<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2010 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<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>
<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
+ [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
<para>Device units are named after the <filename>/sys</filename>
and <filename>/dev</filename> paths they control. Example: the
- device <filename noindex='true'>/dev/sda5</filename> is exposed in
+ 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>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>
- <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>
+ <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>The settings of device units may either be configured via
- unit files, or directly from the udev database (which is
- recommended). The following udev device properties are understood
- by systemd:</para>
+ <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 all listed
- units. The first form is used by the system systemd instance,
- the second by user systemd instances. Those settings may be
- used to activate arbitrary units when a specific device
- becomes available.</para>
-
- <para>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 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 influence on
- which udev event to trigger the dependencies.
- </para></listitem>
+ <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>
<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. This property has
- no influence on the behavior when a device disappears from the
- udev tree.</para>
-
- <para>This option is useful to support 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>
+ <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>
projects / thirdparty / systemd.git / blobdiff