mirror of
https://github.com/systemd/systemd-stable.git
synced 2024-12-24 21:34:08 +03:00
d8e1613ed2
For some unit types we have hundreds of options, and the reader may easily miss that more options are described in other pages. We already mentioned this in the introduction and then at the top of the option list, but it can't hurt to repeat the information. Also, add an (almost empty) Options section for the unit types which don't have any custom options. It is nicer to have the same page structure in all cases, so people can jump between pages for different types more easily.
172 lines
8.1 KiB
XML
172 lines
8.1 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
|
|
|
<refentry id="systemd.device">
|
|
<refentryinfo>
|
|
<title>systemd.device</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>systemd.device</refentrytitle>
|
|
<manvolnum>5</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>systemd.device</refname>
|
|
<refpurpose>Device unit configuration</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<para><filename><replaceable>device</replaceable>.device</filename></para>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para>A unit configuration file whose name ends in <literal>.device</literal> encodes information about a
|
|
device unit as exposed in the
|
|
sysfs/<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry> device
|
|
tree. This may be used to define dependencies between devices and other units.</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
|
|
[Unit] and [Install]
|
|
sections. A separate [Device] section does not
|
|
exist, since no device-specific options may be configured.</para>
|
|
|
|
<para>systemd will dynamically create device units for all kernel devices that are marked with the
|
|
<literal>systemd</literal> udev tag (by default all block and network devices, and a few others). Note
|
|
that <emphasis>if <filename>systemd-udev.service</filename> is not running, no device units will be
|
|
available (for example in a typical container)</emphasis>.</para>
|
|
|
|
<para>Device units are named after the <filename>/sys/</filename>
|
|
and <filename>/dev/</filename> paths they control. Example: the
|
|
device <filename index="false">/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>
|
|
|
|
<para>To tag a udev device, use <literal>TAG+="systemd"</literal> in the udev rules file, see
|
|
<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details.
|
|
</para>
|
|
|
|
<para>Device units will be reloaded by systemd whenever the
|
|
corresponding device generates a <literal>changed</literal> event.
|
|
Other units can use <varname>ReloadPropagatedFrom=</varname> to react
|
|
to that event.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Automatic Dependencies</title>
|
|
|
|
<refsect2>
|
|
<title>Implicit Dependencies</title>
|
|
|
|
<para>Many unit types automatically acquire dependencies on device
|
|
units of devices they require. For example,
|
|
<filename>.socket</filename> unit acquire dependencies on the
|
|
device units of the network interface specified in
|
|
<varname>BindToDevice=</varname>. Similar, swap and mount units
|
|
acquire dependencies on the units encapsulating their backing
|
|
block devices.</para>
|
|
</refsect2>
|
|
|
|
<refsect2>
|
|
<title>Default Dependencies</title>
|
|
|
|
<para>There are no default dependencies for device units.</para>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>The udev Database</title>
|
|
|
|
<para>Unit settings of device units may either be configured via unit files, or directly from the udev
|
|
database. The following udev device properties are understood by the service manager:</para>
|
|
|
|
<variablelist class='udev-directives'>
|
|
<varlistentry>
|
|
<term><varname>SYSTEMD_WANTS=</varname></term>
|
|
<term><varname>SYSTEMD_USER_WANTS=</varname></term>
|
|
<listitem><para>Adds dependencies of type <varname>Wants=</varname> from the device unit to the specified
|
|
units. <varname>SYSTEMD_WANTS=</varname> is read by the system service manager,
|
|
<varname>SYSTEMD_USER_WANTS=</varname> by user service manager instances. These properties may be used to
|
|
activate arbitrary units when a specific device becomes available.</para>
|
|
|
|
<para>Note that this and the other udev device properties are not taken into account unless the device is
|
|
tagged with the <literal>systemd</literal> tag in the udev database, because otherwise the device is not
|
|
exposed as a systemd unit (see above).</para>
|
|
|
|
<para>Note that systemd will only act on <varname>Wants=</varname> dependencies when a device first becomes
|
|
active. It will not act on them if they are added to devices that are already active. Use
|
|
<varname>SYSTEMD_READY=</varname> (see below) to configure when a udev device shall be considered active, and
|
|
thus when to trigger the dependencies.</para>
|
|
|
|
<!-- Note that we don't document here that we actually apply unit_name_mangle() to all specified names, since
|
|
that's kinda ugly, and people should instead specify correctly escaped names -->
|
|
|
|
<para>The specified property value should be a space-separated list of valid unit names. If a unit template
|
|
name is specified (that is, a unit name containing an <literal>@</literal> character indicating a unit name to
|
|
use for multiple instantiation, but with an empty instance name following the <literal>@</literal>), it will be
|
|
automatically instantiated by the device's <literal>sysfs</literal> path (that is: the path is escaped and
|
|
inserted as instance name into the template unit name). This is useful in order to instantiate a specific
|
|
template unit once for each device that appears and matches specific properties.</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>SYSTEMD_READY=</varname></term>
|
|
<listitem><para>If set to 0, systemd will consider this device unplugged even if it shows up in the udev
|
|
tree. If this property is unset or set to 1, the device will be considered plugged if it is visible in the udev
|
|
tree.</para>
|
|
|
|
<para>This option is useful for devices that initially show up in an uninitialized state in the tree, and for
|
|
which a <literal>changed</literal> event is generated the moment they are fully set up. Note that
|
|
<varname>SYSTEMD_WANTS=</varname> (see above) is not acted on as long as <varname>SYSTEMD_READY=0</varname> is
|
|
set for a device.</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>Options</title>
|
|
|
|
<para>Device unit files may include [Unit] and [Install] sections, which are described in
|
|
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. No
|
|
options specific to this file type are supported.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|