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Diffstat (limited to 'src/grp-system/systemd/systemd.device.xml')
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diff --git a/src/grp-system/systemd/systemd.device.xml b/src/grp-system/systemd/systemd.device.xml new file mode 100644 index 0000000000..effed098dd --- /dev/null +++ b/src/grp-system/systemd/systemd.device.xml @@ -0,0 +1,182 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//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/>. +--> + +<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>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> + </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> + </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> + + <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> + </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. 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> + </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> |