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
  11   systemd is free software; you can redistribute it and/or modify it
  12   under the terms of the GNU Lesser General Public License as published by
  13   the Free Software Foundation; either version 2.1 of the License, or
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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 <command>net_setup_link</command>
  57                 udev builtin.</para>
  58
  59                 <para>The link files are read from the files located in the
  60                 system network directory <filename>/usr/lib/systemd/network</filename>,
  61                 the volatile runtime network directory <filename>/run/systemd/network</filename>,
  62                 and the local administration network directory <filename>/etc/systemd/network</filename>.
  63                 Link files must have the extension <filename>.link</filename>; other extensions are ignored.
  64                 All link files are collectively sorted and processed in lexical order,
  65                 regardless of the directories in which they live. However, files with
  66                 identical filenames replace each other. Files in <filename>/etc</filename>
  67                 have the highest priority, files in <filename>/run</filename> take precedence
  68                 over files with the same name in <filename>/usr/lib</filename>. This can be
  69                 used to override a system-supplied link file with a local file if needed;
  70                 a symlink in <filename>/etc</filename> with the same name as a link file in
  71                 <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
  72                 disables the link file entirely.</para>
  73
  74                 <para>The link file contains a <literal>[Match]</literal> section, which
  75                 determines if a given link file may be applied to a given device; and a
  76                 <literal>[Link]</literal> section specifying how the device should be
  77                 configured. The first (in lexical order) of the link files that matches
  78                 a given device is applied.</para>
  79         </refsect1>
  80
  81         <refsect1>
  82                 <title>[Match] Section Options</title>
  83
  84                 <para>A link file is said to match a device if each of the entries in the
  85                 <literal>[Match]</literal> section matches, or if the section is empty.
  86                 The following keys are accepted:</para>
  87
  88                 <variablelist class='network-directives'>
  89                         <varlistentry>
  90                                 <term><varname>MACAddress=</varname></term>
  91                                 <listitem>
  92                                         <para>The hardware address.</para>
  93                                 </listitem>
  94                         </varlistentry>
  95                         <varlistentry>
  96                                 <term><varname>OriginalName=</varname></term>
  97                                 <listitem>
  98                                         <para>The device name, as exposed by the udev
  99                                         property "INTERFACE". May contain shell style
 100                                         globs. This can not be used to match on names
 101                                         that have already been changed from userspace.
 102                                         Caution is advised when matching on
 103                                         kernel-assigned names, as they are known to
 104                                         be unstable between reboots.</para>
 105                                 </listitem>
 106                         </varlistentry>
 107                         <varlistentry>
 108                                 <term><varname>Path=</varname></term>
 109                                 <listitem>
 110                                         <para>The persistent path, as exposed by the
 111                                         udev property <literal>ID_PATH</literal>. May
 112                                         contain shell style globs.</para>
 113                                 </listitem>
 114                         </varlistentry>
 115                         <varlistentry>
 116                                 <term><varname>Driver=</varname></term>
 117                                 <listitem>
 118                                         <para>The driver currently bound to the device,
 119                                         as exposed by the udev property <literal>DRIVER</literal>
 120                                         of its parent device, or if that is not set, the
 121                                         driver as exposed by <literal>ethtool -i</literal>
 122                                         of the device itself.</para>
 123                                 </listitem>
 124                         </varlistentry>
 125                         <varlistentry>
 126                                 <term><varname>Type=</varname></term>
 127                                 <listitem>
 128                                         <para>The device type, as exposed by the udev
 129                                         property <literal>DEVTYPE</literal>.</para>
 130                                 </listitem>
 131                         </varlistentry>
 132                         <varlistentry>
 133                                 <term><varname>Host=</varname></term>
 134                                 <listitem>
 135                                         <para>Matches against the hostname or machine
 136                                         ID of the host. See <literal>ConditionHost=</literal> in
 137                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 138                                         for details.</para>
 139                                 </listitem>
 140                         </varlistentry>
 141                         <varlistentry>
 142                                 <term><varname>Virtualization=</varname></term>
 143                                 <listitem>
 144                                         <para>Checks whether the system is executed in
 145                                         a virtualized environment and optionally test
 146                                         whether it is a specific implementation. See
 147                                         <literal>ConditionVirtualization=</literal> in
 148                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 149                                         for details.</para>
 150                                 </listitem>
 151                         </varlistentry>
 152                         <varlistentry>
 153                                 <term><varname>KernelCommandLine=</varname></term>
 154                                 <listitem>
 155                                         <para>Checks whether a specific kernel command
 156                                         line option is set (or if prefixed with the
 157                                         exclamation mark unset). See
 158                                         <literal>ConditionKernelCommandLine=</literal> in
 159                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 160                                         for details.</para>
 161                                 </listitem>
 162                         </varlistentry>
 163                         <varlistentry>
 164                                 <term><varname>Architecture=</varname></term>
 165                                 <listitem>
 166                                         <para>Checks whether the system is running on a
 167                                         specific architecture. See
 168                                         <literal>ConditionArchitecture=</literal> in
 169                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 170                                         for details.</para>
 171                                 </listitem>
 172                         </varlistentry>
 173                 </variablelist>
 174
 175         </refsect1>
 176
 177         <refsect1>
 178                 <title>[Link] Section Options</title>
 179
 180                 <para>The <literal>[Link]</literal> section accepts the following
 181                 keys:</para>
 182
 183                 <variablelist class='network-directives'>
 184                         <varlistentry>
 185                                 <term><varname>Description=</varname></term>
 186                                 <listitem>
 187                                         <para>A description of the device.</para>
 188                                 </listitem>
 189                         </varlistentry>
 190                         <varlistentry>
 191                                 <term><varname>Alias=</varname></term>
 192                                 <listitem>
 193                                         <para>The <literal>ifalias</literal> is set to
 194                                         this value.</para>
 195                                 </listitem>
 196                         </varlistentry>
 197                         <varlistentry>
 198                                 <term><varname>MACAddressPolicy=</varname></term>
 199                                 <listitem>
 200                                         <para>The policy by which the MAC address
 201                                         should be set. The available policies are:
 202                                         </para>
 203
 204                                         <variablelist>
 205                                                 <varlistentry>
 206                                                         <term><literal>persistent</literal></term>
 207                                                         <listitem>
 208                                                                 <para>If the hardware has a persistent
 209                                                                 MAC address, as most hardware should,
 210                                                                 and if it is used by the kernel, nothing
 211                                                                 is done. Otherwise, a new MAC address
 212                                                                 is generated which is guaranteed to be
 213                                                                 the same on every boot for the given
 214                                                                 machine and the given device, but which
 215                                                                 is otherwise random.</para>
 216                                                         </listitem>
 217                                                 </varlistentry>
 218                                                 <varlistentry>
 219                                                         <term><literal>random</literal></term>
 220                                                         <listitem>
 221                                                                 <para>If the kernel is using a random MAC
 222                                                                 address, nothing is done. Otherwise, a new
 223                                                                 address is randomly generated each time the
 224                                                                 device appears, typically at boot.</para>
 225                                                         </listitem>
 226                                                 </varlistentry>
 227                                         </variablelist>
 228                                 </listitem>
 229                         </varlistentry>
 230                         <varlistentry>
 231                                 <term><varname>MACAddress=</varname></term>
 232                                 <listitem>
 233                                         <para>The MAC address to use, if no
 234                                         <literal>MACAddressPolicy=</literal>
 235                                         is specified.</para>
 236                                 </listitem>
 237                         </varlistentry>
 238                         <varlistentry>
 239                                 <term><varname>NamePolicy=</varname></term>
 240                                 <listitem>
 241                                         <para>An ordered, space-separated list of
 242                                         policies by which the interface name should
 243                                         be set. <literal>NamePolicy</literal> may be
 244                                         disabled by specifying
 245                                         <literal>net.ifnames=0</literal> on the kernel
 246                                         command line. Each of the policies may fail, and
 247                                         the first successful one is used. The name is
 248                                         not set directly, but is exported to udev as
 249                                         the property <literal>ID_NET_NAME</literal>,
 250                                         which is, by default, used by a udev rule to set
 251                                         <literal>NAME</literal>. If the name has already
 252                                         been set by userspace, no renaming is performed.
 253                                         The available policies are:</para>
 254
 255                                         <variablelist>
 256                                                 <varlistentry>
 257                                                         <term><literal>kernel</literal></term>
 258                                                         <listitem>
 259                                                                 <para>If the kernel claims that the name it
 260                                                                 has set for a device is predictable, then
 261                                                                 no renaming is performed.
 262                                                                 </para>
 263                                                         </listitem>
 264                                                 </varlistentry>
 265                                                 <varlistentry>
 266                                                         <term><literal>database</literal></term>
 267                                                         <listitem>
 268                                                                 <para>The name is set based on entries in
 269                                                                 the udev's Hardware Database with the key
 270                                                                 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
 271                                                                 </para>
 272                                                         </listitem>
 273                                                 </varlistentry>
 274                                                 <varlistentry>
 275                                                         <term><literal>onboard</literal></term>
 276                                                         <listitem>
 277                                                                 <para>The name is set based on information given by
 278                                                                 the firmware for on-board devices, as exported by
 279                                                                 the udev property <literal>ID_NET_NAME_ONBOARD</literal>.
 280                                                                 </para>
 281                                                         </listitem>
 282                                                 </varlistentry>
 283                                                 <varlistentry>
 284                                                         <term><literal>slot</literal></term>
 285                                                         <listitem>
 286                                                                 <para>The name is set based on information given by
 287                                                                 the firmware for hot-plug devices, as exported by
 288                                                                 the udev property <literal>ID_NET_NAME_SLOT</literal>.
 289                                                                 </para>
 290                                                         </listitem>
 291                                                 </varlistentry>
 292                                                 <varlistentry>
 293                                                         <term><literal>path</literal></term>
 294                                                         <listitem>
 295                                                                 <para>The name is set based on the device's physical
 296                                                                 location, as exported by the udev property
 297                                                                 <literal>ID_NET_NAME_PATH</literal>.</para>
 298                                                         </listitem>
 299                                                 </varlistentry>
 300                                                 <varlistentry>
 301                                                         <term><literal>mac</literal></term>
 302                                                         <listitem>
 303                                                                 <para>The name is set based on the device's
 304                                                                 persistent MAC address, as exported by the udev
 305                                                                 property <literal>ID_NET_NAME_MAC</literal>.</para>
 306                                                         </listitem>
 307                                                 </varlistentry>
 308                                         </variablelist>
 309                                 </listitem>
 310                         </varlistentry>
 311                         <varlistentry>
 312                                 <term><varname>Name=</varname></term>
 313                                 <listitem>
 314                                         <para>The interface name to use in case all the
 315                                         policies specified in
 316                                         <varname>NamePolicy=</varname> fail, or in case
 317                                         <varname>NamePolicy=</varname> is missing or
 318                                         disabled.</para>
 319                                 </listitem>
 320                         </varlistentry>
 321                         <varlistentry>
 322                                 <term><varname>MTUBytes=</varname></term>
 323                                 <listitem>
 324                                         <para>The maximum transmission unit in bytes to
 325                                         set for the device. The usual suffixes K, M, G,
 326                                         are supported and are understood to the base of
 327                                         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
 334                                         value is rounded down to the nearest Mbps.
 335                                         The usual suffixes K, M, G, are supported and
 336                                         are understood to the base of 1000.</para>
 337                                 </listitem>
 338                         </varlistentry>
 339                         <varlistentry>
 340                                 <term><varname>Duplex=</varname></term>
 341                                 <listitem>
 342                                         <para>The duplex mode to set for the device.
 343                                         The accepted values are <literal>half</literal>
 344                                         and <literal>full</literal>.</para>
 345                                 </listitem>
 346                         </varlistentry>
 347                         <varlistentry>
 348                                 <term><varname>WakeOnLan=</varname></term>
 349                                 <listitem>
 350                                         <para>The Wake-on-LAN policy to set for the
 351                                         device. The supported values are:</para>
 352
 353                                         <variablelist>
 354                                                 <varlistentry>
 355                                                         <term><literal>phy</literal></term>
 356                                                         <listitem>
 357                                                                 <para>Wake on PHY activity.</para>
 358                                                         </listitem>
 359                                                 </varlistentry>
 360                                                 <varlistentry>
 361                                                         <term><literal>magic</literal></term>
 362                                                         <listitem>
 363                                                                 <para>Wake on receipt of a magic packet.
 364                                                                 </para>
 365                                                         </listitem>
 366                                                 </varlistentry>
 367                                                 <varlistentry>
 368                                                         <term><literal>off</literal></term>
 369                                                         <listitem>
 370                                                                 <para>Never wake.</para>
 371                                                         </listitem>
 372                                                 </varlistentry>
 373                                         </variablelist>
 374                                 </listitem>
 375                         </varlistentry>
 376                 </variablelist>
 377         </refsect1>
 378
 379         <refsect1>
 380                 <title>Example</title>
 381                 <example>
 382                         <title>/etc/systemd/network/wireless.link</title>
 383
 384                         <programlisting>[Match]
 385 MACAddress=12:34:56:78:9a:bc
 386 Driver=brcmsmac
 387 Path=pci-0000:02:00.0-*
 388 Type=wlan
 389 Virtualization=no
 390 Host=my-laptop
 391 Architecture=x86-64
 392
 393 [Link]
 394 Name=wireless0
 395 MTUBytes=1450
 396 BitsPerSecond=10M
 397 WakeOnLan=magic
 398 MACAddress=cb:a9:87:65:43:21</programlisting>
 399                 </example>
 400         </refsect1>
 401
 402         <refsect1>
 403                 <title>See Also</title>
 404                 <para>
 405                         <citerefentry>
 406                                 <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 407                         </citerefentry>,
 408                         <citerefentry>
 409                                 <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 410                         </citerefentry>,
 411                         <citerefentry>
 412                                 <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 413                         </citerefentry>,
 414                         <citerefentry>
 415                                 <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 416                         </citerefentry>
 417                 </para>
 418         </refsect1>
 419
 420 </refentry>