systemd/man/systemd.device.xml
2010-07-07 01:38:56 +02:00

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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>