man/systemd.device.xml

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   7   This file is part of systemd.
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   9   Copyright 2010 Lennart Poettering
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  24
  25 <refentry id="systemd.device">
  26         <refentryinfo>
  27                 <title>systemd.device</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.device</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.device</refname>
  47                 <refpurpose>Device unit configuration</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename><replaceable>device</replaceable>.device</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>A unit configuration file whose name ends in
  58                 <filename>.device</filename> encodes information about
  59                 a device unit as exposed in the
  60                 sysfs/<citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  61                 device tree.</para>
  62
  63                 <para>This unit type has no specific options. See
  64                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  65                 for the common options of all unit configuration
  66                 files. The common configuration items are configured
  67                 in the generic <literal>[Unit]</literal> and
  68                 <literal>[Install]</literal> sections. A separate
  69                 <literal>[Device]</literal> section does not exist,
  70                 since no device-specific options may be
  71                 configured.</para>
  72
  73                 <para>systemd will automatically create dynamic device
  74                 units for all kernel devices that are marked with the
  75                 "systemd" udev tag (by default all block and network
  76                 devices, and a few others). This may be used to define
  77                 dependencies between devices and other
  78                 units.</para>
  79
  80                 <para>Device units are named after the
  81                 <filename>/sys</filename> and
  82                 <filename>/dev</filename> paths they control. Example:
  83                 the device <filename noindex='true'>/dev/sda5</filename> is exposed
  84                 in systemd as <filename>dev-sda5.device</filename>. For
  85                 details about the escaping logic used to convert a
  86                 file system path to a unit name see
  87                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
  88
  89         </refsect1>
  90
  91         <refsect1>
  92                 <title>The udev Database</title>
  93
  94                 <para>The settings of device units may either be
  95                 configured via unit files, or directly from the udev
  96                 database (which is recommended). The following udev
  97                 properties are understood by systemd:</para>
  98
  99                 <variablelist class='udev-directives'>
 100                         <varlistentry>
 101                                 <term><varname>SYSTEMD_WANTS=</varname></term>
 102                                 <listitem><para>Adds dependencies of
 103                                 type <varname>Wants</varname> from
 104                                 this unit to all listed units. This
 105                                 may be used to activate arbitrary
 106                                 units, when a specific device becomes
 107                                 available. Note that this and the
 108                                 other tags are not taken into account
 109                                 unless the device is tagged with the
 110                                 "<literal>systemd</literal>" string in
 111                                 the udev database, because otherwise
 112                                 the device is not exposed as systemd
 113                                 unit.</para></listitem>
 114                         </varlistentry>
 115
 116                         <varlistentry>
 117                                 <term><varname>SYSTEMD_ALIAS=</varname></term>
 118                                 <listitem><para>Adds an additional
 119                                 alias name to the device unit. This
 120                                 must be an absolute path that is
 121                                 automatically transformed into a unit
 122                                 name. (See above.)</para></listitem>
 123                         </varlistentry>
 124
 125                         <varlistentry>
 126                                 <term><varname>SYSTEMD_READY=</varname></term>
 127                                 <listitem><para>If set to 0 systemd
 128                                 will consider this device unplugged
 129                                 even if it shows up in the udev
 130                                 tree. If this property is unset or set
 131                                 to 1 the device will be considered
 132                                 plugged the moment it shows up in the
 133                                 udev tree. This property has no
 134                                 influence on the behavior when a
 135                                 device disappears from the udev
 136                                 tree. This option is useful to support
 137                                 devices that initially show up in an
 138                                 uninitialized state in the tree, and for
 139                                 which a changed event is generated the
 140                                 moment they are fully set
 141                                 up.</para></listitem>
 142                         </varlistentry>
 143
 144                         <varlistentry>
 145                                 <term><varname>ID_MODEL_FROM_DATABASE=</varname></term>
 146                                 <term><varname>ID_MODEL=</varname></term>
 147
 148                                 <listitem><para>If set, this property is
 149                                 used as description string for the
 150                                 device unit.</para></listitem>
 151                         </varlistentry>
 152
 153                 </variablelist>
 154
 155
 156         </refsect1>
 157
 158         <refsect1>
 159                   <title>See Also</title>
 160                   <para>
 161                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 162                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 163                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 164                           <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 165                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 166                   </para>
 167         </refsect1>
 168
 169 </refentry>