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.</para>
 220               </listitem>
 221             </varlistentry>
 222             <varlistentry>
 223               <term><literal>random</literal></term>
 224               <listitem>
 225                 <para>If the kernel is using a random MAC address,
 226                 nothing is done. Otherwise, a new address is randomly
 227                 generated each time the device appears, typically at
 228                 boot.</para>
 229               </listitem>
 230             </varlistentry>
 231           </variablelist>
 232         </listitem>
 233       </varlistentry>
 234       <varlistentry>
 235         <term><varname>MACAddress=</varname></term>
 236         <listitem>
 237           <para>The MAC address to use, if no
 238           <literal>MACAddressPolicy=</literal>
 239           is specified.</para>
 240         </listitem>
 241       </varlistentry>
 242       <varlistentry>
 243         <term><varname>NamePolicy=</varname></term>
 244         <listitem>
 245           <para>An ordered, space-separated list of policies by which
 246           the interface name should be set.
 247           <literal>NamePolicy</literal> may be disabled by specifying
 248           <literal>net.ifnames=0</literal> on the kernel command line.
 249           Each of the policies may fail, and the first successful one
 250           is used. The name is not set directly, but is exported to
 251           udev as the property <literal>ID_NET_NAME</literal>, which
 252           is, by default, used by a udev rule to set
 253           <literal>NAME</literal>. If the name has already been set by
 254           userspace, no renaming is performed. The available policies
 255           are:</para>
 256
 257           <variablelist>
 258             <varlistentry>
 259               <term><literal>kernel</literal></term>
 260               <listitem>
 261                 <para>If the kernel claims that the name it has set
 262                 for a device is predictable, then no renaming is
 263                 performed.</para>
 264               </listitem>
 265             </varlistentry>
 266             <varlistentry>
 267               <term><literal>database</literal></term>
 268               <listitem>
 269                 <para>The name is set based on entries in the udev's
 270                 Hardware Database with the key
 271                 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
 272                 </para>
 273               </listitem>
 274             </varlistentry>
 275             <varlistentry>
 276               <term><literal>onboard</literal></term>
 277               <listitem>
 278                 <para>The name is set based on information given by
 279                 the firmware for on-board devices, as exported by the
 280                 udev property <literal>ID_NET_NAME_ONBOARD</literal>.
 281                 </para>
 282               </listitem>
 283             </varlistentry>
 284             <varlistentry>
 285               <term><literal>slot</literal></term>
 286               <listitem>
 287                 <para>The name is set based on information given by
 288                 the firmware for hot-plug devices, as exported by the
 289                 udev property <literal>ID_NET_NAME_SLOT</literal>.
 290                 </para>
 291               </listitem>
 292             </varlistentry>
 293             <varlistentry>
 294               <term><literal>path</literal></term>
 295               <listitem>
 296                 <para>The name is set based on the device's physical
 297                 location, as exported by the udev property
 298                 <literal>ID_NET_NAME_PATH</literal>.</para>
 299               </listitem>
 300             </varlistentry>
 301             <varlistentry>
 302               <term><literal>mac</literal></term>
 303               <listitem>
 304                 <para>The name is set based on the device's persistent
 305                 MAC address, as exported by the udev property
 306                 <literal>ID_NET_NAME_MAC</literal>.</para>
 307               </listitem>
 308             </varlistentry>
 309           </variablelist>
 310         </listitem>
 311       </varlistentry>
 312       <varlistentry>
 313         <term><varname>Name=</varname></term>
 314         <listitem>
 315           <para>The interface name to use in case all the
 316           policies specified in
 317           <varname>NamePolicy=</varname> fail, or in case
 318           <varname>NamePolicy=</varname> is missing or
 319           disabled.</para>
 320         </listitem>
 321       </varlistentry>
 322       <varlistentry>
 323         <term><varname>MTUBytes=</varname></term>
 324         <listitem>
 325           <para>The maximum transmission unit in bytes to set for the
 326           device. The usual suffixes K, M, G, are supported and are
 327           understood to the base of 1024.</para>
 328         </listitem>
 329       </varlistentry>
 330       <varlistentry>
 331         <term><varname>BitsPerSecond=</varname></term>
 332         <listitem>
 333           <para>The speed to set for the device, the value is rounded
 334           down to the nearest Mbps. The usual suffixes K, M, G, are
 335           supported and are understood to the base of 1000.</para>
 336         </listitem>
 337       </varlistentry>
 338       <varlistentry>
 339         <term><varname>Duplex=</varname></term>
 340         <listitem>
 341           <para>The duplex mode to set for the device. The accepted
 342           values are <literal>half</literal> and
 343           <literal>full</literal>.</para>
 344         </listitem>
 345       </varlistentry>
 346       <varlistentry>
 347         <term><varname>WakeOnLan=</varname></term>
 348         <listitem>
 349           <para>The Wake-on-LAN policy to set for the device. The
 350           supported values are:</para>
 351
 352           <variablelist>
 353             <varlistentry>
 354               <term><literal>phy</literal></term>
 355               <listitem>
 356                 <para>Wake on PHY activity.</para>
 357               </listitem>
 358             </varlistentry>
 359             <varlistentry>
 360               <term><literal>magic</literal></term>
 361               <listitem>
 362                 <para>Wake on receipt of a magic packet.
 363                 </para>
 364               </listitem>
 365             </varlistentry>
 366             <varlistentry>
 367               <term><literal>off</literal></term>
 368               <listitem>
 369                 <para>Never wake.</para>
 370               </listitem>
 371             </varlistentry>
 372           </variablelist>
 373         </listitem>
 374       </varlistentry>
 375     </variablelist>
 376   </refsect1>
 377
 378   <refsect1>
 379     <title>Example</title>
 380     <example>
 381       <title>/etc/systemd/network/wireless.link</title>
 382
 383       <programlisting>[Match]
 384 MACAddress=12:34:56:78:9a:bc
 385 Driver=brcmsmac
 386 Path=pci-0000:02:00.0-*
 387 Type=wlan
 388 Virtualization=no
 389 Host=my-laptop
 390 Architecture=x86-64
 391
 392 [Link]
 393 Name=wireless0
 394 MTUBytes=1450
 395 BitsPerSecond=10M
 396 WakeOnLan=magic
 397 MACAddress=cb:a9:87:65:43:21</programlisting>
 398     </example>
 399   </refsect1>
 400
 401   <refsect1>
 402     <title>See Also</title>
 403     <para>
 404       <citerefentry>
 405         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 406       </citerefentry>,
 407       <citerefentry>
 408         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 409       </citerefentry>,
 410       <citerefentry>
 411         <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 412       </citerefentry>,
 413       <citerefentry>
 414         <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 415       </citerefentry>
 416     </para>
 417   </refsect1>
 418
 419 </refentry>