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-<!--
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-
- Copyright 2010 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2 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
- General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
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+<!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+ -->
<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>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 the moment it shows up in the
- udev tree. This property has no
- influence on the behaviour when a
- device disappears from the udev
- tree. This option is useful to support
- devices that initially show up in an
- uninitialized state in the tree, and for
- which a changed event is generated the
- moment they are fully set
- up.</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>
+ <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.</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 dynamically create 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. 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 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
+ 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>
+
+ <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>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>
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