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systemd-stable/man/systemd.device.xml
Lennart Poettering 5430f7f2bc relicense to LGPLv2.1 (with exceptions)
We finally got the OK from all contributors with non-trivial commits to
relicense systemd from GPL2+ to LGPL2.1+.

Some udev bits continue to be GPL2+ for now, but we are looking into
relicensing them too, to allow free copy/paste of all code within
systemd.

The bits that used to be MIT continue to be MIT.

The big benefit of the relicensing is that closed source code may now
link against libsystemd-login.so and friends.
2012-04-12 00:24:39 +02:00

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
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<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>
</refentry>