man/systemd.link.xml

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   8   Copyright © 2014 Tom Gundersen
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  10
  11 <refentry id="systemd.link">
  12   <refentryinfo>
  13     <title>systemd.link</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>systemd.link</refentrytitle>
  19     <manvolnum>5</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>systemd.link</refname>
  24     <refpurpose>Network device configuration</refpurpose>
  25   </refnamediv>
  26
  27   <refsynopsisdiv>
  28     <para><filename><replaceable>link</replaceable>.link</filename></para>
  29   </refsynopsisdiv>
  30
  31   <refsect1>
  32     <title>Description</title>
  33
  34     <para>Network link configuration is performed by the
  35     <command>net_setup_link</command> udev builtin.</para>
  36
  37     <para>The link files are read from the files located in the system
  38     network directory <filename>/usr/lib/systemd/network</filename>,
  39     the volatile runtime network directory
  40     <filename>/run/systemd/network</filename>, and the local
  41     administration network directory
  42     <filename>/etc/systemd/network</filename>. Link files must have
  43     the extension <filename>.link</filename>; other extensions are
  44     ignored. All link files are collectively sorted and processed in
  45     lexical order, regardless of the directories in which they live.
  46     However, files with identical filenames replace each other. Files
  47     in <filename>/etc</filename> have the highest priority, files in
  48     <filename>/run</filename> take precedence over files with the same
  49     name in <filename>/usr/lib</filename>. This can be used to
  50     override a system-supplied link file with a local file if needed.
  51     As a special case, an empty file (file size 0) or symlink with the
  52     same name pointing to <filename>/dev/null</filename> disables the
  53     configuration file entirely (it is "masked").</para>
  54
  55     <para>The link file contains a <literal>[Match]</literal> section,
  56     which determines if a given link file may be applied to a given
  57     device, as well as a <literal>[Link]</literal> section specifying
  58     how the device should be configured. The first (in lexical order)
  59     of the link files that matches a given device is applied. Note
  60     that a default file <filename>99-default.link</filename> is
  61     shipped by the system. Any user-supplied
  62     <filename>.link</filename> should hence have a lexically earlier
  63     name to be considered at all.</para>
  64
  65     <para>See
  66     <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  67     for diagnosing problems with <filename>.link</filename> files.</para>
  68   </refsect1>
  69
  70   <refsect1>
  71     <title>[Match] Section Options</title>
  72
  73     <para>A link file is said to match a device if each of the entries
  74     in the <literal>[Match]</literal> section matches, or if the
  75     section is empty. The following keys are accepted:</para>
  76
  77     <variablelist class='network-directives'>
  78       <varlistentry>
  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       <varlistentry>
  90         <term><varname>OriginalName=</varname></term>
  91         <listitem>
  92           <para>A whitespace-separated list of shell-style globs matching
  93           the device name, as exposed by the udev property
  94           "INTERFACE". This cannot be used to match on names that have
  95           already been changed from userspace. Caution is advised when matching on
  96           kernel-assigned names, as they are known to be unstable
  97           between reboots.</para>
  98         </listitem>
  99       </varlistentry>
 100       <varlistentry>
 101         <term><varname>Path=</varname></term>
 102         <listitem>
 103           <para>A whitespace-separated list of shell-style globs matching
 104           the persistent path, as exposed by the udev property
 105           <literal>ID_PATH</literal>.</para>
 106         </listitem>
 107       </varlistentry>
 108       <varlistentry>
 109         <term><varname>Driver=</varname></term>
 110         <listitem>
 111           <para>A whitespace-separated list of shell-style globs matching
 112           the driver currently bound to the device,
 113           as exposed by the udev property <literal>DRIVER</literal>
 114           of its parent device, or if that is not set, the
 115           driver as exposed by <literal>ethtool -i</literal>
 116           of the device itself.</para>
 117         </listitem>
 118       </varlistentry>
 119       <varlistentry>
 120         <term><varname>Type=</varname></term>
 121         <listitem>
 122           <para>A whitespace-separated list of shell-style globs matching
 123           the device type, as exposed by the udev
 124           property <literal>DEVTYPE</literal>.</para>
 125         </listitem>
 126       </varlistentry>
 127       <varlistentry>
 128         <term><varname>Host=</varname></term>
 129         <listitem>
 130           <para>Matches against the hostname or machine
 131           ID of the host. See <literal>ConditionHost=</literal> in
 132           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 133           for details.</para>
 134         </listitem>
 135       </varlistentry>
 136       <varlistentry>
 137         <term><varname>Virtualization=</varname></term>
 138         <listitem>
 139           <para>Checks whether the system is executed in
 140           a virtualized environment and optionally test
 141           whether it is a specific implementation. See
 142           <literal>ConditionVirtualization=</literal> in
 143           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 144           for details.</para>
 145         </listitem>
 146       </varlistentry>
 147       <varlistentry>
 148         <term><varname>KernelCommandLine=</varname></term>
 149         <listitem>
 150           <para>Checks whether a specific kernel command line option
 151           is set (or if prefixed with the exclamation mark unset). See
 152           <literal>ConditionKernelCommandLine=</literal> in
 153           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 154           for details.</para>
 155         </listitem>
 156       </varlistentry>
 157         <varlistentry>
 158           <term><varname>KernelVersion=</varname></term>
 159           <listitem>
 160             <para>Checks whether the kernel version (as reported by <command>uname -r</command>) matches a certain
 161             expression (or if prefixed with the exclamation mark does not match it). See
 162             <literal>ConditionKernelVersion=</literal> in
 163             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 164             details.
 165             </para>
 166           </listitem>
 167         </varlistentry>
 168       <varlistentry>
 169         <term><varname>Architecture=</varname></term>
 170         <listitem>
 171           <para>Checks whether the system is running on a specific
 172           architecture. See <literal>ConditionArchitecture=</literal>
 173           in
 174           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 175           for details.</para>
 176         </listitem>
 177       </varlistentry>
 178     </variablelist>
 179
 180   </refsect1>
 181
 182   <refsect1>
 183     <title>[Link] Section Options</title>
 184
 185     <para>The <literal>[Link]</literal> section accepts the following
 186     keys:</para>
 187
 188     <variablelist class='network-directives'>
 189       <varlistentry>
 190         <term><varname>Description=</varname></term>
 191         <listitem>
 192           <para>A description of the device.</para>
 193         </listitem>
 194       </varlistentry>
 195       <varlistentry>
 196         <term><varname>Alias=</varname></term>
 197         <listitem>
 198           <para>The <literal>ifalias</literal> is set to this
 199           value.</para>
 200         </listitem>
 201       </varlistentry>
 202       <varlistentry>
 203         <term><varname>MACAddressPolicy=</varname></term>
 204         <listitem>
 205           <para>The policy by which the MAC address should be set. The
 206           available policies are:
 207           </para>
 208
 209           <variablelist>
 210             <varlistentry>
 211               <term><literal>persistent</literal></term>
 212               <listitem>
 213                 <para>If the hardware has a persistent MAC address, as
 214                 most hardware should, and if it is used by the kernel,
 215                 nothing is done. Otherwise, a new MAC address is
 216                 generated which is guaranteed to be the same on every
 217                 boot for the given machine and the given device, but
 218                 which is otherwise random. This feature depends on ID_NET_NAME_*
 219                 properties to exist for the link. On hardware where these
 220                 properties are not set, the generation of a persistent MAC address
 221                 will fail.</para>
 222               </listitem>
 223             </varlistentry>
 224             <varlistentry>
 225               <term><literal>random</literal></term>
 226               <listitem>
 227                 <para>If the kernel is using a random MAC address,
 228                 nothing is done. Otherwise, a new address is randomly
 229                 generated each time the device appears, typically at
 230                 boot. Either way, the random address will have the
 231                 <literal>unicast</literal> and
 232                 <literal>locally administered</literal> bits set.</para>
 233               </listitem>
 234             </varlistentry>
 235             <varlistentry>
 236               <term><literal>none</literal></term>
 237               <listitem>
 238                 <para>Keeps the MAC address assigned by the kernel.</para>
 239               </listitem>
 240             </varlistentry>
 241           </variablelist>
 242         </listitem>
 243       </varlistentry>
 244       <varlistentry>
 245         <term><varname>MACAddress=</varname></term>
 246         <listitem>
 247           <para>The MAC address to use, if no
 248           <literal>MACAddressPolicy=</literal>
 249           is specified.</para>
 250         </listitem>
 251       </varlistentry>
 252       <varlistentry>
 253         <term><varname>NamePolicy=</varname></term>
 254         <listitem>
 255           <para>An ordered, space-separated list of policies by which
 256           the interface name should be set.
 257           <literal>NamePolicy</literal> may be disabled by specifying
 258           <literal>net.ifnames=0</literal> on the kernel command line.
 259           Each of the policies may fail, and the first successful one
 260           is used. The name is not set directly, but is exported to
 261           udev as the property <literal>ID_NET_NAME</literal>, which
 262           is, by default, used by a udev rule to set
 263           <literal>NAME</literal>. If the name has already been set by
 264           userspace, no renaming is performed. The available policies
 265           are:</para>
 266
 267           <variablelist>
 268             <varlistentry>
 269               <term><literal>kernel</literal></term>
 270               <listitem>
 271                 <para>If the kernel claims that the name it has set
 272                 for a device is predictable, then no renaming is
 273                 performed.</para>
 274               </listitem>
 275             </varlistentry>
 276             <varlistentry>
 277               <term><literal>database</literal></term>
 278               <listitem>
 279                 <para>The name is set based on entries in the udev's
 280                 Hardware Database with the key
 281                 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
 282                 </para>
 283               </listitem>
 284             </varlistentry>
 285             <varlistentry>
 286               <term><literal>onboard</literal></term>
 287               <listitem>
 288                 <para>The name is set based on information given by
 289                 the firmware for on-board devices, as exported by the
 290                 udev property <literal>ID_NET_NAME_ONBOARD</literal>.
 291                 </para>
 292               </listitem>
 293             </varlistentry>
 294             <varlistentry>
 295               <term><literal>slot</literal></term>
 296               <listitem>
 297                 <para>The name is set based on information given by
 298                 the firmware for hot-plug devices, as exported by the
 299                 udev property <literal>ID_NET_NAME_SLOT</literal>.
 300                 </para>
 301               </listitem>
 302             </varlistentry>
 303             <varlistentry>
 304               <term><literal>path</literal></term>
 305               <listitem>
 306                 <para>The name is set based on the device's physical
 307                 location, as exported by the udev property
 308                 <literal>ID_NET_NAME_PATH</literal>.</para>
 309               </listitem>
 310             </varlistentry>
 311             <varlistentry>
 312               <term><literal>mac</literal></term>
 313               <listitem>
 314                 <para>The name is set based on the device's persistent
 315                 MAC address, as exported by the udev property
 316                 <literal>ID_NET_NAME_MAC</literal>.</para>
 317               </listitem>
 318             </varlistentry>
 319           </variablelist>
 320         </listitem>
 321       </varlistentry>
 322       <varlistentry>
 323         <term><varname>Name=</varname></term>
 324         <listitem>
 325           <para>The interface name to use in case all the
 326           policies specified in
 327           <varname>NamePolicy=</varname> fail, or in case
 328           <varname>NamePolicy=</varname> is missing or
 329           disabled.</para>
 330
 331           <para>Note that specifying a name that the kernel might use for another
 332           interface (for example <literal>eth0</literal>) is dangerous because the
 333           name assignment done by udev will race with the assignment done by the
 334           kernel, and only one interface may use the name. Depending on the order of
 335           operations, either udev or the kernel will win, making the naming
 336           unpredictable. It is best to use some different prefix, for example
 337           <literal>internal0</literal>/<literal>external0</literal> or
 338           <literal>lan0</literal>/<literal>lan1</literal>/<literal>lan3</literal>.
 339           </para>
 340         </listitem>
 341       </varlistentry>
 342       <varlistentry>
 343         <term><varname>MTUBytes=</varname></term>
 344         <listitem>
 345           <para>The maximum transmission unit in bytes to set for the
 346           device. The usual suffixes K, M, G, are supported and are
 347           understood to the base of 1024.</para>
 348         </listitem>
 349       </varlistentry>
 350       <varlistentry>
 351         <term><varname>BitsPerSecond=</varname></term>
 352         <listitem>
 353           <para>The speed to set for the device, the value is rounded
 354           down to the nearest Mbps. The usual suffixes K, M, G, are
 355           supported and are understood to the base of 1000.</para>
 356         </listitem>
 357       </varlistentry>
 358       <varlistentry>
 359         <term><varname>Duplex=</varname></term>
 360         <listitem>
 361           <para>The duplex mode to set for the device. The accepted
 362           values are <literal>half</literal> and
 363           <literal>full</literal>.</para>
 364         </listitem>
 365       </varlistentry>
 366       <varlistentry>
 367         <term><varname>AutoNegotiation=</varname></term>
 368         <listitem>
 369           <para>Enables or disables automatic negotiation of transmission parameters.
 370           Autonegotiation is a procedure by which two connected ethernet devices choose
 371           common transmission parameters, such as speed, duplex mode, and flow control.
 372           Takes a boolean value. Unset by default, which means that the kernel default
 373           will be used.</para>
 374
 375           <para>Note that if autonegotiation is enabled, speed and duplex settings are
 376           read-only. If autonegotation is disabled, speed and duplex settings are writable
 377           if the driver supports multiple link modes.</para>
 378         </listitem>
 379       </varlistentry>
 380       <varlistentry>
 381         <term><varname>WakeOnLan=</varname></term>
 382         <listitem>
 383           <para>The Wake-on-LAN policy to set for the device. The
 384           supported values are:</para>
 385
 386           <variablelist>
 387             <varlistentry>
 388               <term><literal>phy</literal></term>
 389               <listitem>
 390                 <para>Wake on PHY activity.</para>
 391               </listitem>
 392             </varlistentry>
 393             <varlistentry>
 394               <term><literal>unicast</literal></term>
 395               <listitem>
 396                 <para>Wake on unicast messages.</para>
 397               </listitem>
 398             </varlistentry>
 399             <varlistentry>
 400               <term><literal>multicast</literal></term>
 401               <listitem>
 402                 <para>Wake on multicast messages.</para>
 403               </listitem>
 404             </varlistentry>
 405             <varlistentry>
 406               <term><literal>broadcast</literal></term>
 407               <listitem>
 408                 <para>Wake on broadcast messages.</para>
 409               </listitem>
 410             </varlistentry>
 411             <varlistentry>
 412               <term><literal>arp</literal></term>
 413               <listitem>
 414                 <para>Wake on ARP.</para>
 415               </listitem>
 416             </varlistentry>
 417             <varlistentry>
 418               <term><literal>magic</literal></term>
 419               <listitem>
 420                 <para>Wake on receipt of a magic packet.
 421                 </para>
 422               </listitem>
 423             </varlistentry>
 424             <varlistentry>
 425               <term><literal>secureon</literal></term>
 426               <listitem>
 427                 <para>Enable secureon(tm) password for MagicPacket(tm).
 428                 </para>
 429               </listitem>
 430             </varlistentry>
 431             <varlistentry>
 432               <term><literal>off</literal></term>
 433               <listitem>
 434                 <para>Never wake.</para>
 435               </listitem>
 436             </varlistentry>
 437           </variablelist>
 438
 439           <para>Defaults to <literal>off</literal>.</para>
 440         </listitem>
 441       </varlistentry>
 442       <varlistentry>
 443         <term><varname>Port=</varname></term>
 444         <listitem>
 445           <para>The port option is used to select the device port. The
 446           supported values are:</para>
 447
 448           <variablelist>
 449             <varlistentry>
 450               <term><literal>tp</literal></term>
 451               <listitem>
 452                 <para>An Ethernet interface using Twisted-Pair cable as the medium.</para>
 453               </listitem>
 454             </varlistentry>
 455             <varlistentry>
 456               <term><literal>aui</literal></term>
 457               <listitem>
 458                 <para>Attachment Unit Interface (AUI). Normally used with hubs.
 459                 </para>
 460               </listitem>
 461             </varlistentry>
 462             <varlistentry>
 463               <term><literal>bnc</literal></term>
 464               <listitem>
 465                 <para>An Ethernet interface using BNC connectors and co-axial cable.</para>
 466               </listitem>
 467             </varlistentry>
 468             <varlistentry>
 469               <term><literal>mii</literal></term>
 470               <listitem>
 471                 <para>An Ethernet interface using a Media Independent Interface (MII).</para>
 472               </listitem>
 473             </varlistentry>
 474             <varlistentry>
 475               <term><literal>fibre</literal></term>
 476               <listitem>
 477                 <para>An Ethernet interface using Optical Fibre as the medium.</para>
 478               </listitem>
 479             </varlistentry>
 480           </variablelist>
 481         </listitem>
 482       </varlistentry>
 483       <varlistentry>
 484         <term><varname>TCPSegmentationOffload=</varname></term>
 485         <listitem>
 486           <para>The TCP Segmentation Offload (TSO) when true enables
 487           TCP segmentation offload. Takes a boolean value.
 488           Defaults to "unset".</para>
 489         </listitem>
 490       </varlistentry>
 491        <varlistentry>
 492       <term><varname>TCP6SegmentationOffload=</varname></term>
 493         <listitem>
 494           <para>The TCP6 Segmentation Offload (tx-tcp6-segmentation) when true enables
 495           TCP6 segmentation offload. Takes a boolean value.
 496           Defaults to "unset".</para>
 497         </listitem>
 498       </varlistentry>
 499       <varlistentry>
 500         <term><varname>GenericSegmentationOffload=</varname></term>
 501         <listitem>
 502           <para>The Generic Segmentation Offload (GSO) when true enables
 503           generic segmentation offload. Takes a boolean value.
 504           Defaults to "unset".</para>
 505         </listitem>
 506       </varlistentry>
 507     <varlistentry>
 508         <term><varname>GenericReceiveOffload=</varname></term>
 509         <listitem>
 510           <para>The Generic Receive Offload (GRO) when true enables
 511           generic receive offload. Takes a boolean value.
 512           Defaults to "unset".</para>
 513         </listitem>
 514       </varlistentry>
 515       <varlistentry>
 516         <term><varname>LargeReceiveOffload=</varname></term>
 517         <listitem>
 518           <para>The Large Receive Offload (LRO) when true enables
 519           large receive offload. Takes a boolean value.
 520           Defaults to "unset".</para>
 521         </listitem>
 522       </varlistentry>
 523       <varlistentry>
 524         <term><varname>RxChannels=</varname></term>
 525         <listitem>
 526           <para>Sets the number of receive channels (a number between 1 and 4294967295) .</para>
 527         </listitem>
 528       </varlistentry>
 529       <varlistentry>
 530         <term><varname>TxChannels=</varname></term>
 531         <listitem>
 532           <para>Sets the number of transmit channels (a number between 1 and 4294967295).</para>
 533         </listitem>
 534       </varlistentry>
 535       <varlistentry>
 536         <term><varname>OtherChannels=</varname></term>
 537         <listitem>
 538           <para>Sets the number of other channels (a number between 1 and 4294967295).</para>
 539         </listitem>
 540       </varlistentry>
 541       <varlistentry>
 542         <term><varname>CombinedChannels=</varname></term>
 543         <listitem>
 544           <para>Sets the number of combined set channels (a number between 1 and 4294967295).</para>
 545         </listitem>
 546       </varlistentry>
 547     </variablelist>
 548   </refsect1>
 549
 550   <refsect1>
 551     <title>Examples</title>
 552
 553     <example>
 554       <title>/usr/lib/systemd/network/99-default.link</title>
 555
 556       <para>The link file <filename>99-default.link</filename> that is
 557       shipped with systemd defines the default naming policy for
 558       links.</para>
 559
 560       <programlisting>[Link]
 561 NamePolicy=kernel database onboard slot path
 562 MACAddressPolicy=persistent</programlisting>
 563     </example>
 564
 565     <example>
 566       <title>/etc/systemd/network/10-dmz.link</title>
 567
 568       <para>This example assigns the fixed name
 569       <literal>dmz0</literal> to the interface with the MAC address
 570       00:a0:de:63:7a:e6:</para>
 571
 572       <programlisting>[Match]
 573 MACAddress=00:a0:de:63:7a:e6
 574
 575 [Link]
 576 Name=dmz0</programlisting>
 577     </example>
 578
 579     <example>
 580       <title>/etc/systemd/network/10-internet.link</title>
 581
 582       <para>This example assigns the fixed name
 583       <literal>internet0</literal> to the interface with the device
 584       path <literal>pci-0000:00:1a.0-*</literal>:</para>
 585
 586       <programlisting>[Match]
 587 Path=pci-0000:00:1a.0-*
 588
 589 [Link]
 590 Name=internet0</programlisting>
 591     </example>
 592
 593     <example>
 594       <title>/etc/systemd/network/25-wireless.link</title>
 595
 596       <para>Here's an overly complex example that shows the use of a large number of [Match] and [Link] settings.</para>
 597
 598       <programlisting>[Match]
 599 MACAddress=12:34:56:78:9a:bc
 600 Driver=brcmsmac
 601 Path=pci-0000:02:00.0-*
 602 Type=wlan
 603 Virtualization=no
 604 Host=my-laptop
 605 Architecture=x86-64
 606
 607 [Link]
 608 Name=wireless0
 609 MTUBytes=1450
 610 BitsPerSecond=10M
 611 WakeOnLan=magic
 612 MACAddress=cb:a9:87:65:43:21</programlisting>
 613     </example>
 614   </refsect1>
 615
 616   <refsect1>
 617     <title>See Also</title>
 618     <para>
 619       <citerefentry>
 620         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 621       </citerefentry>,
 622       <citerefentry>
 623         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 624       </citerefentry>,
 625       <citerefentry>
 626         <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 627       </citerefentry>,
 628       <citerefentry>
 629         <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 630       </citerefentry>
 631     </para>
 632   </refsect1>
 633
 634 </refentry>