man/systemd.link.xml

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   7   This file is part of systemd.
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   9   Copyright 2014 Tom Gundersen
  10
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  24
  25 <refentry id="systemd.link">
  26   <refentryinfo>
  27     <title>systemd.link</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>Developer</contrib>
  33         <firstname>Tom</firstname>
  34         <surname>Gundersen</surname>
  35       </author>
  36     </authorgroup>
  37   </refentryinfo>
  38
  39   <refmeta>
  40     <refentrytitle>systemd.link</refentrytitle>
  41     <manvolnum>5</manvolnum>
  42   </refmeta>
  43
  44   <refnamediv>
  45     <refname>systemd.link</refname>
  46     <refpurpose>Network device configuration</refpurpose>
  47   </refnamediv>
  48
  49   <refsynopsisdiv>
  50     <para><filename><replaceable>link</replaceable>.link</filename></para>
  51   </refsynopsisdiv>
  52
  53   <refsect1>
  54     <title>Description</title>
  55
  56     <para>Network link configuration is performed by the
  57     <command>net_setup_link</command> udev builtin.</para>
  58
  59     <para>The link files are read from the files located in the system
  60     network directory <filename>/usr/lib/systemd/network</filename>,
  61     the volatile runtime network directory
  62     <filename>/run/systemd/network</filename>, and the local
  63     administration network directory
  64     <filename>/etc/systemd/network</filename>. Link files must have
  65     the extension <filename>.link</filename>; other extensions are
  66     ignored. All link files are collectively sorted and processed in
  67     lexical order, regardless of the directories in which they live.
  68     However, files with identical filenames replace each other. Files
  69     in <filename>/etc</filename> have the highest priority, files in
  70     <filename>/run</filename> take precedence over files with the same
  71     name in <filename>/usr/lib</filename>. This can be used to
  72     override a system-supplied link file with a local file if needed;
  73     a symlink in <filename>/etc</filename> with the same name as a
  74     link file in <filename>/usr/lib</filename>, pointing to
  75     <filename>/dev/null</filename>, disables the link file
  76     entirely.</para>
  77
  78     <para>The link file contains a <literal>[Match]</literal> section,
  79     which determines if a given link file may be applied to a given
  80     device, as well as a <literal>[Link]</literal> section specifying
  81     how the device should be configured. The first (in lexical order)
  82     of the link files that matches a given device is applied. Note
  83     that a default file <filename>99-default.link</filename> is
  84     shipped by the system, any user-supplied
  85     <filename>.link</filename> should hence have a lexically earlier
  86     name to be considered at all.</para>
  87   </refsect1>
  88
  89   <refsect1>
  90     <title>[Match] Section Options</title>
  91
  92     <para>A link file is said to match a device if each of the entries
  93     in the <literal>[Match]</literal> section matches, or if the
  94     section is empty. The following keys are accepted:</para>
  95
  96     <variablelist class='network-directives'>
  97       <varlistentry>
  98         <term><varname>MACAddress=</varname></term>
  99         <listitem>
 100           <para>The hardware address.</para>
 101         </listitem>
 102       </varlistentry>
 103       <varlistentry>
 104         <term><varname>OriginalName=</varname></term>
 105         <listitem>
 106           <para>The device name, as exposed by the udev property
 107           "INTERFACE". May contain shell style globs. This can not be
 108           used to match on names that have already been changed from
 109           userspace. Caution is advised when matching on
 110           kernel-assigned names, as they are known to be unstable
 111           between reboots.</para>
 112         </listitem>
 113       </varlistentry>
 114       <varlistentry>
 115         <term><varname>Path=</varname></term>
 116         <listitem>
 117           <para>The persistent path, as exposed by the
 118           udev property <literal>ID_PATH</literal>. May
 119           contain shell style globs.</para>
 120         </listitem>
 121       </varlistentry>
 122       <varlistentry>
 123         <term><varname>Driver=</varname></term>
 124         <listitem>
 125           <para>The driver currently bound to the device,
 126           as exposed by the udev property <literal>DRIVER</literal>
 127           of its parent device, or if that is not set, the
 128           driver as exposed by <literal>ethtool -i</literal>
 129           of the device itself.</para>
 130         </listitem>
 131       </varlistentry>
 132       <varlistentry>
 133         <term><varname>Type=</varname></term>
 134         <listitem>
 135           <para>The device type, as exposed by the udev
 136           property <literal>DEVTYPE</literal>.</para>
 137         </listitem>
 138       </varlistentry>
 139       <varlistentry>
 140         <term><varname>Host=</varname></term>
 141         <listitem>
 142           <para>Matches against the hostname or machine
 143           ID of the host. See <literal>ConditionHost=</literal> in
 144           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 145           for details.</para>
 146         </listitem>
 147       </varlistentry>
 148       <varlistentry>
 149         <term><varname>Virtualization=</varname></term>
 150         <listitem>
 151           <para>Checks whether the system is executed in
 152           a virtualized environment and optionally test
 153           whether it is a specific implementation. See
 154           <literal>ConditionVirtualization=</literal> in
 155           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 156           for details.</para>
 157         </listitem>
 158       </varlistentry>
 159       <varlistentry>
 160         <term><varname>KernelCommandLine=</varname></term>
 161         <listitem>
 162           <para>Checks whether a specific kernel command line option
 163           is set (or if prefixed with the exclamation mark unset). See
 164           <literal>ConditionKernelCommandLine=</literal> in
 165           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 166           for details.</para>
 167         </listitem>
 168       </varlistentry>
 169       <varlistentry>
 170         <term><varname>Architecture=</varname></term>
 171         <listitem>
 172           <para>Checks whether the system is running on a specific
 173           architecture. See <literal>ConditionArchitecture=</literal>
 174           in
 175           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 176           for details.</para>
 177         </listitem>
 178       </varlistentry>
 179     </variablelist>
 180
 181   </refsect1>
 182
 183   <refsect1>
 184     <title>[Link] Section Options</title>
 185
 186     <para>The <literal>[Link]</literal> section accepts the following
 187     keys:</para>
 188
 189     <variablelist class='network-directives'>
 190       <varlistentry>
 191         <term><varname>Description=</varname></term>
 192         <listitem>
 193           <para>A description of the device.</para>
 194         </listitem>
 195       </varlistentry>
 196       <varlistentry>
 197         <term><varname>Alias=</varname></term>
 198         <listitem>
 199           <para>The <literal>ifalias</literal> is set to this
 200           value.</para>
 201         </listitem>
 202       </varlistentry>
 203       <varlistentry>
 204         <term><varname>MACAddressPolicy=</varname></term>
 205         <listitem>
 206           <para>The policy by which the MAC address should be set. The
 207           available policies are:
 208           </para>
 209
 210           <variablelist>
 211             <varlistentry>
 212               <term><literal>persistent</literal></term>
 213               <listitem>
 214                 <para>If the hardware has a persistent MAC address, as
 215                 most hardware should, and if it is used by the kernel,
 216                 nothing is done. Otherwise, a new MAC address is
 217                 generated which is guaranteed to be the same on every
 218                 boot for the given machine and the given device, but
 219                 which is otherwise random. This feature depends on ID_NET_NAME_*
 220                 properties existing for the link, on hardware where these
 221                 properties are not set the generation of a persistent MAC address
 222                 will fail.</para>
 223               </listitem>
 224             </varlistentry>
 225             <varlistentry>
 226               <term><literal>random</literal></term>
 227               <listitem>
 228                 <para>If the kernel is using a random MAC address,
 229                 nothing is done. Otherwise, a new address is randomly
 230                 generated each time the device appears, typically at
 231                 boot.</para>
 232               </listitem>
 233             </varlistentry>
 234           </variablelist>
 235         </listitem>
 236       </varlistentry>
 237       <varlistentry>
 238         <term><varname>MACAddress=</varname></term>
 239         <listitem>
 240           <para>The MAC address to use, if no
 241           <literal>MACAddressPolicy=</literal>
 242           is specified.</para>
 243         </listitem>
 244       </varlistentry>
 245       <varlistentry>
 246         <term><varname>NamePolicy=</varname></term>
 247         <listitem>
 248           <para>An ordered, space-separated list of policies by which
 249           the interface name should be set.
 250           <literal>NamePolicy</literal> may be disabled by specifying
 251           <literal>net.ifnames=0</literal> on the kernel command line.
 252           Each of the policies may fail, and the first successful one
 253           is used. The name is not set directly, but is exported to
 254           udev as the property <literal>ID_NET_NAME</literal>, which
 255           is, by default, used by a udev rule to set
 256           <literal>NAME</literal>. If the name has already been set by
 257           userspace, no renaming is performed. The available policies
 258           are:</para>
 259
 260           <variablelist>
 261             <varlistentry>
 262               <term><literal>kernel</literal></term>
 263               <listitem>
 264                 <para>If the kernel claims that the name it has set
 265                 for a device is predictable, then no renaming is
 266                 performed.</para>
 267               </listitem>
 268             </varlistentry>
 269             <varlistentry>
 270               <term><literal>database</literal></term>
 271               <listitem>
 272                 <para>The name is set based on entries in the udev's
 273                 Hardware Database with the key
 274                 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
 275                 </para>
 276               </listitem>
 277             </varlistentry>
 278             <varlistentry>
 279               <term><literal>onboard</literal></term>
 280               <listitem>
 281                 <para>The name is set based on information given by
 282                 the firmware for on-board devices, as exported by the
 283                 udev property <literal>ID_NET_NAME_ONBOARD</literal>.
 284                 </para>
 285               </listitem>
 286             </varlistentry>
 287             <varlistentry>
 288               <term><literal>slot</literal></term>
 289               <listitem>
 290                 <para>The name is set based on information given by
 291                 the firmware for hot-plug devices, as exported by the
 292                 udev property <literal>ID_NET_NAME_SLOT</literal>.
 293                 </para>
 294               </listitem>
 295             </varlistentry>
 296             <varlistentry>
 297               <term><literal>path</literal></term>
 298               <listitem>
 299                 <para>The name is set based on the device's physical
 300                 location, as exported by the udev property
 301                 <literal>ID_NET_NAME_PATH</literal>.</para>
 302               </listitem>
 303             </varlistentry>
 304             <varlistentry>
 305               <term><literal>mac</literal></term>
 306               <listitem>
 307                 <para>The name is set based on the device's persistent
 308                 MAC address, as exported by the udev property
 309                 <literal>ID_NET_NAME_MAC</literal>.</para>
 310               </listitem>
 311             </varlistentry>
 312           </variablelist>
 313         </listitem>
 314       </varlistentry>
 315       <varlistentry>
 316         <term><varname>Name=</varname></term>
 317         <listitem>
 318           <para>The interface name to use in case all the
 319           policies specified in
 320           <varname>NamePolicy=</varname> fail, or in case
 321           <varname>NamePolicy=</varname> is missing or
 322           disabled.</para>
 323         </listitem>
 324       </varlistentry>
 325       <varlistentry>
 326         <term><varname>MTUBytes=</varname></term>
 327         <listitem>
 328           <para>The maximum transmission unit in bytes to set for the
 329           device. The usual suffixes K, M, G, are supported and are
 330           understood to the base of 1024.</para>
 331         </listitem>
 332       </varlistentry>
 333       <varlistentry>
 334         <term><varname>BitsPerSecond=</varname></term>
 335         <listitem>
 336           <para>The speed to set for the device, the value is rounded
 337           down to the nearest Mbps. The usual suffixes K, M, G, are
 338           supported and are understood to the base of 1000.</para>
 339         </listitem>
 340       </varlistentry>
 341       <varlistentry>
 342         <term><varname>Duplex=</varname></term>
 343         <listitem>
 344           <para>The duplex mode to set for the device. The accepted
 345           values are <literal>half</literal> and
 346           <literal>full</literal>.</para>
 347         </listitem>
 348       </varlistentry>
 349       <varlistentry>
 350         <term><varname>WakeOnLan=</varname></term>
 351         <listitem>
 352           <para>The Wake-on-LAN policy to set for the device. The
 353           supported values are:</para>
 354
 355           <variablelist>
 356             <varlistentry>
 357               <term><literal>phy</literal></term>
 358               <listitem>
 359                 <para>Wake on PHY activity.</para>
 360               </listitem>
 361             </varlistentry>
 362             <varlistentry>
 363               <term><literal>magic</literal></term>
 364               <listitem>
 365                 <para>Wake on receipt of a magic packet.
 366                 </para>
 367               </listitem>
 368             </varlistentry>
 369             <varlistentry>
 370               <term><literal>off</literal></term>
 371               <listitem>
 372                 <para>Never wake.</para>
 373               </listitem>
 374             </varlistentry>
 375           </variablelist>
 376         </listitem>
 377       </varlistentry>
 378     </variablelist>
 379   </refsect1>
 380
 381   <refsect1>
 382     <title>Example</title>
 383     <example>
 384       <title>/etc/systemd/network/wireless.link</title>
 385
 386       <programlisting>[Match]
 387 MACAddress=12:34:56:78:9a:bc
 388 Driver=brcmsmac
 389 Path=pci-0000:02:00.0-*
 390 Type=wlan
 391 Virtualization=no
 392 Host=my-laptop
 393 Architecture=x86-64
 394
 395 [Link]
 396 Name=wireless0
 397 MTUBytes=1450
 398 BitsPerSecond=10M
 399 WakeOnLan=magic
 400 MACAddress=cb:a9:87:65:43:21</programlisting>
 401     </example>
 402   </refsect1>
 403
 404   <refsect1>
 405     <title>See Also</title>
 406     <para>
 407       <citerefentry>
 408         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 409       </citerefentry>,
 410       <citerefentry>
 411         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 412       </citerefentry>,
 413       <citerefentry>
 414         <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 415       </citerefentry>,
 416       <citerefentry>
 417         <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 418       </citerefentry>
 419     </para>
 420   </refsect1>
 421
 422 </refentry>