man/systemd.link.xml

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