man/systemd.link.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="systemd.link">
   7   <refentryinfo>
   8     <title>systemd.link</title>
   9     <productname>systemd</productname>
  10   </refentryinfo>
  11
  12   <refmeta>
  13     <refentrytitle>systemd.link</refentrytitle>
  14     <manvolnum>5</manvolnum>
  15   </refmeta>
  16
  17   <refnamediv>
  18     <refname>systemd.link</refname>
  19     <refpurpose>Network device configuration</refpurpose>
  20   </refnamediv>
  21
  22   <refsynopsisdiv>
  23     <para><filename><replaceable>link</replaceable>.link</filename></para>
  24   </refsynopsisdiv>
  25
  26   <refsect1>
  27     <title>Description</title>
  28
  29     <para>Network link configuration is performed by the
  30     <command>net_setup_link</command> udev builtin.</para>
  31
  32     <para>The link files are read from the files located in the system
  33     network directory <filename>/usr/lib/systemd/network</filename>,
  34     the volatile runtime network directory
  35     <filename>/run/systemd/network</filename>, and the local
  36     administration network directory
  37     <filename>/etc/systemd/network</filename>. Link files must have
  38     the extension <filename>.link</filename>; other extensions are
  39     ignored. All link files are collectively sorted and processed in
  40     lexical order, regardless of the directories in which they live.
  41     However, files with identical filenames replace each other. Files
  42     in <filename>/etc</filename> have the highest priority, files in
  43     <filename>/run</filename> take precedence over files with the same
  44     name in <filename>/usr/lib</filename>. This can be used to
  45     override a system-supplied link file with a local file if needed.
  46     As a special case, an empty file (file size 0) or symlink with the
  47     same name pointing to <filename>/dev/null</filename> disables the
  48     configuration file entirely (it is "masked").</para>
  49
  50     <para>The link file contains a [Match] section, which determines if a given link file may be applied to a
  51     given device, as well as a [Link] section specifying how the device should be configured. The first (in
  52     lexical order) of the link files that matches a given device is applied. Note that a default file
  53     <filename>99-default.link</filename> is shipped by the system. Any user-supplied
  54     <filename>.link</filename> should hence have a lexically earlier name to be considered at all.</para>
  55
  56     <para>See <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry> for
  57     diagnosing problems with <filename>.link</filename> files.</para>
  58   </refsect1>
  59
  60   <refsect1>
  61     <title>[Match] Section Options</title>
  62
  63     <para>A link file is said to match a device if each of the entries in the [Match] section matches, or if
  64     the section is empty. The following keys are accepted:</para>
  65
  66     <variablelist class='network-directives'>
  67       <varlistentry>
  68         <term><varname>MACAddress=</varname></term>
  69         <listitem>
  70           <para>A whitespace-separated list of hardware addresses. Use full colon-, hyphen- or dot-delimited hexadecimal. See the example below.
  71           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
  72           of hardware addresses defined prior to this is reset.</para>
  73
  74           <para>Example:
  75           <programlisting>MACAddress=01:23:45:67:89:ab 00-11-22-33-44-55 AABB.CCDD.EEFF</programlisting></para>
  76         </listitem>
  77       </varlistentry>
  78       <varlistentry>
  79         <term><varname>OriginalName=</varname></term>
  80         <listitem>
  81           <para>A whitespace-separated list of shell-style globs matching
  82           the device name, as exposed by the udev property
  83           "INTERFACE". This cannot be used to match on names that have
  84           already been changed from userspace. Caution is advised when matching on
  85           kernel-assigned names, as they are known to be unstable
  86           between reboots.</para>
  87         </listitem>
  88       </varlistentry>
  89       <varlistentry>
  90         <term><varname>Path=</varname></term>
  91         <listitem>
  92           <para>A whitespace-separated list of shell-style globs matching
  93           the persistent path, as exposed by the udev property
  94           <varname>ID_PATH</varname>.</para>
  95         </listitem>
  96       </varlistentry>
  97       <varlistentry>
  98         <term><varname>Driver=</varname></term>
  99         <listitem>
 100           <para>A whitespace-separated list of shell-style globs matching the driver currently bound to the
 101           device, as exposed by the udev property <varname>DRIVER</varname> of its parent device, or if that
 102           is not set, the driver as exposed by <command>ethtool -i</command> of the device itself.</para>
 103         </listitem>
 104       </varlistentry>
 105       <varlistentry>
 106         <term><varname>Type=</varname></term>
 107         <listitem>
 108           <para>A whitespace-separated list of shell-style globs matching
 109           the device type, as exposed by the udev
 110           property <varname>DEVTYPE</varname>.</para>
 111         </listitem>
 112       </varlistentry>
 113       <varlistentry>
 114         <term><varname>Host=</varname></term>
 115         <listitem>
 116           <para>Matches against the hostname or machine ID of the host. See <varname>ConditionHost=</varname> in
 117           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 118           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 119           If an empty string is assigned, then previously assigned value is cleared.
 120           </para>
 121         </listitem>
 122       </varlistentry>
 123       <varlistentry>
 124         <term><varname>Virtualization=</varname></term>
 125         <listitem>
 126           <para>Checks whether the system is executed in a virtualized environment and optionally test
 127           whether it is a specific implementation. See <varname>ConditionVirtualization=</varname> in
 128           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 129           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 130           If an empty string is assigned, then previously assigned value is cleared.
 131           </para>
 132         </listitem>
 133       </varlistentry>
 134       <varlistentry>
 135         <term><varname>KernelCommandLine=</varname></term>
 136         <listitem>
 137           <para>Checks whether a specific kernel command line option is set. See
 138           <varname>ConditionKernelCommandLine=</varname> in
 139           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 140           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 141           If an empty string is assigned, then previously assigned value is cleared.
 142           </para>
 143         </listitem>
 144       </varlistentry>
 145       <varlistentry>
 146         <term><varname>KernelVersion=</varname></term>
 147         <listitem>
 148           <para>Checks whether the kernel version (as reported by <command>uname -r</command>) matches a certain
 149           expression. See <varname>ConditionKernelVersion=</varname> in
 150           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 151           details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 152           If an empty string is assigned, then previously assigned value is cleared.
 153           </para>
 154         </listitem>
 155       </varlistentry>
 156       <varlistentry>
 157         <term><varname>Architecture=</varname></term>
 158         <listitem>
 159           <para>Checks whether the system is running on a specific architecture. See
 160           <varname>ConditionArchitecture=</varname> in
 161           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 162           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 163           If an empty string is assigned, then previously assigned value is cleared.
 164           </para>
 165         </listitem>
 166       </varlistentry>
 167     </variablelist>
 168
 169   </refsect1>
 170
 171   <refsect1>
 172     <title>[Link] Section Options</title>
 173
 174     <para>The [Link] section accepts the following
 175     keys:</para>
 176
 177     <variablelist class='network-directives'>
 178       <varlistentry>
 179         <term><varname>Description=</varname></term>
 180         <listitem>
 181           <para>A description of the device.</para>
 182         </listitem>
 183       </varlistentry>
 184       <varlistentry>
 185         <term><varname>Alias=</varname></term>
 186         <listitem>
 187           <para>The <varname>ifalias</varname> interface property is set to this value.</para>
 188         </listitem>
 189       </varlistentry>
 190       <varlistentry>
 191         <term><varname>MACAddressPolicy=</varname></term>
 192         <listitem>
 193           <para>The policy by which the MAC address should be set. The
 194           available policies are:
 195           </para>
 196
 197           <variablelist>
 198             <varlistentry>
 199               <term><option>persistent</option></term>
 200               <listitem>
 201                 <para>If the hardware has a persistent MAC address, as
 202                 most hardware should, and if it is used by the kernel,
 203                 nothing is done. Otherwise, a new MAC address is
 204                 generated which is guaranteed to be the same on every
 205                 boot for the given machine and the given device, but
 206                 which is otherwise random. This feature depends on ID_NET_NAME_*
 207                 properties to exist for the link. On hardware where these
 208                 properties are not set, the generation of a persistent MAC address
 209                 will fail.</para>
 210               </listitem>
 211             </varlistentry>
 212             <varlistentry>
 213               <term><option>random</option></term>
 214               <listitem>
 215                 <para>If the kernel is using a random MAC address,
 216                 nothing is done. Otherwise, a new address is randomly
 217                 generated each time the device appears, typically at
 218                 boot. Either way, the random address will have the
 219                 <literal>unicast</literal> and
 220                 <literal>locally administered</literal> bits set.</para>
 221               </listitem>
 222             </varlistentry>
 223             <varlistentry>
 224               <term><option>none</option></term>
 225               <listitem>
 226                 <para>Keeps the MAC address assigned by the kernel.</para>
 227               </listitem>
 228             </varlistentry>
 229           </variablelist>
 230         </listitem>
 231       </varlistentry>
 232       <varlistentry>
 233         <term><varname>MACAddress=</varname></term>
 234         <listitem>
 235           <para>The MAC address to use, if no
 236           <varname>MACAddressPolicy=</varname>
 237           is specified.</para>
 238         </listitem>
 239       </varlistentry>
 240       <varlistentry>
 241         <term><varname>NamePolicy=</varname></term>
 242         <listitem>
 243           <para>An ordered, space-separated list of policies by which the interface name should be set.
 244           <varname>NamePolicy=</varname> may be disabled by specifying <option>net.ifnames=0</option> on the
 245           kernel command line. Each of the policies may fail, and the first successful one is used. The name
 246           is not set directly, but is exported to udev as the property <option>ID_NET_NAME</option>, which
 247           is, by default, used by a
 248           <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 249           rule to set <varname>NAME</varname>. The available policies are:
 250           </para>
 251
 252           <variablelist>
 253             <varlistentry>
 254               <term><option>kernel</option></term>
 255               <listitem>
 256                 <para>If the kernel claims that the name it has set
 257                 for a device is predictable, then no renaming is
 258                 performed.</para>
 259               </listitem>
 260             </varlistentry>
 261             <varlistentry>
 262               <term><option>database</option></term>
 263               <listitem>
 264                 <para>The name is set based on entries in the udev's
 265                 Hardware Database with the key
 266                 <varname>ID_NET_NAME_FROM_DATABASE</varname>.
 267                 </para>
 268               </listitem>
 269             </varlistentry>
 270             <varlistentry>
 271               <term><option>onboard</option></term>
 272               <listitem>
 273                 <para>The name is set based on information given by
 274                 the firmware for on-board devices, as exported by the
 275                 udev property <varname>ID_NET_NAME_ONBOARD</varname>.
 276                 </para>
 277               </listitem>
 278             </varlistentry>
 279             <varlistentry>
 280               <term><option>slot</option></term>
 281               <listitem>
 282                 <para>The name is set based on information given by
 283                 the firmware for hot-plug devices, as exported by the
 284                 udev property <varname>ID_NET_NAME_SLOT</varname>.
 285                 </para>
 286               </listitem>
 287             </varlistentry>
 288             <varlistentry>
 289               <term><option>path</option></term>
 290               <listitem>
 291                 <para>The name is set based on the device's physical
 292                 location, as exported by the udev property
 293                 <varname>ID_NET_NAME_PATH</varname>.</para>
 294               </listitem>
 295             </varlistentry>
 296             <varlistentry>
 297               <term><option>mac</option></term>
 298               <listitem>
 299                 <para>The name is set based on the device's persistent
 300                 MAC address, as exported by the udev property
 301                 <varname>ID_NET_NAME_MAC</varname>.</para>
 302               </listitem>
 303             </varlistentry>
 304             <varlistentry>
 305               <term><option>keep</option></term>
 306               <listitem>
 307                 <para>If the device already had a name given by userspace (as part of creation of the device
 308                 or a rename), keep it.</para>
 309               </listitem>
 310             </varlistentry>
 311           </variablelist>
 312         </listitem>
 313       </varlistentry>
 314       <varlistentry>
 315         <term><varname>Name=</varname></term>
 316         <listitem>
 317           <para>The interface name to use. This option has lower precedence than
 318           <varname>NamePolicy=</varname>, so for this setting to take effect, <varname>NamePolicy=</varname>
 319           must either be unset, empty, disabled, or all policies configured there must fail. Also see the
 320           example below with <literal>Name=dmz0</literal>.</para>
 321
 322           <para>Note that specifying a name that the kernel might use for another
 323           interface (for example <literal>eth0</literal>) is dangerous because the
 324           name assignment done by udev will race with the assignment done by the
 325           kernel, and only one interface may use the name. Depending on the order of
 326           operations, either udev or the kernel will win, making the naming
 327           unpredictable. It is best to use some different prefix, for example
 328           <literal>internal0</literal>/<literal>external0</literal> or
 329           <literal>lan0</literal>/<literal>lan1</literal>/<literal>lan3</literal>.
 330           </para>
 331         </listitem>
 332       </varlistentry>
 333       <varlistentry>
 334         <term><varname>MTUBytes=</varname></term>
 335         <listitem>
 336           <para>The maximum transmission unit in bytes to set for the
 337           device. The usual suffixes K, M, G, are supported and are
 338           understood to the base of 1024.</para>
 339         </listitem>
 340       </varlistentry>
 341       <varlistentry>
 342         <term><varname>BitsPerSecond=</varname></term>
 343         <listitem>
 344           <para>The speed to set for the device, the value is rounded
 345           down to the nearest Mbps. The usual suffixes K, M, G, are
 346           supported and are understood to the base of 1000.</para>
 347         </listitem>
 348       </varlistentry>
 349       <varlistentry>
 350         <term><varname>Duplex=</varname></term>
 351         <listitem>
 352           <para>The duplex mode to set for the device. The accepted values are <option>half</option> and
 353           <option>full</option>.</para>
 354         </listitem>
 355       </varlistentry>
 356       <varlistentry>
 357         <term><varname>AutoNegotiation=</varname></term>
 358         <listitem>
 359           <para>Takes a boolean. If set to yes, automatic negotiation of transmission parameters is enabled.
 360           Autonegotiation is a procedure by which two connected ethernet devices choose
 361           common transmission parameters, such as speed, duplex mode, and flow control.
 362           When unset, the kernel's default will be used.</para>
 363
 364           <para>Note that if autonegotiation is enabled, speed and duplex settings are
 365           read-only. If autonegotation is disabled, speed and duplex settings are writable
 366           if the driver supports multiple link modes.</para>
 367         </listitem>
 368       </varlistentry>
 369       <varlistentry>
 370         <term><varname>WakeOnLan=</varname></term>
 371         <listitem>
 372           <para>The Wake-on-LAN policy to set for the device. The
 373           supported values are:</para>
 374
 375           <variablelist>
 376             <varlistentry>
 377               <term><option>phy</option></term>
 378               <listitem>
 379                 <para>Wake on PHY activity.</para>
 380               </listitem>
 381             </varlistentry>
 382             <varlistentry>
 383               <term><option>unicast</option></term>
 384               <listitem>
 385                 <para>Wake on unicast messages.</para>
 386               </listitem>
 387             </varlistentry>
 388             <varlistentry>
 389               <term><option>multicast</option></term>
 390               <listitem>
 391                 <para>Wake on multicast messages.</para>
 392               </listitem>
 393             </varlistentry>
 394             <varlistentry>
 395               <term><option>broadcast</option></term>
 396               <listitem>
 397                 <para>Wake on broadcast messages.</para>
 398               </listitem>
 399             </varlistentry>
 400             <varlistentry>
 401               <term><option>arp</option></term>
 402               <listitem>
 403                 <para>Wake on ARP.</para>
 404               </listitem>
 405             </varlistentry>
 406             <varlistentry>
 407               <term><option>magic</option></term>
 408               <listitem>
 409                 <para>Wake on receipt of a magic packet.
 410                 </para>
 411               </listitem>
 412             </varlistentry>
 413             <varlistentry>
 414               <term><option>secureon</option></term>
 415               <listitem>
 416                 <para>Enable secureon(tm) password for MagicPacket(tm).
 417                 </para>
 418               </listitem>
 419             </varlistentry>
 420             <varlistentry>
 421               <term><option>off</option></term>
 422               <listitem>
 423                 <para>Never wake.</para>
 424               </listitem>
 425             </varlistentry>
 426           </variablelist>
 427
 428           <para>Defaults to <option>off</option>.</para>
 429         </listitem>
 430       </varlistentry>
 431       <varlistentry>
 432         <term><varname>Port=</varname></term>
 433         <listitem>
 434           <para>The port option is used to select the device port. The
 435           supported values are:</para>
 436
 437           <variablelist>
 438             <varlistentry>
 439               <term><option>tp</option></term>
 440               <listitem>
 441                 <para>An Ethernet interface using Twisted-Pair cable as the medium.</para>
 442               </listitem>
 443             </varlistentry>
 444             <varlistentry>
 445               <term><option>aui</option></term>
 446               <listitem>
 447                 <para>Attachment Unit Interface (AUI). Normally used with hubs.
 448                 </para>
 449               </listitem>
 450             </varlistentry>
 451             <varlistentry>
 452               <term><option>bnc</option></term>
 453               <listitem>
 454                 <para>An Ethernet interface using BNC connectors and co-axial cable.</para>
 455               </listitem>
 456             </varlistentry>
 457             <varlistentry>
 458               <term><option>mii</option></term>
 459               <listitem>
 460                 <para>An Ethernet interface using a Media Independent Interface (MII).</para>
 461               </listitem>
 462             </varlistentry>
 463             <varlistentry>
 464               <term><option>fibre</option></term>
 465               <listitem>
 466                 <para>An Ethernet interface using Optical Fibre as the medium.</para>
 467               </listitem>
 468             </varlistentry>
 469           </variablelist>
 470         </listitem>
 471       </varlistentry>
 472       <varlistentry>
 473         <term><varname>Advertise=</varname></term>
 474         <listitem>
 475           <para>This sets what speeds and duplex modes of operation are advertised for auto-negotiation.
 476           This implies <literal>AutoNegotiation=yes</literal>. The supported values are:
 477
 478           <table>
 479             <title>Supported advertise values</title>
 480             <tgroup cols='3'>
 481               <colspec colname='Advertise' />
 482               <colspec colname='Speed' />
 483               <colspec colname='Duplex Mode' />
 484
 485               <thead><row>
 486                 <entry>Advertise</entry>
 487                 <entry>Speed (Mbps)</entry>
 488                 <entry>Duplex Mode</entry>
 489               </row></thead>
 490               <tbody>
 491                 <row><entry><option>10baset-half</option></entry>
 492                 <entry>10</entry><entry>half</entry></row>
 493
 494                 <row><entry><option>10baset-full</option></entry>
 495                 <entry>10</entry><entry>full</entry></row>
 496
 497                 <row><entry><option>100baset-half</option></entry>
 498                 <entry>100</entry><entry>half</entry></row>
 499
 500                 <row><entry><option>100baset-full</option></entry>
 501                 <entry>100</entry><entry>full</entry></row>
 502
 503                 <row><entry><option>1000baset-half</option></entry>
 504                 <entry>1000</entry><entry>half</entry></row>
 505
 506                 <row><entry><option>1000baset-full</option></entry>
 507                 <entry>1000</entry><entry>full</entry></row>
 508
 509                 <row><entry><option>10000baset-full</option></entry>
 510                 <entry>10000</entry><entry>full</entry></row>
 511
 512                 <row><entry><option>2500basex-full</option></entry>
 513                 <entry>2500</entry><entry>full</entry></row>
 514
 515                 <row><entry><option>1000basekx-full</option></entry>
 516                 <entry>1000</entry><entry>full</entry></row>
 517
 518                 <row><entry><option>10000basekx4-full</option></entry>
 519                 <entry>10000</entry><entry>full</entry></row>
 520
 521                 <row><entry><option>10000basekr-full</option></entry>
 522                 <entry>10000</entry><entry>full</entry></row>
 523
 524                 <row><entry><option>10000baser-fec</option></entry>
 525                 <entry>10000</entry><entry>full</entry></row>
 526
 527                 <row><entry><option>20000basemld2-full</option></entry>
 528                 <entry>20000</entry><entry>full</entry></row>
 529
 530                 <row><entry><option>20000basekr2-full</option></entry>
 531                 <entry>20000</entry><entry>full</entry></row>
 532               </tbody>
 533             </tgroup>
 534           </table>
 535
 536           By default this is unset, i.e. all possible modes will be advertised.
 537           This option may be specified more than once, in which case all specified speeds and modes are advertised.
 538           If the empty string is assigned to this option, the list is reset, and all prior assignments have no effect.
 539           </para>
 540         </listitem>
 541       </varlistentry>
 542       <varlistentry>
 543         <term><varname>TCPSegmentationOffload=</varname></term>
 544         <listitem>
 545           <para>Takes a boolean. If set to true, the TCP Segmentation Offload (TSO) is enabled.
 546           When unset, the kernel's default will be used.</para>
 547         </listitem>
 548       </varlistentry>
 549        <varlistentry>
 550       <term><varname>TCP6SegmentationOffload=</varname></term>
 551         <listitem>
 552           <para>Takes a boolean. If set to true, the TCP6 Segmentation Offload (tx-tcp6-segmentation) is enabled.
 553           When unset, the kernel's default will be used.</para>
 554         </listitem>
 555       </varlistentry>
 556       <varlistentry>
 557         <term><varname>GenericSegmentationOffload=</varname></term>
 558         <listitem>
 559           <para>Takes a boolean. If set to true, the Generic Segmentation Offload (GSO) is enabled.
 560           When unset, the kernel's default will be used.</para>
 561         </listitem>
 562       </varlistentry>
 563     <varlistentry>
 564         <term><varname>GenericReceiveOffload=</varname></term>
 565         <listitem>
 566           <para>Takes a boolean. If set to true, the Generic Receive Offload (GRO) is enabled.
 567           When unset, the kernel's default will be used.</para>
 568         </listitem>
 569       </varlistentry>
 570       <varlistentry>
 571         <term><varname>LargeReceiveOffload=</varname></term>
 572         <listitem>
 573           <para>Takes a boolean. If set to true, the Large Receive Offload (LRO) is enabled.
 574           When unset, the kernel's default will be used.</para>
 575         </listitem>
 576       </varlistentry>
 577       <varlistentry>
 578         <term><varname>RxChannels=</varname></term>
 579         <listitem>
 580           <para>Sets the number of receive channels (a number between 1 and 4294967295) .</para>
 581         </listitem>
 582       </varlistentry>
 583       <varlistentry>
 584         <term><varname>TxChannels=</varname></term>
 585         <listitem>
 586           <para>Sets the number of transmit channels (a number between 1 and 4294967295).</para>
 587         </listitem>
 588       </varlistentry>
 589       <varlistentry>
 590         <term><varname>OtherChannels=</varname></term>
 591         <listitem>
 592           <para>Sets the number of other channels (a number between 1 and 4294967295).</para>
 593         </listitem>
 594       </varlistentry>
 595       <varlistentry>
 596         <term><varname>CombinedChannels=</varname></term>
 597         <listitem>
 598           <para>Sets the number of combined set channels (a number between 1 and 4294967295).</para>
 599         </listitem>
 600       </varlistentry>
 601     </variablelist>
 602   </refsect1>
 603
 604   <refsect1>
 605     <title>Examples</title>
 606
 607     <example>
 608       <title>/usr/lib/systemd/network/99-default.link</title>
 609
 610       <para>The link file <filename>99-default.link</filename> that is
 611       shipped with systemd defines the default naming policy for
 612       links.</para>
 613
 614       <programlisting>[Link]
 615 NamePolicy=kernel database onboard slot path
 616 MACAddressPolicy=persistent</programlisting>
 617     </example>
 618
 619     <example>
 620       <title>/etc/systemd/network/10-dmz.link</title>
 621
 622       <para>This example assigns the fixed name <literal>dmz0</literal> to the interface with the MAC address
 623       00:a0:de:63:7a:e6:</para>
 624
 625       <programlisting>[Match]
 626 MACAddress=00:a0:de:63:7a:e6
 627
 628 [Link]
 629 Name=dmz0</programlisting>
 630
 631       <para><varname>NamePolicy=</varname> is not set, so <varname>Name=</varname> takes effect.
 632       We use the <literal>10-</literal> prefix to order this file early in the list. Note that it
 633       needs to before <literal>10-</literal>, i.e. it needs a numerical prefix, to have any effect
 634       at all.</para>
 635     </example>
 636
 637     <example>
 638       <title>/etc/systemd/network/10-internet.link</title>
 639
 640       <para>This example assigns the fixed name
 641       <literal>internet0</literal> to the interface with the device
 642       path <literal>pci-0000:00:1a.0-*</literal>:</para>
 643
 644       <programlisting>[Match]
 645 Path=pci-0000:00:1a.0-*
 646
 647 [Link]
 648 Name=internet0</programlisting>
 649     </example>
 650
 651     <example>
 652       <title>/etc/systemd/network/25-wireless.link</title>
 653
 654       <para>Here's an overly complex example that shows the use of a large number of [Match] and [Link] settings.</para>
 655
 656       <programlisting>[Match]
 657 MACAddress=12:34:56:78:9a:bc
 658 Driver=brcmsmac
 659 Path=pci-0000:02:00.0-*
 660 Type=wlan
 661 Virtualization=no
 662 Host=my-laptop
 663 Architecture=x86-64
 664
 665 [Link]
 666 Name=wireless0
 667 MTUBytes=1450
 668 BitsPerSecond=10M
 669 WakeOnLan=magic
 670 MACAddress=cb:a9:87:65:43:21</programlisting>
 671     </example>
 672   </refsect1>
 673
 674   <refsect1>
 675     <title>See Also</title>
 676     <para>
 677       <citerefentry>
 678         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 679       </citerefentry>,
 680       <citerefentry>
 681         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 682       </citerefentry>,
 683       <citerefentry>
 684         <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 685       </citerefentry>,
 686       <citerefentry>
 687         <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 688       </citerefentry>
 689     </para>
 690   </refsect1>
 691
 692 </refentry>