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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  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>Path=</varname></term>
  97                                 <listitem>
  98                                 <para>The persistent path, as exposed by the
  99                                 udev property <literal>ID_PATH</literal>. May
 100                                 contain shell style globs.</para>
 101                         </listitem>
 102                         </varlistentry>
 103                         <varlistentry>
 104                                 <term><varname>Driver=</varname></term>
 105                                 <listitem>
 106                                         <para>The driver currently bound to the device,
 107                                         as exposed by the udev property <literal>DRIVER</literal>
 108                                         of its parent device, or if that is not set, the
 109                                         driver as exposed by <literal>ethtool -i</literal>
 110                                         of the device itself.</para>
 111                                 </listitem>
 112                         </varlistentry>
 113                         <varlistentry>
 114                                 <term><varname>Type=</varname></term>
 115                                 <listitem>
 116                                         <para>The device type, as exposed by the udev
 117                                         property <literal>DEVTYPE</literal>.</para>
 118                                 </listitem>
 119                         </varlistentry>
 120                         <varlistentry>
 121                                 <term><varname>Host=</varname></term>
 122                                 <listitem>
 123                                         <para>Matches against the hostname or machine
 124                                         ID of the host. See <literal>ConditionHost=</literal> in
 125                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 126                                         for details.</para>
 127                                 </listitem>
 128                         </varlistentry>
 129                         <varlistentry>
 130                                 <term><varname>Virtualization=</varname></term>
 131                                 <listitem>
 132                                         <para>Checks whether the system is executed in
 133                                         a virtualized environment and optionally test
 134                                         whether it is a specific implementation. See
 135                                         <literal>ConditionVirtualization=</literal> in
 136                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 137                                         for details.</para>
 138                                 </listitem>
 139                         </varlistentry>
 140                         <varlistentry>
 141                                 <term><varname>KernelCommandLine=</varname></term>
 142                                 <listitem>
 143                                         <para>Checks whether a specific kernel command
 144                                         line option is set (or if prefixed with the
 145                                         exclamation mark unset). See
 146                                         <literal>ConditionKernelCommandLine=</literal> in
 147                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 148                                         for details.</para>
 149                                 </listitem>
 150                         </varlistentry>
 151                         <varlistentry>
 152                                 <term><varname>Architecture=</varname></term>
 153                                 <listitem>
 154                                         <para>Checks whether the system is running on a
 155                                         specific architecture. See
 156                                         <literal>ConditionArchitecture=</literal> in
 157                                         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 158                                         for details.</para>
 159                                 </listitem>
 160                         </varlistentry>
 161                 </variablelist>
 162
 163         </refsect1>
 164
 165         <refsect1>
 166                 <title>[Link] Section Options</title>
 167
 168                 <para>The <literal>[Link]</literal> section accepts the following
 169                 keys:</para>
 170
 171                 <variablelist class='network-directives'>
 172                         <varlistentry>
 173                                 <term><varname>Description=</varname></term>
 174                                 <listitem>
 175                                         <para>A description of the device.</para>
 176                                 </listitem>
 177                         </varlistentry>
 178                         <varlistentry>
 179                                 <term><varname>Alias=</varname></term>
 180                                 <listitem>
 181                                         <para>The <literal>ifalias</literal> is set to
 182                                         this value.</para>
 183                                 </listitem>
 184                         </varlistentry>
 185                         <varlistentry>
 186                                 <term><varname>MACAddressPolicy=</varname></term>
 187                                 <listitem>
 188                                         <para>The policy by which the MAC address
 189                                         should be set. The available policies are:
 190                                         </para>
 191
 192                                         <variablelist>
 193                                                 <varlistentry>
 194                                                         <term><literal>persistent</literal></term>
 195                                                         <listitem>
 196                                                                 <para>If the hardware has a persistent
 197                                                                 MAC address, as most hardware should,
 198                                                                 and if it is used by the kernel, nothing
 199                                                                 is done. Otherwise, a new MAC address
 200                                                                 is generated which is guaranteed to be
 201                                                                 the same on every boot for the given
 202                                                                 machine and the given device, but which
 203                                                                 is otherwise random.</para>
 204                                                         </listitem>
 205                                                 </varlistentry>
 206                                                 <varlistentry>
 207                                                         <term><literal>random</literal></term>
 208                                                         <listitem>
 209                                                                 <para>If the kernel is using a random MAC
 210                                                                 address, nothing is done. Otherwise, a new
 211                                                                 address is randomly generated each time the
 212                                                                 device appears, typically at boot.</para>
 213                                                         </listitem>
 214                                                 </varlistentry>
 215                                         </variablelist>
 216                                 </listitem>
 217                         </varlistentry>
 218                         <varlistentry>
 219                                 <term><varname>MACAddress=</varname></term>
 220                                 <listitem>
 221                                         <para>The MAC address to use, if no
 222                                         <literal>MACAddressPolicy=</literal>
 223                                         is specified.</para>
 224                                 </listitem>
 225                         </varlistentry>
 226                         <varlistentry>
 227                                 <term><varname>NamePolicy=</varname></term>
 228                                 <listitem>
 229                                         <para>An ordered, space-separated list of
 230                                         policies by which the interface name should
 231                                         be set. <literal>NamePolicy</literal> may be
 232                                         disabled by specifying
 233                                         <literal>net.ifnames=0</literal> on the kernel
 234                                         commandline. Each of the policies may fail, and
 235                                         the first successful one is used. The name is
 236                                         not set directly, but is exported to udev as
 237                                         the property <literal>ID_NET_NAME</literal>,
 238                                         which is, by default, used by a udev rule to set
 239                                         <literal>NAME</literal>. If the name has already
 240                                         been set by userspace, no renaming is performed.
 241                                         The available policies are:</para>
 242
 243                                         <variablelist>
 244                                                 <varlistentry>
 245                                                         <term><literal>kernel</literal></term>
 246                                                         <listitem>
 247                                                                 <para>If the kernel claims that the name it
 248                                                                 has set for a device is predictable, then
 249                                                                 no renaming is performed.
 250                                                                 </para>
 251                                                         </listitem>
 252                                                 </varlistentry>
 253                                                 <varlistentry>
 254                                                         <term><literal>database</literal></term>
 255                                                         <listitem>
 256                                                                 <para>The name is set based on entries in
 257                                                                 the udev's Hardware Database with the key
 258                                                                 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
 259                                                                 </para>
 260                                                         </listitem>
 261                                                 </varlistentry>
 262                                                 <varlistentry>
 263                                                         <term><literal>onboard</literal></term>
 264                                                         <listitem>
 265                                                                 <para>The name is set based on information given by
 266                                                                 the firmware for on-board devices, as exported by
 267                                                                 the udev property <literal>ID_NET_NAME_ONBOARD</literal>.
 268                                                                 </para>
 269                                                         </listitem>
 270                                                 </varlistentry>
 271                                                 <varlistentry>
 272                                                         <term><literal>slot</literal></term>
 273                                                         <listitem>
 274                                                                 <para>The name is set based on information given by
 275                                                                 the firmware for hot-plug devices, as exported by
 276                                                                 the udev property <literal>ID_NET_NAME_SLOT</literal>.
 277                                                                 </para>
 278                                                         </listitem>
 279                                                 </varlistentry>
 280                                                 <varlistentry>
 281                                                         <term><literal>path</literal></term>
 282                                                         <listitem>
 283                                                                 <para>The name is set based on the device's physical
 284                                                                 location, as exported by the udev property
 285                                                                 <literal>ID_NET_NAME_PATH</literal>.</para>
 286                                                         </listitem>
 287                                                 </varlistentry>
 288                                                 <varlistentry>
 289                                                         <term><literal>mac</literal></term>
 290                                                         <listitem>
 291                                                                 <para>The name is set based on the device's
 292                                                                 persistent MAC address, as exported by the udev
 293                                                                 property <literal>ID_NET_NAME_MAC</literal>.</para>
 294                                                         </listitem>
 295                                                 </varlistentry>
 296                                         </variablelist>
 297                                 </listitem>
 298                         </varlistentry>
 299                         <varlistentry>
 300                                 <term><varname>Name=</varname></term>
 301                                 <listitem>
 302                                         <para>The interface name to use in case all the
 303                                         policies specified in
 304                                         <varname>NamePolicy=</varname> fail, or in case
 305                                         <varname>NamePolicy=</varname> is missing or
 306                                         disabled.</para>
 307                                 </listitem>
 308                         </varlistentry>
 309                         <varlistentry>
 310                                 <term><varname>MTUBytes=</varname></term>
 311                                 <listitem>
 312                                         <para>The maximum transmission unit in bytes to
 313                                         set for the device. The usual suffixes K, M, G,
 314                                         are supported and are understood to the base of
 315                                         1024.</para>
 316                                 </listitem>
 317                         </varlistentry>
 318                         <varlistentry>
 319                                 <term><varname>BitsPerSecond=</varname></term>
 320                                 <listitem>
 321                                         <para>The speed to set for the device, the
 322                                         value is rounded down to the nearest Mbps.
 323                                         The usual suffixes K, M, G, are supported and
 324                                         are understood to the base of 1000.</para>
 325                                 </listitem>
 326                         </varlistentry>
 327                         <varlistentry>
 328                                 <term><varname>Duplex=</varname></term>
 329                                 <listitem>
 330                                         <para>The duplex mode to set for the device.
 331                                         The accepted values are <literal>half</literal>
 332                                         and <literal>full</literal>.</para>
 333                                 </listitem>
 334                         </varlistentry>
 335                         <varlistentry>
 336                                 <term><varname>WakeOnLan=</varname></term>
 337                                 <listitem>
 338                                         <para>The Wake-on-LAN policy to set for the
 339                                         device. The supported values are:</para>
 340
 341                                         <variablelist>
 342                                                 <varlistentry>
 343                                                         <term><literal>phy</literal></term>
 344                                                         <listitem>
 345                                                                 <para>Wake on PHY activity.</para>
 346                                                         </listitem>
 347                                                 </varlistentry>
 348                                                 <varlistentry>
 349                                                         <term><literal>magic</literal></term>
 350                                                         <listitem>
 351                                                                 <para>Wake on receipt of a magic packet.
 352                                                                 </para>
 353                                                         </listitem>
 354                                                 </varlistentry>
 355                                                 <varlistentry>
 356                                                         <term><literal>off</literal></term>
 357                                                         <listitem>
 358                                                                 <para>Never wake.</para>
 359                                                         </listitem>
 360                                                 </varlistentry>
 361                                         </variablelist>
 362                                 </listitem>
 363                         </varlistentry>
 364                 </variablelist>
 365         </refsect1>
 366
 367         <refsect1>
 368                 <title>Example</title>
 369                 <example>
 370                         <title>/etc/systemd/network/wireless.link</title>
 371
 372                         <programlisting>[Match]
 373 MACAddress=12:34:56:78:9a:bc
 374 Driver=brcmsmac
 375 Path=pci-0000:02:00.0-*
 376 Type=wlan
 377 Virtualization=no
 378 Host=my-laptop
 379 Architecture=x86-64
 380
 381 [Link]
 382 Name=wireless0
 383 MTUBytes=1450
 384 BitsPerSecond=10M
 385 WakeOnLan=magic
 386 MACAddress=cb:a9:87:65:43:21</programlisting>
 387                 </example>
 388         </refsect1>
 389
 390         <refsect1>
 391                 <title>See Also</title>
 392                 <para>
 393                         <citerefentry>
 394                                 <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 395                         </citerefentry>,
 396                         <citerefentry>
 397                                 <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 398                         </citerefentry>
 399                 </para>
 400         </refsect1>
 401
 402 </refentry>