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     As a special case, an empty file (file size 0) or symlink with the
  73     same name pointing to <filename>/dev/null</filename> disables the
  74     configuration file entirely (it is "masked").</para>
  75
  76     <para>The link file contains a <literal>[Match]</literal> section,
  77     which determines if a given link file may be applied to a given
  78     device, as well as a <literal>[Link]</literal> section specifying
  79     how the device should be configured. The first (in lexical order)
  80     of the link files that matches a given device is applied. Note
  81     that a default file <filename>99-default.link</filename> is
  82     shipped by the system, any user-supplied
  83     <filename>.link</filename> should hence have a lexically earlier
  84     name to be considered at all.</para>
  85   </refsect1>
  86
  87   <refsect1>
  88     <title>[Match] Section Options</title>
  89
  90     <para>A link file is said to match a device if each of the entries
  91     in the <literal>[Match]</literal> section matches, or if the
  92     section is empty. The following keys are accepted:</para>
  93
  94     <variablelist class='network-directives'>
  95       <varlistentry>
  96         <term><varname>MACAddress=</varname></term>
  97         <listitem>
  98           <para>The hardware address.</para>
  99         </listitem>
 100       </varlistentry>
 101       <varlistentry>
 102         <term><varname>OriginalName=</varname></term>
 103         <listitem>
 104           <para>A whitespace-separated list of shell-style globs matching
 105           the device name, as exposed by the udev property
 106           "INTERFACE". This can not be used to match on names that have
 107           already been changed from userspace. Caution is advised when matching on
 108           kernel-assigned names, as they are known to be unstable
 109           between reboots.</para>
 110         </listitem>
 111       </varlistentry>
 112       <varlistentry>
 113         <term><varname>Path=</varname></term>
 114         <listitem>
 115           <para>A whitespace-separated list of shell-style globs matching
 116           the persistent path, as exposed by the udev property
 117           <literal>ID_PATH</literal>.</para>
 118         </listitem>
 119       </varlistentry>
 120       <varlistentry>
 121         <term><varname>Driver=</varname></term>
 122         <listitem>
 123           <para>A whitespace-separated list of shell-style globs matching
 124           the driver currently bound to the device,
 125           as exposed by the udev property <literal>DRIVER</literal>
 126           of its parent device, or if that is not set, the
 127           driver as exposed by <literal>ethtool -i</literal>
 128           of the device itself.</para>
 129         </listitem>
 130       </varlistentry>
 131       <varlistentry>
 132         <term><varname>Type=</varname></term>
 133         <listitem>
 134           <para>A whitespace-separated list of shell-style globs matching
 135           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 to exist 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. Either way, the random address will have the
 232                 <literal>unicast</literal> and
 233                 <literal>locally administered</literal> bits set.</para>
 234               </listitem>
 235             </varlistentry>
 236             <varlistentry>
 237               <term><literal>none</literal></term>
 238               <listitem>
 239                 <para>Keeps the MAC address assigned by the kernel.</para>
 240               </listitem>
 241             </varlistentry>
 242           </variablelist>
 243         </listitem>
 244       </varlistentry>
 245       <varlistentry>
 246         <term><varname>MACAddress=</varname></term>
 247         <listitem>
 248           <para>The MAC address to use, if no
 249           <literal>MACAddressPolicy=</literal>
 250           is specified.</para>
 251         </listitem>
 252       </varlistentry>
 253       <varlistentry>
 254         <term><varname>NamePolicy=</varname></term>
 255         <listitem>
 256           <para>An ordered, space-separated list of policies by which
 257           the interface name should be set.
 258           <literal>NamePolicy</literal> may be disabled by specifying
 259           <literal>net.ifnames=0</literal> on the kernel command line.
 260           Each of the policies may fail, and the first successful one
 261           is used. The name is not set directly, but is exported to
 262           udev as the property <literal>ID_NET_NAME</literal>, which
 263           is, by default, used by a udev rule to set
 264           <literal>NAME</literal>. If the name has already been set by
 265           userspace, no renaming is performed. The available policies
 266           are:</para>
 267
 268           <variablelist>
 269             <varlistentry>
 270               <term><literal>kernel</literal></term>
 271               <listitem>
 272                 <para>If the kernel claims that the name it has set
 273                 for a device is predictable, then no renaming is
 274                 performed.</para>
 275               </listitem>
 276             </varlistentry>
 277             <varlistentry>
 278               <term><literal>database</literal></term>
 279               <listitem>
 280                 <para>The name is set based on entries in the udev's
 281                 Hardware Database with the key
 282                 <literal>ID_NET_NAME_FROM_DATABASE</literal>.
 283                 </para>
 284               </listitem>
 285             </varlistentry>
 286             <varlistentry>
 287               <term><literal>onboard</literal></term>
 288               <listitem>
 289                 <para>The name is set based on information given by
 290                 the firmware for on-board devices, as exported by the
 291                 udev property <literal>ID_NET_NAME_ONBOARD</literal>.
 292                 </para>
 293               </listitem>
 294             </varlistentry>
 295             <varlistentry>
 296               <term><literal>slot</literal></term>
 297               <listitem>
 298                 <para>The name is set based on information given by
 299                 the firmware for hot-plug devices, as exported by the
 300                 udev property <literal>ID_NET_NAME_SLOT</literal>.
 301                 </para>
 302               </listitem>
 303             </varlistentry>
 304             <varlistentry>
 305               <term><literal>path</literal></term>
 306               <listitem>
 307                 <para>The name is set based on the device's physical
 308                 location, as exported by the udev property
 309                 <literal>ID_NET_NAME_PATH</literal>.</para>
 310               </listitem>
 311             </varlistentry>
 312             <varlistentry>
 313               <term><literal>mac</literal></term>
 314               <listitem>
 315                 <para>The name is set based on the device's persistent
 316                 MAC address, as exported by the udev property
 317                 <literal>ID_NET_NAME_MAC</literal>.</para>
 318               </listitem>
 319             </varlistentry>
 320           </variablelist>
 321         </listitem>
 322       </varlistentry>
 323       <varlistentry>
 324         <term><varname>Name=</varname></term>
 325         <listitem>
 326           <para>The interface name to use in case all the
 327           policies specified in
 328           <varname>NamePolicy=</varname> fail, or in case
 329           <varname>NamePolicy=</varname> is missing or
 330           disabled.</para>
 331         </listitem>
 332       </varlistentry>
 333       <varlistentry>
 334         <term><varname>MTUBytes=</varname></term>
 335         <listitem>
 336           <para>The maximum transmission unit in bytes to set for the
 337           device. The usual suffixes K, M, G, are supported and are
 338           understood to the base of 1024.</para>
 339         </listitem>
 340       </varlistentry>
 341       <varlistentry>
 342         <term><varname>BitsPerSecond=</varname></term>
 343         <listitem>
 344           <para>The speed to set for the device, the value is rounded
 345           down to the nearest Mbps. The usual suffixes K, M, G, are
 346           supported and are understood to the base of 1000.</para>
 347         </listitem>
 348       </varlistentry>
 349       <varlistentry>
 350         <term><varname>Duplex=</varname></term>
 351         <listitem>
 352           <para>The duplex mode to set for the device. The accepted
 353           values are <literal>half</literal> and
 354           <literal>full</literal>.</para>
 355         </listitem>
 356       </varlistentry>
 357       <varlistentry>
 358         <term><varname>WakeOnLan=</varname></term>
 359         <listitem>
 360           <para>The Wake-on-LAN policy to set for the device. The
 361           supported values are:</para>
 362
 363           <variablelist>
 364             <varlistentry>
 365               <term><literal>phy</literal></term>
 366               <listitem>
 367                 <para>Wake on PHY activity.</para>
 368               </listitem>
 369             </varlistentry>
 370             <varlistentry>
 371               <term><literal>magic</literal></term>
 372               <listitem>
 373                 <para>Wake on receipt of a magic packet.
 374                 </para>
 375               </listitem>
 376             </varlistentry>
 377             <varlistentry>
 378               <term><literal>off</literal></term>
 379               <listitem>
 380                 <para>Never wake.</para>
 381               </listitem>
 382             </varlistentry>
 383           </variablelist>
 384         </listitem>
 385       </varlistentry>
 386     </variablelist>
 387   </refsect1>
 388
 389   <refsect1>
 390     <title>Example</title>
 391     <example>
 392       <title>/etc/systemd/network/25-wireless.link</title>
 393
 394       <programlisting>[Match]
 395 MACAddress=12:34:56:78:9a:bc
 396 Driver=brcmsmac
 397 Path=pci-0000:02:00.0-*
 398 Type=wlan
 399 Virtualization=no
 400 Host=my-laptop
 401 Architecture=x86-64
 402
 403 [Link]
 404 Name=wireless0
 405 MTUBytes=1450
 406 BitsPerSecond=10M
 407 WakeOnLan=magic
 408 MACAddress=cb:a9:87:65:43:21</programlisting>
 409     </example>
 410   </refsect1>
 411
 412   <refsect1>
 413     <title>See Also</title>
 414     <para>
 415       <citerefentry>
 416         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 417       </citerefentry>,
 418       <citerefentry>
 419         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
 420       </citerefentry>,
 421       <citerefentry>
 422         <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum>
 423       </citerefentry>,
 424       <citerefentry>
 425         <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum>
 426       </citerefentry>
 427     </para>
 428   </refsect1>
 429
 430 </refentry>