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| Copyright 2014 Tom Gundersen |
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| |
| <refentry id="systemd.link"> |
| <refentryinfo> |
| <title>systemd.link</title> |
| <productname>systemd</productname> |
| |
| <authorgroup> |
| <author> |
| <contrib>Developer</contrib> |
| <firstname>Tom</firstname> |
| <surname>Gundersen</surname> |
| </author> |
| </authorgroup> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>systemd.link</refentrytitle> |
| <manvolnum>5</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>systemd.link</refname> |
| <refpurpose>Network device configuration</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <para><filename><replaceable>link</replaceable>.link</filename></para> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para>Network link configuration is performed by the |
| <command>net_setup_link</command> udev builtin.</para> |
| |
| <para>The link files are read from the files located in the system |
| network directory <filename>/lib/systemd/network</filename>, |
| the volatile runtime network directory |
| <filename>/run/systemd/network</filename>, and the local |
| administration network directory |
| <filename>/etc/systemd/network</filename>. Link files must have |
| the extension <filename>.link</filename>; other extensions are |
| ignored. All link files are collectively sorted and processed in |
| lexical order, regardless of the directories in which they live. |
| However, files with identical filenames replace each other. Files |
| in <filename>/etc</filename> have the highest priority, files in |
| <filename>/run</filename> take precedence over files with the same |
| name in <filename>/lib</filename>. This can be used to |
| override a system-supplied link file with a local file if needed. |
| As a special case, an empty file (file size 0) or symlink with the |
| same name pointing to <filename>/dev/null</filename> disables the |
| configuration file entirely (it is "masked").</para> |
| |
| <para>The link file contains a <literal>[Match]</literal> section, |
| which determines if a given link file may be applied to a given |
| device, as well as a <literal>[Link]</literal> section specifying |
| how the device should be configured. The first (in lexical order) |
| of the link files that matches a given device is applied. Note |
| that a default file <filename>99-default.link</filename> is |
| shipped by the system, any user-supplied |
| <filename>.link</filename> should hence have a lexically earlier |
| name to be considered at all.</para> |
| |
| <para>See |
| <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for diagnosing problems with <filename>.link</filename> files.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>[Match] Section Options</title> |
| |
| <para>A link file is said to match a device if each of the entries |
| in the <literal>[Match]</literal> section matches, or if the |
| section is empty. The following keys are accepted:</para> |
| |
| <variablelist class='network-directives'> |
| <varlistentry> |
| <term><varname>MACAddress=</varname></term> |
| <listitem> |
| <para>The hardware address.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>OriginalName=</varname></term> |
| <listitem> |
| <para>A whitespace-separated list of shell-style globs matching |
| the device name, as exposed by the udev property |
| "INTERFACE". This cannot be used to match on names that have |
| already been changed from userspace. Caution is advised when matching on |
| kernel-assigned names, as they are known to be unstable |
| between reboots.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Path=</varname></term> |
| <listitem> |
| <para>A whitespace-separated list of shell-style globs matching |
| the persistent path, as exposed by the udev property |
| <literal>ID_PATH</literal>.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Driver=</varname></term> |
| <listitem> |
| <para>A whitespace-separated list of shell-style globs matching |
| the driver currently bound to the device, |
| as exposed by the udev property <literal>DRIVER</literal> |
| of its parent device, or if that is not set, the |
| driver as exposed by <literal>ethtool -i</literal> |
| of the device itself.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Type=</varname></term> |
| <listitem> |
| <para>A whitespace-separated list of shell-style globs matching |
| the device type, as exposed by the udev |
| property <literal>DEVTYPE</literal>.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Host=</varname></term> |
| <listitem> |
| <para>Matches against the hostname or machine |
| ID of the host. See <literal>ConditionHost=</literal> in |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for details.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Virtualization=</varname></term> |
| <listitem> |
| <para>Checks whether the system is executed in |
| a virtualized environment and optionally test |
| whether it is a specific implementation. See |
| <literal>ConditionVirtualization=</literal> in |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for details.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>KernelCommandLine=</varname></term> |
| <listitem> |
| <para>Checks whether a specific kernel command line option |
| is set (or if prefixed with the exclamation mark unset). See |
| <literal>ConditionKernelCommandLine=</literal> in |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for details.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Architecture=</varname></term> |
| <listitem> |
| <para>Checks whether the system is running on a specific |
| architecture. See <literal>ConditionArchitecture=</literal> |
| in |
| <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
| for details.</para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| |
| </refsect1> |
| |
| <refsect1> |
| <title>[Link] Section Options</title> |
| |
| <para>The <literal>[Link]</literal> section accepts the following |
| keys:</para> |
| |
| <variablelist class='network-directives'> |
| <varlistentry> |
| <term><varname>Description=</varname></term> |
| <listitem> |
| <para>A description of the device.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Alias=</varname></term> |
| <listitem> |
| <para>The <literal>ifalias</literal> is set to this |
| value.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>MACAddressPolicy=</varname></term> |
| <listitem> |
| <para>The policy by which the MAC address should be set. The |
| available policies are: |
| </para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><literal>persistent</literal></term> |
| <listitem> |
| <para>If the hardware has a persistent MAC address, as |
| most hardware should, and if it is used by the kernel, |
| nothing is done. Otherwise, a new MAC address is |
| generated which is guaranteed to be the same on every |
| boot for the given machine and the given device, but |
| which is otherwise random. This feature depends on ID_NET_NAME_* |
| properties to exist for the link. On hardware where these |
| properties are not set, the generation of a persistent MAC address |
| will fail.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>random</literal></term> |
| <listitem> |
| <para>If the kernel is using a random MAC address, |
| nothing is done. Otherwise, a new address is randomly |
| generated each time the device appears, typically at |
| boot. Either way, the random address will have the |
| <literal>unicast</literal> and |
| <literal>locally administered</literal> bits set.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>none</literal></term> |
| <listitem> |
| <para>Keeps the MAC address assigned by the kernel.</para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>MACAddress=</varname></term> |
| <listitem> |
| <para>The MAC address to use, if no |
| <literal>MACAddressPolicy=</literal> |
| is specified.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>NamePolicy=</varname></term> |
| <listitem> |
| <para>An ordered, space-separated list of policies by which |
| the interface name should be set. |
| <literal>NamePolicy</literal> may be disabled by specifying |
| <literal>net.ifnames=0</literal> on the kernel command line. |
| Each of the policies may fail, and the first successful one |
| is used. The name is not set directly, but is exported to |
| udev as the property <literal>ID_NET_NAME</literal>, which |
| is, by default, used by a udev rule to set |
| <literal>NAME</literal>. If the name has already been set by |
| userspace, no renaming is performed. The available policies |
| are:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><literal>kernel</literal></term> |
| <listitem> |
| <para>If the kernel claims that the name it has set |
| for a device is predictable, then no renaming is |
| performed.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>database</literal></term> |
| <listitem> |
| <para>The name is set based on entries in the udev's |
| Hardware Database with the key |
| <literal>ID_NET_NAME_FROM_DATABASE</literal>. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>onboard</literal></term> |
| <listitem> |
| <para>The name is set based on information given by |
| the firmware for on-board devices, as exported by the |
| udev property <literal>ID_NET_NAME_ONBOARD</literal>. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>slot</literal></term> |
| <listitem> |
| <para>The name is set based on information given by |
| the firmware for hot-plug devices, as exported by the |
| udev property <literal>ID_NET_NAME_SLOT</literal>. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>path</literal></term> |
| <listitem> |
| <para>The name is set based on the device's physical |
| location, as exported by the udev property |
| <literal>ID_NET_NAME_PATH</literal>.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>mac</literal></term> |
| <listitem> |
| <para>The name is set based on the device's persistent |
| MAC address, as exported by the udev property |
| <literal>ID_NET_NAME_MAC</literal>.</para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Name=</varname></term> |
| <listitem> |
| <para>The interface name to use in case all the |
| policies specified in |
| <varname>NamePolicy=</varname> fail, or in case |
| <varname>NamePolicy=</varname> is missing or |
| disabled.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>MTUBytes=</varname></term> |
| <listitem> |
| <para>The maximum transmission unit in bytes to set for the |
| device. The usual suffixes K, M, G, are supported and are |
| understood to the base of 1024.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>BitsPerSecond=</varname></term> |
| <listitem> |
| <para>The speed to set for the device, the value is rounded |
| down to the nearest Mbps. The usual suffixes K, M, G, are |
| supported and are understood to the base of 1000.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Duplex=</varname></term> |
| <listitem> |
| <para>The duplex mode to set for the device. The accepted |
| values are <literal>half</literal> and |
| <literal>full</literal>.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>AutoNegotiation=</varname></term> |
| <listitem> |
| <para>Enables or disables automatic negotiation of transmission parameters. |
| Autonegotiation is a procedure by which two connected ethernet devices choose |
| common transmission parameters, such as speed, duplex mode, and flow control. |
| Takes a boolean value. Unset by default, which means that the kernel default |
| will be used.</para> |
| |
| <para>Note that if autonegotiation is enabled, speed and duplex settings are |
| read-only. If autonegotation is disabled, speed and duplex settings are writable |
| if the driver supports multiple link modes.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>WakeOnLan=</varname></term> |
| <listitem> |
| <para>The Wake-on-LAN policy to set for the device. The |
| supported values are:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><literal>phy</literal></term> |
| <listitem> |
| <para>Wake on PHY activity.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>magic</literal></term> |
| <listitem> |
| <para>Wake on receipt of a magic packet. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>off</literal></term> |
| <listitem> |
| <para>Never wake.</para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>Port=</varname></term> |
| <listitem> |
| <para>The port option is used to select the device port. The |
| supported values are:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><literal>tp</literal></term> |
| <listitem> |
| <para>An Ethernet interface using Twisted-Pair cable as the medium.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>aui</literal></term> |
| <listitem> |
| <para>Attachment Unit Interface (AUI). Normally used with hubs. |
| </para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>bnc</literal></term> |
| <listitem> |
| <para>An Ethernet interface using BNC connectors and co-axial cable.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>mii</literal></term> |
| <listitem> |
| <para>An Ethernet interface using a Media Independent Interface (MII).</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><literal>fibre</literal></term> |
| <listitem> |
| <para>An Ethernet interface using Optical Fibre as the medium.</para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>TCPSegmentationOffload=</varname></term> |
| <listitem> |
| <para>The TCP Segmentation Offload (TSO) when true enables |
| TCP segmentation offload. Takes a boolean value. |
| Defaults to "unset".</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>GenericSegmentationOffload=</varname></term> |
| <listitem> |
| <para>The Generic Segmentation Offload (GSO) when true enables |
| generic segmentation offload. Takes a boolean value. |
| Defaults to "unset".</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>UDPSegmentationOffload=</varname></term> |
| <listitem> |
| <para>The UDP Segmentation Offload (USO) when true enables |
| UDP segmentation offload. Takes a boolean value. |
| Defaults to "unset".</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>GenericReceiveOffload=</varname></term> |
| <listitem> |
| <para>The Generic Receive Offload (GRO) when true enables |
| generic receive offload. Takes a boolean value. |
| Defaults to "unset".</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><varname>LargeReceiveOffload=</varname></term> |
| <listitem> |
| <para>The Large Receive Offload (LRO) when true enables |
| large receive offload. Takes a boolean value. |
| Defaults to "unset".</para> |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Examples</title> |
| |
| <example> |
| <title>/lib/systemd/network/99-default.link</title> |
| |
| <para>The link file <filename>99-default.link</filename> that is |
| shipped with systemd defines the default naming policy for |
| links.</para> |
| |
| <programlisting>[Link] |
| NamePolicy=kernel database onboard slot path |
| MACAddressPolicy=persistent</programlisting> |
| </example> |
| |
| <example> |
| <title>/etc/systemd/network/10-dmz.link</title> |
| |
| <para>This example assigns the fixed name |
| <literal>dmz0</literal> to the interface with the MAC address |
| 00:a0:de:63:7a:e6:</para> |
| |
| <programlisting>[Match] |
| MACAddress=00:a0:de:63:7a:e6 |
| |
| [Link] |
| Name=dmz0</programlisting> |
| </example> |
| |
| <example> |
| <title>/etc/systemd/network/10-internet.link</title> |
| |
| <para>This example assigns the fixed name |
| <literal>internet0</literal> to the interface with the device |
| path <literal>pci-0000:00:1a.0-*</literal>:</para> |
| |
| <programlisting>[Match] |
| Path=pci-0000:00:1a.0-* |
| |
| [Link] |
| Name=internet0</programlisting> |
| </example> |
| |
| <example> |
| <title>/etc/systemd/network/25-wireless.link</title> |
| |
| <para>Here's an overly complex example that shows the use of a large number of [Match] and [Link] settings.</para> |
| |
| <programlisting>[Match] |
| MACAddress=12:34:56:78:9a:bc |
| Driver=brcmsmac |
| Path=pci-0000:02:00.0-* |
| Type=wlan |
| Virtualization=no |
| Host=my-laptop |
| Architecture=x86-64 |
| |
| [Link] |
| Name=wireless0 |
| MTUBytes=1450 |
| BitsPerSecond=10M |
| WakeOnLan=magic |
| MACAddress=cb:a9:87:65:43:21</programlisting> |
| </example> |
| </refsect1> |
| |
| <refsect1> |
| <title>See Also</title> |
| <para> |
| <citerefentry> |
| <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum> |
| </citerefentry>, |
| <citerefentry> |
| <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum> |
| </citerefentry>, |
| <citerefentry> |
| <refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum> |
| </citerefentry>, |
| <citerefentry> |
| <refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum> |
| </citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |