man/systemd.link.xml

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  23
  24 <refentry id="systemd.link">
  25   <refentryinfo>
  26     <title>systemd.link</title>
  27     <productname>systemd</productname>
  28
  29     <authorgroup>
  30       <author>
  31         <contrib>Developer</contrib>
  32         <firstname>Tom</firstname>
  33         <surname>Gundersen</surname>
  34       </author>
  35     </authorgroup>
  36   </refentryinfo>
  37
  38   <refmeta>
  39     <refentrytitle>systemd.link</refentrytitle>
  40     <manvolnum>5</manvolnum>
  41   </refmeta>
  42
  43   <refnamediv>
  44     <refname>systemd.link</refname>
  45     <refpurpose>Network device configuration</refpurpose>
  46   </refnamediv>
  47
  48   <refsynopsisdiv>
  49     <para><filename><replaceable>link</replaceable>.link</filename></para>
  50   </refsynopsisdiv>
  51
  52   <refsect1>
  53     <title>Description</title>
  54
  55     <para>Network link configuration is performed by the
  56     <command>net_setup_link</command> udev builtin.</para>
  57
  58     <para>The link files are read from the files located in the system
  59     network directory <filename>/usr/lib/systemd/network</filename>,
  60     the volatile runtime network directory
  61     <filename>/run/systemd/network</filename>, and the local
  62     administration network directory
  63     <filename>/etc/systemd/network</filename>. Link files must have
  64     the extension <filename>.link</filename>; other extensions are
  65     ignored. All link files are collectively sorted and processed in
  66     lexical order, regardless of the directories in which they live.
  67     However, files with identical filenames replace each other. Files
  68     in <filename>/etc</filename> have the highest priority, files in
  69     <filename>/run</filename> take precedence over files with the same
  70     name in <filename>/usr/lib</filename>. This can be used to
  71     override a system-supplied link file with a local file if needed;
  72     a symlink in <filename>/etc</filename> with the same name as a
  73     link file in <filename>/usr/lib</filename>, pointing to
  74     <filename>/dev/null</filename>, disables the link file
  75     entirely.</para>
  76
  77     <para>The link file contains a <literal>[Match]</literal> section,
  78     which determines if a given link file may be applied to a given
  79     device, as well as a <literal>[Link]</literal> section specifying
  80     how the device should be configured. The first (in lexical order)
  81     of the link files that matches a given device is applied. Note
  82     that a default file <filename>99-default.link</filename> is
  83     shipped by the system, any user-supplied
  84     <filename>.link</filename> should hence have a lexically earlier
  85     name to be considered at all.</para>
  86   </refsect1>
  87
  88   <refsect1>
  89     <title>[Match] Section Options</title>
  90
  91     <para>A link file is said to match a device if each of the entries
  92     in the <literal>[Match]</literal> section matches, or if the
  93     section is empty. The following keys are accepted:</para>
  94
  95     <variablelist class='network-directives'>
  96       <varlistentry>
  97         <term><varname>MACAddress=</varname></term>
  98         <listitem>
  99           <para>The hardware address.</para>
 100         </listitem>
 101       </varlistentry>
 102       <varlistentry>
 103         <term><varname>OriginalName=</varname></term>
 104         <listitem>
 105           <para>A whitespace-separated list of shell-style globs matching
 106           the device name, as exposed by the udev property
 107           "INTERFACE". This can not be used to match on names that have
 108           already been changed from userspace. Caution is advised when matching on
 109           kernel-assigned names, as they are known to be unstable
 110           between reboots.</para>
 111         </listitem>
 112       </varlistentry>
 113       <varlistentry>
 114         <term><varname>Path=</varname></term>
 115         <listitem>
 116           <para>A whitespace-separated list of shell-style globs matching
 117           the persistent path, as exposed by the udev property
 118           <literal>ID_PATH</literal>.</para>
 119         </listitem>
 120       </varlistentry>
 121       <varlistentry>
 122         <term><varname>Driver=</varname></term>
 123         <listitem>
 124           <para>A whitespace-separated list of shell-style globs matching
 125           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>A whitespace-separated list of shell-style globs matching
 136           the device type, as exposed by the udev
 137           property <literal>DEVTYPE</literal>.</para>
 138         </listitem>
 139       </varlistentry>
 140       <varlistentry>
 141         <term><varname>Host=</varname></term>
 142         <listitem>
 143           <para>Matches against the hostname or machine
 144           ID of the host. See <literal>ConditionHost=</literal> in
 145           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 146           for details.</para>
 147         </listitem>
 148       </varlistentry>
 149       <varlistentry>
 150         <term><varname>Virtualization=</varname></term>
 151         <listitem>
 152           <para>Checks whether the system is executed in
 153           a virtualized environment and optionally test
 154           whether it is a specific implementation. See
 155           <literal>ConditionVirtualization=</literal> in
 156           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 157           for details.</para>
 158         </listitem>
 159       </varlistentry>
 160       <varlistentry>
 161         <term><varname>KernelCommandLine=</varname></term>
 162         <listitem>
 163           <para>Checks whether a specific kernel command line option
 164           is set (or if prefixed with the exclamation mark unset). See
 165           <literal>ConditionKernelCommandLine=</literal> in
 166           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 167           for details.</para>
 168         </listitem>
 169       </varlistentry>
 170       <varlistentry>
 171         <term><varname>Architecture=</varname></term>
 172         <listitem>
 173           <para>Checks whether the system is running on a specific
 174           architecture. See <literal>ConditionArchitecture=</literal>
 175           in
 176           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 177           for details.</para>
 178         </listitem>
 179       </varlistentry>
 180     </variablelist>
 181
 182   </refsect1>
 183
 184   <refsect1>
 185     <title>[Link] Section Options</title>
 186
 187     <para>The <literal>[Link]</literal> section accepts the following
 188     keys:</para>
 189
 190     <variablelist class='network-directives'>
 191       <varlistentry>
 192         <term><varname>Description=</varname></term>
 193         <listitem>
 194           <para>A description of the device.</para>
 195         </listitem>
 196       </varlistentry>
 197       <varlistentry>
 198         <term><varname>Alias=</varname></term>
 199         <listitem>
 200           <para>The <literal>ifalias</literal> is set to this
 201           value.</para>
 202         </listitem>
 203       </varlistentry>
 204       <varlistentry>
 205         <term><varname>MACAddressPolicy=</varname></term>
 206         <listitem>
 207           <para>The policy by which the MAC address should be set. The
 208           available policies are:
 209           </para>
 210
 211           <variablelist>
 212             <varlistentry>
 213               <term><literal>persistent</literal></term>
 214               <listitem>
 215                 <para>If the hardware has a persistent MAC address, as
 216                 most hardware should, and if it is used by the kernel,
 217                 nothing is done. Otherwise, a new MAC address is
 218                 generated which is guaranteed to be the same on every
 219                 boot for the given machine and the given device, but
 220                 which is otherwise random. This feature depends on ID_NET_NAME_*
 221                 properties existing for the link, on hardware where these
 222                 properties are not set the generation of a persistent MAC address
 223                 will fail.</para>
 224               </listitem>
 225             </varlistentry>
 226             <varlistentry>
 227               <term><literal>random</literal></term>
 228               <listitem>
 229                 <para>If the kernel is using a random MAC address,
 230                 nothing is done. Otherwise, a new address is randomly
 231                 generated each time the device appears, typically at
 232                 boot.</para>
 233               </listitem>
 234             </varlistentry>
 235           </variablelist>
 236         </listitem>
 237       </varlistentry>
 238       <varlistentry>
 239         <term><varname>MACAddress=</varname></term>
 240         <listitem>
 241           <para>The MAC address to use, if no
 242           <literal>MACAddressPolicy=</literal>
 243           is specified.</para>
 244         </listitem>
 245       </varlistentry>
 246       <varlistentry>
 247         <term><varname>NamePolicy=</varname></term>
 248         <listitem>
 249           <para>An ordered, space-separated list of policies by which
 250           the interface name should be set.
 251           <literal>NamePolicy</literal> may be disabled by specifying
 252           <literal>net.ifnames=0</literal> on the kernel command line.
 253           Each of the policies may fail, and the first successful one
 254           is used. The name is not set directly, but is exported to
 255           udev as the property <literal>ID_NET_NAME</literal>, which
 256           is, by default, used by a udev rule to set
 257           <literal>NAME</literal>. If the name has already been set by
 258           userspace, no renaming is performed. The available policies
 259           are:</para>
 260
 261           <variablelist>
 262             <varlistentry>
 263               <term><literal>kernel</literal></term>
 264               <listitem>
 265                 <para>If the kernel claims that the name it has set
 266                 for a device is predictable, then no renaming is
 267                 performed.</para>
 268               </listitem>
 269             </varlistentry>
 270             <varlistentry>
 271               <term><literal>database</literal></term>
 272               <listitem>
 273                 <para>The name is set based on entries in the udev's
 274                 Hardware Database with the key
 275                 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
 276                 </para>
 277               </listitem>
 278             </varlistentry>
 279             <varlistentry>
 280               <term><literal>onboard</literal></term>
 281               <listitem>
 282                 <para>The name is set based on information given by
 283                 the firmware for on-board devices, as exported by the
 284                 udev property <literal>ID_NET_NAME_ONBOARD</literal>.
 285                 </para>
 286               </listitem>
 287             </varlistentry>
 288             <varlistentry>
 289               <term><literal>slot</literal></term>
 290               <listitem>
 291                 <para>The name is set based on information given by
 292                 the firmware for hot-plug devices, as exported by the
 293                 udev property <literal>ID_NET_NAME_SLOT</literal>.
 294                 </para>
 295               </listitem>
 296             </varlistentry>
 297             <varlistentry>
 298               <term><literal>path</literal></term>
 299               <listitem>
 300                 <para>The name is set based on the device's physical
 301                 location, as exported by the udev property
 302                 <literal>ID_NET_NAME_PATH</literal>.</para>
 303               </listitem>
 304             </varlistentry>
 305             <varlistentry>
 306               <term><literal>mac</literal></term>
 307               <listitem>
 308                 <para>The name is set based on the device's persistent
 309                 MAC address, as exported by the udev property
 310                 <literal>ID_NET_NAME_MAC</literal>.</para>
 311               </listitem>
 312             </varlistentry>
 313           </variablelist>
 314         </listitem>
 315       </varlistentry>
 316       <varlistentry>
 317         <term><varname>Name=</varname></term>
 318         <listitem>
 319           <para>The interface name to use in case all the
 320           policies specified in
 321           <varname>NamePolicy=</varname> fail, or in case
 322           <varname>NamePolicy=</varname> is missing or
 323           disabled.</para>
 324         </listitem>
 325       </varlistentry>
 326       <varlistentry>
 327         <term><varname>MTUBytes=</varname></term>
 328         <listitem>
 329           <para>The maximum transmission unit in bytes to set for the
 330           device. The usual suffixes K, M, G, are supported and are
 331           understood to the base of 1024.</para>
 332         </listitem>
 333       </varlistentry>
 334       <varlistentry>
 335         <term><varname>BitsPerSecond=</varname></term>
 336         <listitem>
 337           <para>The speed to set for the device, the value is rounded
 338           down to the nearest Mbps. The usual suffixes K, M, G, are
 339           supported and are understood to the base of 1000.</para>
 340         </listitem>
 341       </varlistentry>
 342       <varlistentry>
 343         <term><varname>Duplex=</varname></term>
 344         <listitem>
 345           <para>The duplex mode to set for the device. The accepted
 346           values are <literal>half</literal> and
 347           <literal>full</literal>.</para>
 348         </listitem>
 349       </varlistentry>
 350       <varlistentry>
 351         <term><varname>WakeOnLan=</varname></term>
 352         <listitem>
 353           <para>The Wake-on-LAN policy to set for the device. The
 354           supported values are:</para>
 355
 356           <variablelist>
 357             <varlistentry>
 358               <term><literal>phy</literal></term>
 359               <listitem>
 360                 <para>Wake on PHY activity.</para>
 361               </listitem>
 362             </varlistentry>
 363             <varlistentry>
 364               <term><literal>magic</literal></term>
 365               <listitem>
 366                 <para>Wake on receipt of a magic packet.
 367                 </para>
 368               </listitem>
 369             </varlistentry>
 370             <varlistentry>
 371               <term><literal>off</literal></term>
 372               <listitem>
 373                 <para>Never wake.</para>
 374               </listitem>
 375             </varlistentry>
 376           </variablelist>
 377         </listitem>
 378       </varlistentry>
 379     </variablelist>
 380   </refsect1>
 381
 382   <refsect1>
 383     <title>Example</title>
 384     <example>
 385       <title>/etc/systemd/network/wireless.link</title>
 386
 387       <programlisting>[Match]
 388 MACAddress=12:34:56:78:9a:bc
 389 Driver=brcmsmac
 390 Path=pci-0000:02:00.0-*
 391 Type=wlan
 392 Virtualization=no
 393 Host=my-laptop
 394 Architecture=x86-64
 395
 396 [Link]
 397 Name=wireless0
 398 MTUBytes=1450
 399 BitsPerSecond=10M
 400 WakeOnLan=magic
 401 MACAddress=cb:a9:87:65:43:21</programlisting>
 402     </example>
 403   </refsect1>
 404
 405   <refsect1>
 406     <title>See Also</title>
 407     <para>
 408       <citerefentry>
 409         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 410       </citerefentry>,
 411       <citerefentry>
 412         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 413       </citerefentry>,
 414       <citerefentry>
 415         <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 416       </citerefentry>,
 417       <citerefentry>
 418         <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 419       </citerefentry>
 420     </para>
 421   </refsect1>
 422
 423 </refentry>