man/systemd.device.xml

<?xml version='1.0'?> <!--*-nxml-*-->
<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
<!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 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 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>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 class='udev-directives'>
                        <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 behavior 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>,
                          <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                  </para>
        </refsect1>

</refentry>