man/systemd.link.xml

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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>A plain ini-style text file that encodes configuration for matching network devices, used by
  30     <citerefentry><refentrytitle>systemd-udevd</refentrytitle><manvolnum>8</manvolnum></citerefentry> and in
  31     particular its <command>net_setup_link</command> builtin. See
  32     <citerefentry><refentrytitle>systemd.syntax</refentrytitle><manvolnum>7</manvolnum></citerefentry> for a
  33     general description of the syntax.</para>
  34
  35     <para>The link files are read from the files located in the system
  36     network directory <filename>/usr/lib/systemd/network</filename>,
  37     the volatile runtime network directory
  38     <filename>/run/systemd/network</filename>, and the local
  39     administration network directory
  40     <filename>/etc/systemd/network</filename>. Link files must have
  41     the extension <filename>.link</filename>; other extensions are
  42     ignored. All link files are collectively sorted and processed in
  43     lexical order, regardless of the directories in which they live.
  44     However, files with identical filenames replace each other. Files
  45     in <filename>/etc</filename> have the highest priority, files in
  46     <filename>/run</filename> take precedence over files with the same
  47     name in <filename>/usr/lib</filename>. This can be used to
  48     override a system-supplied link file with a local file if needed.
  49     As a special case, an empty file (file size 0) or symlink with the
  50     same name pointing to <filename>/dev/null</filename> disables the
  51     configuration file entirely (it is "masked").</para>
  52
  53     <para>The link file contains a [Match] section, which determines if a given link file may be applied to a
  54     given device, as well as a [Link] section specifying how the device should be configured. The first (in
  55     lexical order) of the link files that matches a given device is applied. Note that a default file
  56     <filename>99-default.link</filename> is shipped by the system. Any user-supplied
  57     <filename>.link</filename> should hence have a lexically earlier name to be considered at all.</para>
  58
  59     <para>See <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry> for
  60     diagnosing problems with <filename>.link</filename> files.</para>
  61   </refsect1>
  62
  63   <refsect1>
  64     <title>[Match] Section Options</title>
  65
  66     <para>A link file is said to match a device if all matches specified by the
  67     [Match] section are satisfied. When a link file does not contain valid settings
  68     in [Match] section, then the file will match all devices and
  69     <command>systemd-udevd</command> warns about that. Hint: to avoid the warning and to make it clear
  70     that all interfaces shall be matched, add the following:
  71     <programlisting>OriginalName=*</programlisting>
  72     The following keys are accepted:</para>
  73
  74     <variablelist class='network-directives'>
  75       <!-- This list is reused in systemd.network(3), hence maintain a specific order:
  76            1. device matches shared between the two lists
  77            2. non-shared settings
  78            3. host matches shared between the two lists
  79         -->
  80
  81       <varlistentry id='mac-address'>
  82         <term><varname>MACAddress=</varname></term>
  83         <listitem>
  84           <para>A whitespace-separated list of hardware addresses. Use full colon-, hyphen- or dot-delimited hexadecimal. See the example below.
  85           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
  86           of hardware addresses defined prior to this is reset.</para>
  87
  88           <para>Example:
  89           <programlisting>MACAddress=01:23:45:67:89:ab 00-11-22-33-44-55 AABB.CCDD.EEFF</programlisting></para>
  90         </listitem>
  91       </varlistentry>
  92
  93       <varlistentry id='permanent-mac-address'>
  94         <term><varname>PermanentMACAddress=</varname></term>
  95         <listitem>
  96           <para>A whitespace-separated list of hardware's permanent addresses. While
  97           <varname>MACAddress=</varname> matches the device's current MAC address, this matches the
  98           device's permanent MAC address, which may be different from the current one. Use full
  99           colon-, hyphen- or dot-delimited hexadecimal. This option may appear more than once, in
 100           which case the lists are merged. If the empty string is assigned to this option, the list
 101           of hardware addresses defined prior to this is reset.</para>
 102         </listitem>
 103       </varlistentry>
 104
 105       <varlistentry id='path'>
 106         <term><varname>Path=</varname></term>
 107         <listitem>
 108           <para>A whitespace-separated list of shell-style globs matching
 109           the persistent path, as exposed by the udev property
 110           <varname>ID_PATH</varname>.</para>
 111         </listitem>
 112       </varlistentry>
 113
 114       <varlistentry id='driver'>
 115         <term><varname>Driver=</varname></term>
 116         <listitem>
 117           <para>A whitespace-separated list of shell-style globs matching the driver currently bound to the
 118           device, as exposed by the udev property <varname>ID_NET_DRIVER</varname> of its parent device, or
 119           if that is not set, the driver as exposed by <command>ethtool -i</command> of the device itself.
 120           If the list is prefixed with a "!", the test is inverted.</para>
 121         </listitem>
 122       </varlistentry>
 123
 124       <varlistentry id='type'>
 125         <term><varname>Type=</varname></term>
 126         <listitem>
 127           <para>A whitespace-separated list of shell-style globs matching the device type, as exposed by
 128           <command>networkctl status</command>. If the list is prefixed with a "!", the test is inverted.
 129           </para>
 130         </listitem>
 131       </varlistentry>
 132
 133       <varlistentry id='property'>
 134         <term><varname>Property=</varname></term>
 135         <listitem>
 136           <para>A whitespace-separated list of udev property name with its value after a equal
 137           (<literal>=</literal>). If multiple properties are specified, the test results are ANDed.
 138           If the list is prefixed with a "!", the test is inverted. If a value contains white
 139           spaces, then please quote whole key and value pair. If a value contains quotation, then
 140           please escape the quotation with <literal>\</literal>.</para>
 141
 142           <para>Example: if a .link file has the following:
 143           <programlisting>Property=ID_MODEL_ID=9999 "ID_VENDOR_FROM_DATABASE=vendor name" "KEY=with \"quotation\""</programlisting>
 144           then, the .link file matches only when an interface has all the above three properties.
 145           </para>
 146         </listitem>
 147       </varlistentry>
 148
 149       <varlistentry>
 150         <term><varname>OriginalName=</varname></term>
 151         <listitem>
 152           <para>A whitespace-separated list of shell-style globs matching the device name, as exposed by the
 153           udev property "INTERFACE". This cannot be used to match on names that have already been changed
 154           from userspace. Caution is advised when matching on kernel-assigned names, as they are known to be
 155           unstable between reboots.</para>
 156         </listitem>
 157       </varlistentry>
 158
 159       <varlistentry id='host'>
 160         <term><varname>Host=</varname></term>
 161         <listitem>
 162           <para>Matches against the hostname or machine ID of the host. See <varname>ConditionHost=</varname> in
 163           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 164           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 165           If an empty string is assigned, then previously assigned value is cleared.
 166           </para>
 167         </listitem>
 168       </varlistentry>
 169
 170       <varlistentry id='virtualization'>
 171         <term><varname>Virtualization=</varname></term>
 172         <listitem>
 173           <para>Checks whether the system is executed in a virtualized environment and optionally test
 174           whether it is a specific implementation. See <varname>ConditionVirtualization=</varname> in
 175           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 176           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 177           If an empty string is assigned, then previously assigned value is cleared.
 178           </para>
 179         </listitem>
 180       </varlistentry>
 181
 182       <varlistentry id='kernel-command-line'>
 183         <term><varname>KernelCommandLine=</varname></term>
 184         <listitem>
 185           <para>Checks whether a specific kernel command line option is set. See
 186           <varname>ConditionKernelCommandLine=</varname> in
 187           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 188           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 189           If an empty string is assigned, then previously assigned value is cleared.
 190           </para>
 191         </listitem>
 192       </varlistentry>
 193
 194       <varlistentry id='kernel-version'>
 195         <term><varname>KernelVersion=</varname></term>
 196         <listitem>
 197           <para>Checks whether the kernel version (as reported by <command>uname -r</command>) matches a certain
 198           expression. See <varname>ConditionKernelVersion=</varname> in
 199           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 200           details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 201           If an empty string is assigned, then previously assigned value is cleared.
 202           </para>
 203         </listitem>
 204       </varlistentry>
 205
 206       <varlistentry id='architecture'>
 207         <term><varname>Architecture=</varname></term>
 208         <listitem>
 209           <para>Checks whether the system is running on a specific architecture. See
 210           <varname>ConditionArchitecture=</varname> in
 211           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 212           for details. When prefixed with an exclamation mark (<literal>!</literal>), the result is negated.
 213           If an empty string is assigned, then previously assigned value is cleared.
 214           </para>
 215         </listitem>
 216       </varlistentry>
 217     </variablelist>
 218
 219   </refsect1>
 220
 221   <refsect1>
 222     <title>[Link] Section Options</title>
 223
 224     <para>The [Link] section accepts the following
 225     keys:</para>
 226
 227     <variablelist class='network-directives'>
 228       <varlistentry>
 229         <term><varname>Description=</varname></term>
 230         <listitem>
 231           <para>A description of the device.</para>
 232         </listitem>
 233       </varlistentry>
 234       <varlistentry>
 235         <term><varname>Alias=</varname></term>
 236         <listitem>
 237           <para>The <varname>ifalias</varname> interface property is set to this value.</para>
 238         </listitem>
 239       </varlistentry>
 240       <varlistentry>
 241         <term><varname>MACAddressPolicy=</varname></term>
 242         <listitem>
 243           <para>The policy by which the MAC address should be set. The
 244           available policies are:
 245           </para>
 246
 247           <variablelist>
 248             <varlistentry>
 249               <term><option>persistent</option></term>
 250               <listitem>
 251                 <para>If the hardware has a persistent MAC address, as
 252                 most hardware should, and if it is used by the kernel,
 253                 nothing is done. Otherwise, a new MAC address is
 254                 generated which is guaranteed to be the same on every
 255                 boot for the given machine and the given device, but
 256                 which is otherwise random. This feature depends on ID_NET_NAME_*
 257                 properties to exist for the link. On hardware where these
 258                 properties are not set, the generation of a persistent MAC address
 259                 will fail.</para>
 260               </listitem>
 261             </varlistentry>
 262             <varlistentry>
 263               <term><option>random</option></term>
 264               <listitem>
 265                 <para>If the kernel is using a random MAC address,
 266                 nothing is done. Otherwise, a new address is randomly
 267                 generated each time the device appears, typically at
 268                 boot. Either way, the random address will have the
 269                 <literal>unicast</literal> and
 270                 <literal>locally administered</literal> bits set.</para>
 271               </listitem>
 272             </varlistentry>
 273             <varlistentry>
 274               <term><option>none</option></term>
 275               <listitem>
 276                 <para>Keeps the MAC address assigned by the kernel.</para>
 277               </listitem>
 278             </varlistentry>
 279           </variablelist>
 280         </listitem>
 281       </varlistentry>
 282       <varlistentry>
 283         <term><varname>MACAddress=</varname></term>
 284         <listitem>
 285           <para>The MAC address to use, if no
 286           <varname>MACAddressPolicy=</varname>
 287           is specified.</para>
 288         </listitem>
 289       </varlistentry>
 290       <varlistentry>
 291         <term><varname>NamePolicy=</varname></term>
 292         <listitem>
 293           <para>An ordered, space-separated list of policies by which the interface name should be set.
 294           <varname>NamePolicy=</varname> may be disabled by specifying <option>net.ifnames=0</option> on the
 295           kernel command line. Each of the policies may fail, and the first successful one is used. The name
 296           is not set directly, but is exported to udev as the property <option>ID_NET_NAME</option>, which
 297           is, by default, used by a
 298           <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 299           rule to set <varname>NAME</varname>. The available policies are:
 300           </para>
 301
 302           <variablelist>
 303             <varlistentry>
 304               <term><option>kernel</option></term>
 305               <listitem>
 306                 <para>If the kernel claims that the name it has set
 307                 for a device is predictable, then no renaming is
 308                 performed.</para>
 309               </listitem>
 310             </varlistentry>
 311             <varlistentry>
 312               <term><option>database</option></term>
 313               <listitem>
 314                 <para>The name is set based on entries in the udev's
 315                 Hardware Database with the key
 316                 <varname>ID_NET_NAME_FROM_DATABASE</varname>.
 317                 </para>
 318               </listitem>
 319             </varlistentry>
 320             <varlistentry>
 321               <term><option>onboard</option></term>
 322               <listitem>
 323                 <para>The name is set based on information given by
 324                 the firmware for on-board devices, as exported by the
 325                 udev property <varname>ID_NET_NAME_ONBOARD</varname>.
 326                 See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
 327                 </para>
 328               </listitem>
 329             </varlistentry>
 330             <varlistentry>
 331               <term><option>slot</option></term>
 332               <listitem>
 333                 <para>The name is set based on information given by
 334                 the firmware for hot-plug devices, as exported by the
 335                 udev property <varname>ID_NET_NAME_SLOT</varname>.
 336                 See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
 337                 </para>
 338               </listitem>
 339             </varlistentry>
 340             <varlistentry>
 341               <term><option>path</option></term>
 342               <listitem>
 343                 <para>The name is set based on the device's physical
 344                 location, as exported by the udev property
 345                 <varname>ID_NET_NAME_PATH</varname>.
 346                 See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
 347                 </para>
 348               </listitem>
 349             </varlistentry>
 350             <varlistentry>
 351               <term><option>mac</option></term>
 352               <listitem>
 353                 <para>The name is set based on the device's persistent
 354                 MAC address, as exported by the udev property
 355                 <varname>ID_NET_NAME_MAC</varname>.
 356                 See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
 357                 </para>
 358               </listitem>
 359             </varlistentry>
 360             <varlistentry>
 361               <term><option>keep</option></term>
 362               <listitem>
 363                 <para>If the device already had a name given by userspace (as part of creation of the device
 364                 or a rename), keep it.</para>
 365               </listitem>
 366             </varlistentry>
 367           </variablelist>
 368         </listitem>
 369       </varlistentry>
 370       <varlistentry>
 371         <term><varname>Name=</varname></term>
 372         <listitem>
 373           <para>The interface name to use. This option has lower precedence than
 374           <varname>NamePolicy=</varname>, so for this setting to take effect, <varname>NamePolicy=</varname>
 375           must either be unset, empty, disabled, or all policies configured there must fail. Also see the
 376           example below with <literal>Name=dmz0</literal>.</para>
 377
 378           <para>Note that specifying a name that the kernel might use for another
 379           interface (for example <literal>eth0</literal>) is dangerous because the
 380           name assignment done by udev will race with the assignment done by the
 381           kernel, and only one interface may use the name. Depending on the order of
 382           operations, either udev or the kernel will win, making the naming
 383           unpredictable. It is best to use some different prefix, for example
 384           <literal>internal0</literal>/<literal>external0</literal> or
 385           <literal>lan0</literal>/<literal>lan1</literal>/<literal>lan3</literal>.
 386           </para>
 387         </listitem>
 388       </varlistentry>
 389       <varlistentry>
 390         <term><varname>AlternativeNamesPolicy=</varname></term>
 391         <listitem>
 392           <para>A space-separated list of policies by which the interface's alternative names
 393           should be set. Each of the policies may fail, and all successful policies are used. The
 394           available policies are <literal>database</literal>, <literal>onboard</literal>,
 395           <literal>slot</literal>, <literal>path</literal>, and <literal>mac</literal>. If the
 396           kernel does not support the alternative names, then this setting will be ignored.
 397           </para>
 398         </listitem>
 399       </varlistentry>
 400       <varlistentry>
 401         <term><varname>AlternativeName=</varname></term>
 402         <listitem>
 403           <para>The alternative interface name to use. This option can be specified multiple times.
 404           If the empty string is assigned to this option, the list is reset, and all prior assignments
 405           have no effect. If the kernel does not support the alternative names, then this setting will
 406           be ignored.</para>
 407         </listitem>
 408       </varlistentry>
 409       <varlistentry>
 410         <term><varname>MTUBytes=</varname></term>
 411         <listitem>
 412           <para>The maximum transmission unit in bytes to set for the
 413           device. The usual suffixes K, M, G, are supported and are
 414           understood to the base of 1024.</para>
 415         </listitem>
 416       </varlistentry>
 417       <varlistentry>
 418         <term><varname>BitsPerSecond=</varname></term>
 419         <listitem>
 420           <para>The speed to set for the device, the value is rounded
 421           down to the nearest Mbps. The usual suffixes K, M, G, are
 422           supported and are understood to the base of 1000.</para>
 423         </listitem>
 424       </varlistentry>
 425       <varlistentry>
 426         <term><varname>Duplex=</varname></term>
 427         <listitem>
 428           <para>The duplex mode to set for the device. The accepted values are <option>half</option> and
 429           <option>full</option>.</para>
 430         </listitem>
 431       </varlistentry>
 432       <varlistentry>
 433         <term><varname>AutoNegotiation=</varname></term>
 434         <listitem>
 435           <para>Takes a boolean. If set to yes, automatic negotiation of transmission parameters is enabled.
 436           Autonegotiation is a procedure by which two connected ethernet devices choose
 437           common transmission parameters, such as speed, duplex mode, and flow control.
 438           When unset, the kernel's default will be used.</para>
 439
 440           <para>Note that if autonegotiation is enabled, speed and duplex settings are
 441           read-only. If autonegotiation is disabled, speed and duplex settings are writable
 442           if the driver supports multiple link modes.</para>
 443         </listitem>
 444       </varlistentry>
 445       <varlistentry>
 446         <term><varname>WakeOnLan=</varname></term>
 447         <listitem>
 448           <para>The Wake-on-LAN policy to set for the device. The
 449           supported values are:</para>
 450
 451           <variablelist>
 452             <varlistentry>
 453               <term><option>phy</option></term>
 454               <listitem>
 455                 <para>Wake on PHY activity.</para>
 456               </listitem>
 457             </varlistentry>
 458             <varlistentry>
 459               <term><option>unicast</option></term>
 460               <listitem>
 461                 <para>Wake on unicast messages.</para>
 462               </listitem>
 463             </varlistentry>
 464             <varlistentry>
 465               <term><option>multicast</option></term>
 466               <listitem>
 467                 <para>Wake on multicast messages.</para>
 468               </listitem>
 469             </varlistentry>
 470             <varlistentry>
 471               <term><option>broadcast</option></term>
 472               <listitem>
 473                 <para>Wake on broadcast messages.</para>
 474               </listitem>
 475             </varlistentry>
 476             <varlistentry>
 477               <term><option>arp</option></term>
 478               <listitem>
 479                 <para>Wake on ARP.</para>
 480               </listitem>
 481             </varlistentry>
 482             <varlistentry>
 483               <term><option>magic</option></term>
 484               <listitem>
 485                 <para>Wake on receipt of a magic packet.
 486                 </para>
 487               </listitem>
 488             </varlistentry>
 489             <varlistentry>
 490               <term><option>secureon</option></term>
 491               <listitem>
 492                 <para>Enable secureon(tm) password for MagicPacket(tm).
 493                 </para>
 494               </listitem>
 495             </varlistentry>
 496             <varlistentry>
 497               <term><option>off</option></term>
 498               <listitem>
 499                 <para>Never wake.</para>
 500               </listitem>
 501             </varlistentry>
 502           </variablelist>
 503
 504           <para>Defaults to <option>off</option>.</para>
 505         </listitem>
 506       </varlistentry>
 507       <varlistentry>
 508         <term><varname>Port=</varname></term>
 509         <listitem>
 510           <para>The port option is used to select the device port. The
 511           supported values are:</para>
 512
 513           <variablelist>
 514             <varlistentry>
 515               <term><option>tp</option></term>
 516               <listitem>
 517                 <para>An Ethernet interface using Twisted-Pair cable as the medium.</para>
 518               </listitem>
 519             </varlistentry>
 520             <varlistentry>
 521               <term><option>aui</option></term>
 522               <listitem>
 523                 <para>Attachment Unit Interface (AUI). Normally used with hubs.
 524                 </para>
 525               </listitem>
 526             </varlistentry>
 527             <varlistentry>
 528               <term><option>bnc</option></term>
 529               <listitem>
 530                 <para>An Ethernet interface using BNC connectors and co-axial cable.</para>
 531               </listitem>
 532             </varlistentry>
 533             <varlistentry>
 534               <term><option>mii</option></term>
 535               <listitem>
 536                 <para>An Ethernet interface using a Media Independent Interface (MII).</para>
 537               </listitem>
 538             </varlistentry>
 539             <varlistentry>
 540               <term><option>fibre</option></term>
 541               <listitem>
 542                 <para>An Ethernet interface using Optical Fibre as the medium.</para>
 543               </listitem>
 544             </varlistentry>
 545           </variablelist>
 546         </listitem>
 547       </varlistentry>
 548       <varlistentry>
 549         <term><varname>Advertise=</varname></term>
 550         <listitem>
 551           <para>This sets what speeds and duplex modes of operation are advertised for auto-negotiation.
 552           This implies <literal>AutoNegotiation=yes</literal>. The supported values are:
 553
 554           <table>
 555             <title>Supported advertise values</title>
 556             <tgroup cols='3'>
 557               <colspec colname='Advertise' />
 558               <colspec colname='Speed' />
 559               <colspec colname='Duplex Mode' />
 560
 561               <thead><row>
 562                 <entry>Advertise</entry>
 563                 <entry>Speed (Mbps)</entry>
 564                 <entry>Duplex Mode</entry>
 565               </row></thead>
 566               <tbody>
 567                 <row><entry><option>10baset-half</option></entry>
 568                 <entry>10</entry><entry>half</entry></row>
 569
 570                 <row><entry><option>10baset-full</option></entry>
 571                 <entry>10</entry><entry>full</entry></row>
 572
 573                 <row><entry><option>100baset-half</option></entry>
 574                 <entry>100</entry><entry>half</entry></row>
 575
 576                 <row><entry><option>100baset-full</option></entry>
 577                 <entry>100</entry><entry>full</entry></row>
 578
 579                 <row><entry><option>1000baset-half</option></entry>
 580                 <entry>1000</entry><entry>half</entry></row>
 581
 582                 <row><entry><option>1000baset-full</option></entry>
 583                 <entry>1000</entry><entry>full</entry></row>
 584
 585                 <row><entry><option>10000baset-full</option></entry>
 586                 <entry>10000</entry><entry>full</entry></row>
 587
 588                 <row><entry><option>2500basex-full</option></entry>
 589                 <entry>2500</entry><entry>full</entry></row>
 590
 591                 <row><entry><option>1000basekx-full</option></entry>
 592                 <entry>1000</entry><entry>full</entry></row>
 593
 594                 <row><entry><option>10000basekx4-full</option></entry>
 595                 <entry>10000</entry><entry>full</entry></row>
 596
 597                 <row><entry><option>10000basekr-full</option></entry>
 598                 <entry>10000</entry><entry>full</entry></row>
 599
 600                 <row><entry><option>10000baser-fec</option></entry>
 601                 <entry>10000</entry><entry>full</entry></row>
 602
 603                 <row><entry><option>20000basemld2-full</option></entry>
 604                 <entry>20000</entry><entry>full</entry></row>
 605
 606                 <row><entry><option>20000basekr2-full</option></entry>
 607                 <entry>20000</entry><entry>full</entry></row>
 608               </tbody>
 609             </tgroup>
 610           </table>
 611
 612           By default this is unset, i.e. all possible modes will be advertised.
 613           This option may be specified more than once, in which case all specified speeds and modes are advertised.
 614           If the empty string is assigned to this option, the list is reset, and all prior assignments have no effect.
 615           </para>
 616         </listitem>
 617       </varlistentry>
 618       <varlistentry>
 619         <term><varname>ReceiveChecksumOffload=</varname></term>
 620         <listitem>
 621           <para>Takes a boolean. If set to true, the hardware offload for checksumming of ingress
 622           network packets is enabled. When unset, the kernel's default will be used.</para>
 623         </listitem>
 624       </varlistentry>
 625       <varlistentry>
 626         <term><varname>TransmitChecksumOffload=</varname></term>
 627         <listitem>
 628           <para>Takes a boolean. If set to true, the hardware offload for checksumming of egress
 629           network packets is enabled. When unset, the kernel's default will be used.</para>
 630         </listitem>
 631       </varlistentry>
 632       <varlistentry>
 633         <term><varname>TCPSegmentationOffload=</varname></term>
 634         <listitem>
 635           <para>Takes a boolean. If set to true, the TCP Segmentation Offload (TSO) is enabled.
 636           When unset, the kernel's default will be used.</para>
 637         </listitem>
 638       </varlistentry>
 639        <varlistentry>
 640       <term><varname>TCP6SegmentationOffload=</varname></term>
 641         <listitem>
 642           <para>Takes a boolean. If set to true, the TCP6 Segmentation Offload (tx-tcp6-segmentation) is enabled.
 643           When unset, the kernel's default will be used.</para>
 644         </listitem>
 645       </varlistentry>
 646       <varlistentry>
 647         <term><varname>GenericSegmentationOffload=</varname></term>
 648         <listitem>
 649           <para>Takes a boolean. If set to true, the Generic Segmentation Offload (GSO) is enabled.
 650           When unset, the kernel's default will be used.</para>
 651         </listitem>
 652       </varlistentry>
 653       <varlistentry>
 654         <term><varname>GenericReceiveOffload=</varname></term>
 655         <listitem>
 656           <para>Takes a boolean. If set to true, the Generic Receive Offload (GRO) is enabled.
 657           When unset, the kernel's default will be used.</para>
 658         </listitem>
 659       </varlistentry>
 660       <varlistentry>
 661         <term><varname>LargeReceiveOffload=</varname></term>
 662         <listitem>
 663           <para>Takes a boolean. If set to true, the Large Receive Offload (LRO) is enabled.
 664           When unset, the kernel's default will be used.</para>
 665         </listitem>
 666       </varlistentry>
 667       <varlistentry>
 668         <term><varname>RxChannels=</varname></term>
 669         <listitem>
 670           <para>Sets the number of receive channels (a number between 1 and 4294967295) .</para>
 671         </listitem>
 672       </varlistentry>
 673       <varlistentry>
 674         <term><varname>TxChannels=</varname></term>
 675         <listitem>
 676           <para>Sets the number of transmit channels (a number between 1 and 4294967295).</para>
 677         </listitem>
 678       </varlistentry>
 679       <varlistentry>
 680         <term><varname>OtherChannels=</varname></term>
 681         <listitem>
 682           <para>Sets the number of other channels (a number between 1 and 4294967295).</para>
 683         </listitem>
 684       </varlistentry>
 685       <varlistentry>
 686         <term><varname>CombinedChannels=</varname></term>
 687         <listitem>
 688           <para>Sets the number of combined set channels (a number between 1 and 4294967295).</para>
 689         </listitem>
 690       </varlistentry>
 691       <varlistentry>
 692         <term><varname>RxBufferSize=</varname></term>
 693         <listitem>
 694           <para>Takes an integer. Specifies the maximum number of pending packets in the NIC receive buffer.
 695           When unset, the kernel's default will be used.</para>
 696         </listitem>
 697       </varlistentry>
 698       <varlistentry>
 699         <term><varname>RxMiniBufferSize=</varname></term>
 700         <listitem>
 701           <para>Takes an integer. Specifies the maximum number of pending packets in the NIC mini receive buffer.
 702           When unset, the kernel's default will be used.</para>
 703         </listitem>
 704       </varlistentry>
 705       <varlistentry>
 706         <term><varname>RxJumboBufferSize=</varname></term>
 707         <listitem>
 708           <para>Takes an integer. Specifies the maximum number of pending packets in the NIC jumbo receive buffer.
 709           When unset, the kernel's default will be used.</para>
 710         </listitem>
 711       </varlistentry>
 712       <varlistentry>
 713         <term><varname>TxBufferSize=</varname></term>
 714         <listitem>
 715           <para>Takes an integer. Specifies the maximum number of pending packets in the NIC transmit buffer.
 716           When unset, the kernel's default will be used.</para>
 717         </listitem>
 718       </varlistentry>
 719       <varlistentry>
 720         <term><varname>RxFlowControl=</varname></term>
 721         <listitem>
 722           <para>Takes a boolean. When set, enables the receive flow control, also known as the ethernet
 723           receive PAUSE message (generate and send ethernet PAUSE frames). When unset, the kernel's
 724           default will be used.</para>
 725         </listitem>
 726       </varlistentry>
 727       <varlistentry>
 728         <term><varname>TxFlowControl=</varname></term>
 729         <listitem>
 730           <para>Takes a boolean. When set, enables the transmit flow control, also known as the ethernet
 731           transmit PAUSE message (respond to received ethernet PAUSE frames). When unset, the kernel's
 732           default will be used.</para>
 733         </listitem>
 734       </varlistentry>
 735       <varlistentry>
 736         <term><varname>AutoNegotiationFlowControl=</varname></term>
 737         <listitem>
 738           <para>Takes a boolean. When set, the auto negotiation enables the interface to exchange state
 739           advertisements with the connected peer so that the two devices can agree on the ethernet
 740           PAUSE configuration. When unset, the kernel's default will be used.</para>
 741         </listitem>
 742       </varlistentry>
 743
 744     </variablelist>
 745   </refsect1>
 746
 747   <refsect1>
 748     <title>Examples</title>
 749
 750     <example>
 751       <title>/usr/lib/systemd/network/99-default.link</title>
 752
 753       <para>The link file <filename>99-default.link</filename> that is
 754       shipped with systemd defines the default naming policy for
 755       links.</para>
 756
 757       <programlisting>[Link]
 758 NamePolicy=kernel database onboard slot path
 759 MACAddressPolicy=persistent</programlisting>
 760     </example>
 761
 762     <example>
 763       <title>/etc/systemd/network/10-dmz.link</title>
 764
 765       <para>This example assigns the fixed name <literal>dmz0</literal> to the interface with the MAC address
 766       00:a0:de:63:7a:e6:</para>
 767
 768       <programlisting>[Match]
 769 MACAddress=00:a0:de:63:7a:e6
 770
 771 [Link]
 772 Name=dmz0</programlisting>
 773
 774       <para><varname>NamePolicy=</varname> is not set, so <varname>Name=</varname> takes effect. We use the
 775       <literal>10-</literal> prefix to order this file early in the list. Note that it needs to be before
 776       <literal>99-link</literal>, i.e. it needs a numerical prefix, to have any effect at all.</para>
 777     </example>
 778
 779     <example>
 780       <title>Debugging <varname>NamePolicy=</varname> assignments</title>
 781
 782       <programlisting>$ sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/hub0
 783 …
 784 Parsed configuration file /usr/lib/systemd/network/99-default.link
 785 Parsed configuration file /etc/systemd/network/10-eth0.link
 786 ID_NET_DRIVER=cdc_ether
 787 Config file /etc/systemd/network/10-eth0.link applies to device hub0
 788 link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
 789 hub0: Device has name_assign_type=4
 790 Using default interface naming scheme 'v240'.
 791 hub0: Policies didn't yield a name, using specified Name=hub0.
 792 ID_NET_LINK_FILE=/etc/systemd/network/10-eth0.link
 793 ID_NET_NAME=hub0
 794 …</programlisting>
 795
 796      <para>Explicit <varname>Name=</varname> configuration wins in this case.</para>
 797
 798      <programlisting>sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/enp0s31f6
 799 …
 800 Parsed configuration file /usr/lib/systemd/network/99-default.link
 801 Parsed configuration file /etc/systemd/network/10-eth0.link
 802 Created link configuration context.
 803 ID_NET_DRIVER=e1000e
 804 Config file /usr/lib/systemd/network/99-default.link applies to device enp0s31f6
 805 link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
 806 enp0s31f6: Device has name_assign_type=4
 807 Using default interface naming scheme 'v240'.
 808 enp0s31f6: Policy *keep*: keeping existing userspace name
 809 enp0s31f6: Device has addr_assign_type=0
 810 enp0s31f6: MAC on the device already matches policy *persistent*
 811 ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
 812 …
 813 </programlisting>
 814
 815      <para>In this case, the interface was already renamed, so the <option>keep</option> policy specified as
 816      the first option in <filename index="false">99-default.link</filename> means that the existing name is
 817      preserved. If <option>keep</option> was removed, or if were in boot before the renaming has happened,
 818      we might get the following instead:</para>
 819
 820      <programlisting>enp0s31f6: Policy *path* yields "enp0s31f6".
 821 enp0s31f6: Device has addr_assign_type=0
 822 enp0s31f6: MAC on the device already matches policy *persistent*
 823 ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
 824 ID_NET_NAME=enp0s31f6
 825 …
 826 </programlisting>
 827
 828       <para>Please note that the details of output are subject to change.</para>
 829     </example>
 830
 831     <example>
 832       <title>/etc/systemd/network/10-internet.link</title>
 833
 834       <para>This example assigns the fixed name
 835       <literal>internet0</literal> to the interface with the device
 836       path <literal>pci-0000:00:1a.0-*</literal>:</para>
 837
 838       <programlisting>[Match]
 839 Path=pci-0000:00:1a.0-*
 840
 841 [Link]
 842 Name=internet0</programlisting>
 843     </example>
 844
 845     <example>
 846       <title>/etc/systemd/network/25-wireless.link</title>
 847
 848       <para>Here's an overly complex example that shows the use of a large number of [Match] and [Link] settings.</para>
 849
 850       <programlisting>[Match]
 851 MACAddress=12:34:56:78:9a:bc
 852 Driver=brcmsmac
 853 Path=pci-0000:02:00.0-*
 854 Type=wlan
 855 Virtualization=no
 856 Host=my-laptop
 857 Architecture=x86-64
 858
 859 [Link]
 860 Name=wireless0
 861 MTUBytes=1450
 862 BitsPerSecond=10M
 863 WakeOnLan=magic
 864 MACAddress=cb:a9:87:65:43:21</programlisting>
 865     </example>
 866   </refsect1>
 867
 868   <refsect1>
 869     <title>See Also</title>
 870     <para>
 871       <citerefentry>
 872         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 873       </citerefentry>,
 874       <citerefentry>
 875         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 876       </citerefentry>,
 877       <citerefentry>
 878         <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 879       </citerefentry>,
 880       <citerefentry>
 881         <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 882       </citerefentry>
 883     </para>
 884   </refsect1>
 885
 886 </refentry>