentry><refentrytitle>resolvconf</refentrytitle><manvolnum>1</manvolnum></citerefentry>) use
+          it as separator character. Also, fully numeric interface names are not allowed (in order to avoid
+          ambiguity with interface specification by numeric indexes), as are the special strings
+          <literal>.</literal>, <literal>..</literal>, <literal>all</literal> and
+          <literal>default</literal>.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>AlternativeNamesPolicy=</varname></term>
+        <listitem>
+          <para>A space-separated list of policies by which the interface's alternative names
+          should be set. Each of the policies may fail, and all successful policies are used. The
+          available policies are <literal>database</literal>, <literal>onboard</literal>,
+          <literal>slot</literal>, <literal>path</literal>, and <literal>mac</literal>. If the
+          kernel does not support the alternative names, then this setting will be ignored.
+          </para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>AlternativeName=</varname></term>
+        <listitem>
+          <para>The alternative interface name to use. This option can be specified multiple times.
+          If the empty string is assigned to this option, the list is reset, and all prior assignments
+          have no effect. If the kernel does not support the alternative names, then this setting will
+          be ignored.</para>
+
+          <para>Alternative interface names may be used to identify interfaces in various tools. In contrast
+          to the primary name (as configured with <varname>Name=</varname> above) there may be multiple
+          alternative names referring to the same interface. Alternative names may have a maximum length of
+          127 characters, in contrast to the 15 allowed for the primary interface name, but otherwise are
+          subject to the same naming constraints.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TransmitQueues=</varname></term>
+        <listitem>
+          <para>Specifies the device's number of transmit queues. An integer in the range 1…4096.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>ReceiveQueues=</varname></term>
+        <listitem>
+          <para>Specifies the device's number of receive queues. An integer in the range 1…4096.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TransmitQueueLength=</varname></term>
+        <listitem>
+          <para>Specifies the transmit queue length of the device in number of packets. An unsigned integer
+          in the range 0…4294967294. When unset, the kernel's default will be used.</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 <option>half</option> and
+          <option>full</option>.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>AutoNegotiation=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to yes, automatic negotiation of transmission parameters is enabled.
+          Autonegotiation is a procedure by which two connected ethernet devices choose
+          common transmission parameters, such as speed, duplex mode, and flow control.
+          When unset, the kernel's default will be used.</para>
+
+          <para>Note that if autonegotiation is enabled, speed and duplex settings are
+          read-only. If autonegotiation is disabled, speed and duplex settings are writable
+          if the driver supports multiple link modes.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>WakeOnLan=</varname></term>
+        <listitem>
+          <para>The Wake-on-LAN policy to set for the device. Takes the special value
+          <literal>off</literal> which disables Wake-on-LAN, or space separated list of the following
+          words:</para>
+
+          <variablelist>
+            <varlistentry>
+              <term><option>phy</option></term>
+              <listitem>
+                <para>Wake on PHY activity.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>unicast</option></term>
+              <listitem>
+                <para>Wake on unicast messages.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>multicast</option></term>
+              <listitem>
+                <para>Wake on multicast messages.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>broadcast</option></term>
+              <listitem>
+                <para>Wake on broadcast messages.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>arp</option></term>
+              <listitem>
+                <para>Wake on ARP.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>magic</option></term>
+              <listitem>
+                <para>Wake on receipt of a magic packet.
+                </para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>secureon</option></term>
+              <listitem>
+                <para>Enable SecureOn password for MagicPacket. Implied when
+                <varname>WakeOnLanPassword=</varname> is specified. If specified without
+                <varname>WakeOnLanPassword=</varname> option, then the password is read from the
+                credential <literal><replaceable>LINK</replaceable>.link.wol.password</literal> (e.g.,
+                <literal>60-foo.link.wol.password</literal>), and if the credential not found, then
+                read from <literal>wol.password</literal>. See
+                <varname>LoadCredential=</varname>/<varname>SetCredential=</varname> in
+                <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                for details. The password in the credential, must be 6 bytes in hex format with each
+                byte separated by a colon (<literal>:</literal>) like an Ethernet MAC address, e.g.,
+                <literal>aa:bb:cc:dd:ee:ff</literal>.</para>
+              </listitem>
+            </varlistentry>
+          </variablelist>
+
+          <para>Defaults to unset, and the device's default will be used. This setting can be specified
+          multiple times. If an empty string is assigned, then the all previous assignments are
+          cleared.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>WakeOnLanPassword=</varname></term>
+        <listitem>
+          <para>Specifies the SecureOn password for MagicPacket. Takes an absolute path to a regular
+          file or an <constant>AF_UNIX</constant> stream socket, or the plain password. When a path to
+          a regular file is specified, the password is read from it. When an
+          <constant>AF_UNIX</constant> stream socket is specified, a connection is made to it and the
+          password is read from it. The password must be 6 bytes in hex format with each byte separated
+          by a colon (<literal>:</literal>) like an Ethernet MAC address, e.g.,
+          <literal>aa:bb:cc:dd:ee:ff</literal>. This implies <varname>WakeOnLan=secureon</varname>.
+          Defaults to unset, and the current value will not be changed.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>Port=</varname></term>
+        <listitem>
+          <para>The port option is used to select the device port. The
+          supported values are:</para>
+
+          <variablelist>
+            <varlistentry>
+              <term><option>tp</option></term>
+              <listitem>
+                <para>An Ethernet interface using Twisted-Pair cable as the medium.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>aui</option></term>
+              <listitem>
+                <para>Attachment Unit Interface (AUI). Normally used with hubs.
+                </para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>bnc</option></term>
+              <listitem>
+                <para>An Ethernet interface using BNC connectors and co-axial cable.</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>mii</option></term>
+              <listitem>
+                <para>An Ethernet interface using a Media Independent Interface (MII).</para>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term><option>fibre</option></term>
+              <listitem>
+                <para>An Ethernet interface using Optical Fibre as the medium.</para>
+              </listitem>
+            </varlistentry>
+          </variablelist>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>Advertise=</varname></term>
+        <listitem>
+          <para>This sets what speeds and duplex modes of operation are advertised for auto-negotiation.
+          This implies <literal>AutoNegotiation=yes</literal>. The supported values are:
+
+          <table>
+            <title>Supported advertise values</title>
+            <tgroup cols='3'>
+              <colspec colname='Advertise' />
+              <colspec colname='Speed' />
+              <colspec colname='Duplex Mode' />
+
+              <thead><row>
+                <entry>Advertise</entry>
+                <entry>Speed (Mbps)</entry>
+                <entry>Duplex Mode</entry>
+              </row></thead>
+              <tbody>
+                <row><entry><option>10baset-half</option></entry>
+                <entry>10</entry><entry>half</entry></row>
+
+                <row><entry><option>10baset-full</option></entry>
+                <entry>10</entry><entry>full</entry></row>
+
+                <row><entry><option>100baset-half</option></entry>
+                <entry>100</entry><entry>half</entry></row>
+
+                <row><entry><option>100baset-full</option></entry>
+                <entry>100</entry><entry>full</entry></row>
+
+                <row><entry><option>1000baset-half</option></entry>
+                <entry>1000</entry><entry>half</entry></row>
+
+                <row><entry><option>1000baset-full</option></entry>
+                <entry>1000</entry><entry>full</entry></row>
+
+                <row><entry><option>10000baset-full</option></entry>
+                <entry>10000</entry><entry>full</entry></row>
+
+                <row><entry><option>2500basex-full</option></entry>
+                <entry>2500</entry><entry>full</entry></row>
+
+                <row><entry><option>1000basekx-full</option></entry>
+                <entry>1000</entry><entry>full</entry></row>
+
+                <row><entry><option>10000basekx4-full</option></entry>
+                <entry>10000</entry><entry>full</entry></row>
+
+                <row><entry><option>10000basekr-full</option></entry>
+                <entry>10000</entry><entry>full</entry></row>
+
+                <row><entry><option>10000baser-fec</option></entry>
+                <entry>10000</entry><entry>full</entry></row>
+
+                <row><entry><option>20000basemld2-full</option></entry>
+                <entry>20000</entry><entry>full</entry></row>
+
+                <row><entry><option>20000basekr2-full</option></entry>
+                <entry>20000</entry><entry>full</entry></row>
+              </tbody>
+            </tgroup>
+          </table>
+
+          By default this is unset, i.e. all possible modes will be advertised.
+          This option may be specified more than once, in which case all specified speeds and modes are advertised.
+          If the empty string is assigned to this option, the list is reset, and all prior assignments have no effect.
+          </para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>ReceiveChecksumOffload=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, hardware offload for checksumming of ingress
+          network packets is enabled. When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TransmitChecksumOffload=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, hardware offload for checksumming of egress
+          network packets is enabled. When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TCPSegmentationOffload=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, TCP Segmentation Offload (TSO) is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+       <varlistentry>
+      <term><varname>TCP6SegmentationOffload=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, TCP6 Segmentation Offload (tx-tcp6-segmentation) is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>GenericSegmentationOffload=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, Generic Segmentation Offload (GSO) is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>GenericReceiveOffload=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, Generic Receive Offload (GRO) is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>GenericReceiveOffloadHardware=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, hardware accelerated Generic Receive Offload (GRO) is
+          enabled. When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>LargeReceiveOffload=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, Large Receive Offload (LRO) is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>ReceiveVLANCTAGHardwareAcceleration=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, receive VLAN CTAG hardware acceleration is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TransmitVLANCTAGHardwareAcceleration=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, transmit VLAN CTAG hardware acceleration is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>ReceiveVLANCTAGFilter=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, receive filtering on VLAN CTAGs is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TransmitVLANSTAGHardwareAcceleration=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, transmit VLAN STAG hardware acceleration is enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>NTupleFilter=</varname></term>
+        <listitem>
+          <para>Takes a boolean. If set to true, receive N-tuple filters and actions are enabled.
+          When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>RxChannels=</varname></term>
+        <term><varname>TxChannels=</varname></term>
+        <term><varname>OtherChannels=</varname></term>
+        <term><varname>CombinedChannels=</varname></term>
+        <listitem>
+          <para>Specifies the number of receive, transmit, other, or combined channels, respectively.
+          Takes an unsigned integer in the range 1…4294967295 or <literal>max</literal>. If set to
+          <literal>max</literal>, the advertised maximum value of the hardware will be used. When
+          unset, the number will not be changed. Defaults to unset.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>RxBufferSize=</varname></term>
+        <term><varname>RxMiniBufferSize=</varname></term>
+        <term><varname>RxJumboBufferSize=</varname></term>
+        <term><varname>TxBufferSize=</varname></term>
+        <listitem>
+          <para>Specifies the maximum number of pending packets in the NIC receive buffer, mini receive
+          buffer, jumbo receive buffer, or transmit buffer, respectively. Takes an unsigned integer in
+          the range 1…4294967295 or <literal>max</literal>. If set to <literal>max</literal>, the
+          advertised maximum value of the hardware will be used. When unset, the number will not be
+          changed. Defaults to unset.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>RxFlowControl=</varname></term>
+        <listitem>
+          <para>Takes a boolean. When set, enables receive flow control, also known as the ethernet
+          receive PAUSE message (generate and send ethernet PAUSE frames). When unset, the kernel's
+          default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>TxFlowControl=</varname></term>
+        <listitem>
+          <para>Takes a boolean. When set, enables transmit flow control, also known as the ethernet
+          transmit PAUSE message (respond to received ethernet PAUSE frames). When unset, the kernel's
+          default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>AutoNegotiationFlowControl=</varname></term>
+        <listitem>
+          <para>Takes a boolean. When set, auto negotiation enables the interface to exchange state
+          advertisements with the connected peer so that the two devices can agree on the ethernet
+          PAUSE configuration. When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>GenericSegmentOffloadMaxBytes=</varname></term>
+        <listitem>
+          <para>Specifies the maximum size of a Generic Segment Offload (GSO) packet the
+          device should accept. The usual suffixes K, M, G are supported and are
+          understood to the base of 1024. An unsigned integer in the range 1…65536.
+          Defaults to unset.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>GenericSegmentOffloadMaxSegments=</varname></term>
+        <listitem>
+          <para>Specifies the maximum number of Generic Segment Offload (GSO) segments the device should
+          accept. An unsigned integer in the range 1…65535. Defaults to unset.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>UseAdaptiveRxCoalesce=</varname></term>
+        <term><varname>UseAdaptiveTxCoalesce=</varname></term>
+        <listitem>
+          <para>Boolean properties that, when set, enable/disable adaptive Rx/Tx coalescing if the hardware
+          supports it. When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>RxCoalesceSec=</varname></term>
+        <term><varname>RxCoalesceIrqSec=</varname></term>
+        <term><varname>RxCoalesceLowSec=</varname></term>
+        <term><varname>RxCoalesceHighSec=</varname></term>
+        <term><varname>TxCoalesceSec=</varname></term>
+        <term><varname>TxCoalesceIrqSec=</varname></term>
+        <term><varname>TxCoalesceLowSec=</varname></term>
+        <term><varname>TxCoalesceHighSec=</varname></term>
+        <listitem>
+          <para>These properties configure the delay before Rx/Tx interrupts are generated after a packet is
+          sent/received. The <literal>Irq</literal> properties come into effect when the host is servicing an
+          IRQ. The <literal>Low</literal> and <literal>High</literal> properties come into effect when the
+          packet rate drops below the low packet rate threshold or exceeds the high packet rate threshold
+          respectively if adaptive Rx/Tx coalescing is enabled. When unset, the kernel's defaults will be
+          used.</para>
+        </listitem>
+      </varlistentry>
+        <varlistentry>
+        <term><varname>RxMaxCoalescedFrames=</varname></term>
+        <term><varname>RxMaxCoalescedIrqFrames=</varname></term>
+        <term><varname>RxMaxCoalescedLowFrames=</varname></term>
+        <term><varname>RxMaxCoalescedHighFrames=</varname></term>
+        <term><varname>TxMaxCoalescedFrames=</varname></term>
+        <term><varname>TxMaxCoalescedIrqFrames=</varname></term>
+        <term><varname>TxMaxCoalescedLowFrames=</varname></term>
+        <term><varname>TxMaxCoalescedHighFrames=</varname></term>
+        <listitem>
+          <para>These properties configure the maximum number of frames that are sent/received before a Rx/Tx
+          interrupt is generated. The <literal>Irq</literal> properties come into effect when the host is
+          servicing an IRQ. The <literal>Low</literal> and <literal>High</literal> properties come into
+          effect when the packet rate drops below the low packet rate threshold or exceeds the high packet
+          rate threshold respectively if adaptive Rx/Tx coalescing is enabled. When unset, the kernel's
+          defaults will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>CoalescePacketRateLow=</varname></term>
+        <term><varname>CoalescePacketRateHigh=</varname></term>
+        <listitem>
+          <para>These properties configure the low and high packet rate (expressed in packets per second)
+          threshold respectively and are used to determine when the corresponding coalescing settings for low
+          and high packet rates come into effect if adaptive Rx/Tx coalescing is enabled. If unset, the
+          kernel's defaults will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>CoalescePacketRateSampleIntervalSec=</varname></term>
+        <listitem>
+          <para>Configures how often to sample the packet rate used for adaptive Rx/Tx coalescing. This
+          property cannot be zero. This lowest time granularity supported by this property is seconds.
+          Partial seconds will be rounded up before being passed to the kernel. If unset, the kernel's
+          default will be used.</para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term><varname>StatisticsBlockCoalesceSec=</varname></term>
+        <listitem>
+          <para>How long to delay driver in-memory statistics block updates. If the driver does not have an
+          in-memory statistic block, this property is ignored. This property cannot be zero. If unset, the
+          kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>MDI=</varname></term>
+        <listitem>
+          <para>Specifies the medium dependent interface (MDI) mode for the interface. A MDI describes
+          the interface from a physical layer implementation to the physical medium used to carry the
+          transmission. Takes one of the following words: <literal>straight</literal> (or equivalently:
+          <literal>mdi</literal>), <literal>crossover</literal> (or equivalently:
+          <literal>mdi-x</literal>, <literal>mdix</literal>), and <literal>auto</literal>. When
+          <literal>straight</literal>, the MDI straight through mode will be used. When
+          <literal>crossover</literal>, the MDI crossover (MDI-X) mode will be used. When
+          <literal>auto</literal>, the MDI status is automatically detected. Defaults to unset, and the
+          kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>SR-IOVVirtualFunctions=</varname></term>
+        <listitem>
+          <para>Specifies the number of SR-IOV virtual functions. Takes an integer in the range
+          0…2147483647. Defaults to unset, and automatically determined from the values specified in
+          the <varname>VirtualFunction=</varname> settings in the [SR-IOV] sections.</para>
+        </listitem>
+      </varlistentry>
+
+    </variablelist>
+  </refsect1>
+
+  <refsect1 id='sr-iov'>
+    <title>[SR-IOV] Section Options</title>
+    <para>The [SR-IOV] section accepts the following keys. Specify several [SR-IOV] sections to
+    configure several SR-IOVs. SR-IOV provides the ability to partition a single physical PCI resource
+    into virtual PCI functions which can then be injected into a VM. In the case of network VFs, SR-IOV
+    improves north-south network performance (that is, traffic with endpoints outside the host machine)
+    by allowing traffic to bypass the host machine’s network stack.</para>
+
+    <variablelist class='network-directives'>
+      <varlistentry>
+        <term><varname>VirtualFunction=</varname></term>
+        <listitem>
+          <para>Specifies a Virtual Function (VF), lightweight PCIe function designed solely to move
+          data in and out. Takes an integer in the range 0…2147483646. This option is compulsory.
+          </para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>VLANId=</varname></term>
+        <listitem>
+          <para>Specifies VLAN ID of the virtual function. Takes an integer in the range 1…4095.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>QualityOfService=</varname></term>
+        <listitem>
+          <para>Specifies quality of service of the virtual function. Takes an integer in the range
+          1…4294967294.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>VLANProtocol=</varname></term>
+        <listitem>
+          <para>Specifies VLAN protocol of the virtual function. Takes <literal>802.1Q</literal> or
+          <literal>802.1ad</literal>.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>MACSpoofCheck=</varname></term>
+        <listitem>
+          <para>Takes a boolean. Controls the MAC spoof checking. When unset, the kernel's default will
+          be used.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>QueryReceiveSideScaling=</varname></term>
+        <listitem>
+          <para>Takes a boolean. Toggle the ability of querying the receive side scaling (RSS)
+          configuration of the virtual function (VF). The VF RSS information like RSS hash key may be
+          considered sensitive on some devices where this information is shared between VF and the
+          physical function (PF). When unset, the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>Trust=</varname></term>
+        <listitem>
+          <para>Takes a boolean. Allows one to set trust mode of the virtual function (VF). When set,
+          VF users can set a specific feature which may impact security and/or performance. When unset,
+          the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>LinkState=</varname></term>
+        <listitem>
+          <para>Allows one to set the link state of the virtual function (VF). Takes a boolean or a
+          special value <literal>auto</literal>. Setting to <literal>auto</literal> means a
+          reflection of the physical function (PF) link state, <literal>yes</literal> lets the VF to
+          communicate with other VFs on this host even if the PF link state is down,
+          <literal>no</literal> causes the hardware to drop any packets sent by the VF. When unset,
+          the kernel's default will be used.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>MACAddress=</varname></term>
+        <listitem>
+          <para>Specifies the MAC address for the virtual function.</para>
+        </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Examples</title>
+
+    <example>
+      <title>/usr/lib/systemd/network/99-default.link</title>
+
+      <para>The link file <filename>99-default.link</filename> that is
+      shipped with systemd defines the default naming policy for
+      links.</para>
+
+      <programlisting>[Link]
+NamePolicy=kernel database onboard slot path
+MACAddressPolicy=persistent</programlisting>
+    </example>
+
+    <example>
+      <title>/etc/systemd/network/10-dmz.link</title>
+
+      <para>This example assigns the fixed name <literal>dmz0</literal> to the interface with the MAC address
+      00:a0:de:63:7a:e6:</para>
+
+      <programlisting>[Match]
+MACAddress=00:a0:de:63:7a:e6
+
+[Link]
+Name=dmz0</programlisting>
+
+      <para><varname>NamePolicy=</varname> is not set, so <varname>Name=</varname> takes effect. We use the
+      <literal>10-</literal> prefix to order this file early in the list. Note that it needs to be before
+      <literal>99-link</literal>, i.e. it needs a numerical prefix, to have any effect at all.</para>
+    </example>
+
+    <example>
+      <title>Debugging <varname>NamePolicy=</varname> assignments</title>
+
+      <programlisting>$ sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/hub0
+…
+Parsed configuration file /usr/lib/systemd/network/99-default.link
+Parsed configuration file /etc/systemd/network/10-eth0.link
+ID_NET_DRIVER=cdc_ether
+Config file /etc/systemd/network/10-eth0.link applies to device hub0
+link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
+hub0: Device has name_assign_type=4
+Using default interface naming scheme 'v240'.
+hub0: Policies didn't yield a name, using specified Name=hub0.
+ID_NET_LINK_FILE=/etc/systemd/network/10-eth0.link
+ID_NET_NAME=hub0
+…</programlisting>
+
+     <para>Explicit <varname>Name=</varname> configuration wins in this case.</para>
+
+     <programlisting>sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/enp0s31f6
+…
+Parsed configuration file /usr/lib/systemd/network/99-default.link
+Parsed configuration file /etc/systemd/network/10-eth0.link
+Created link configuration context.
+ID_NET_DRIVER=e1000e
+Config file /usr/lib/systemd/network/99-default.link applies to device enp0s31f6
+link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
+enp0s31f6: Device has name_assign_type=4
+Using default interface naming scheme 'v240'.
+enp0s31f6: Policy *keep*: keeping existing userspace name
+enp0s31f6: Device has addr_assign_type=0
+enp0s31f6: MAC on the device already matches policy *persistent*
+ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
+…
+</programlisting>
+
+     <para>In this case, the interface was already renamed, so the <option>keep</option> policy specified as
+     the first option in <filename index="false">99-default.link</filename> means that the existing name is
+     preserved. If <option>keep</option> was removed, or if were in boot before the renaming has happened,
+     we might get the following instead:</para>
+
+     <programlisting>enp0s31f6: Policy *path* yields "enp0s31f6".
+enp0s31f6: Device has addr_assign_type=0
+enp0s31f6: MAC on the device already matches policy *persistent*
+ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
+ID_NET_NAME=enp0s31f6
+…
+</programlisting>
+
+      <para>Please note that the details of output are subject to change.</para>
+    </example>
+
+    <example>
+      <title>/etc/systemd/network/10-internet.link</title>
+
+      <para>This example assigns the fixed name
+      <literal>internet0</literal> to the interface with the device
+      path <literal>pci-0000:00:1a.0-*</literal>:</para>
+
+      <programlisting>[Match]
+Path=pci-0000:00:1a.0-*
+
+[Link]
+Name=internet0</programlisting>
+    </example>
+
+    <example>
+      <title>/etc/systemd/network/25-wireless.link</title>
+
+      <para>Here's an overly complex example that shows the use of a large number of [Match] and [Link] settings.</para>
+
+      <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>,
+      <citerefentry>
+        <refentrytitle>systemd-network-generator.service</refentrytitle><manvolnum>8</manvolnum>
+      </citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>