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<refentry id="systemd.device">

<refentryinfo>

<title>systemd.device</title>

<productname>systemd</productname>

<authorgroup>

<author>

<contrib>Developer</contrib>

<firstname>Lennart</firstname>

<surname>Poettering</surname>

<email>lennart@poettering.net</email>

</author>

</authorgroup>

</refentryinfo>

<refmeta>

<refentrytitle>systemd.device</refentrytitle>

<manvolnum>5</manvolnum>

</refmeta>

<refnamediv>

<refname>systemd.device</refname>

<refpurpose>systemd device configuration files</refpurpose>

</refnamediv>

<refsynopsisdiv>

<para><filename>systemd.device</filename></para>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para>A unit configuration file whose name ends in

<filename>.device</filename> encodes information about

a device unit as exposed in the

sysfs/<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>

device tree.</para>

<para>This unit type has no specific options. See

<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for the common options of all unit configuration

files. The common configuration items are configured

in the generic <literal>[Unit]</literal> and

<literal>[Install]</literal> sections. A separate

<literal>[Device]</literal> section does not exist,

since no device-specific options may be

configured.</para>

<para>systemd will automatically create dynamic device

units for all kernel devices that are marked with the

"systemd" udev tag (by default all block and network

devices, and a few others). This may be used to define

dependencies between devices and other

units.</para>

<para>Device units are named after the

<filename>/sys</filename> and

<filename>/dev</filename> paths they control. Example:

the device <filename>/dev/sda5</filename> is exposed

in systemd as <filename>dev-sda5.device</filename>. For

details about the escaping logic used to convert a

file system path to a unit name see

<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

</refsect1>

<refsect1>

<title>The udev Database</title>

<para>The settings of device units may either be

configured via unit files, or directly from the udev

database (which is recommended). The following udev

properties are understood by systemd:</para>

<variablelist>

<varlistentry>

<term><varname>SYSTEMD_WANTS=</varname></term>

<listitem><para>Adds dependencies of

type <varname>Wants</varname> from

this unit to all listed units. This

may be used to activate arbitrary

units, when a specific device becomes

available. Note that this and the

other tags are not taken into account

unless the device is tagged with the

"<literal>systemd</literal>" string in

the udev database, because otherwise

the device is not exposed as systemd

unit.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>SYSTEMD_ALIAS=</varname></term>

<listitem><para>Adds an additional

alias name to the device unit. This

must be an absolute path that is

automatically transformed into a unit

name. (See above.)</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>ID_MODEL_FROM_DATABASE=</varname></term>

<term><varname>ID_MODEL=</varname></term>

<listitem><para>If set, this property is

used as description string for the

device unit.</para></listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>