man/systemd.device.html

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  18   </style><a href="index.html">Index </a>·
  19   <a href="systemd.directives.html">Directives </a>·
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  22   <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 217</span><hr><div class="refentry"><a name="systemd.device"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd.device — Device unit configuration</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename"><em class="replaceable"><code>device</code></em>.device</code></p></div><div class="refsect1"><a name="idm214169484112"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p>A unit configuration file whose name ends in
  23                 "<code class="literal">.device</code>" encodes information about
  24                 a device unit as exposed in the
  25                 sysfs/<a href="udev.html"><span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span></a>
  26                 device tree.</p><p>This unit type has no specific options. See
  27                 <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>
  28                 for the common options of all unit configuration
  29                 files. The common configuration items are configured
  30                 in the generic "<code class="literal">[Unit]</code>" and
  31                 "<code class="literal">[Install]</code>" sections. A separate
  32                 "<code class="literal">[Device]</code>" section does not exist,
  33                 since no device-specific options may be
  34                 configured.</p><p>systemd will dynamically create device units for
  35                 all kernel devices that are marked with the "systemd"
  36                 udev tag (by default all block and network devices,
  37                 and a few others). This may be used to define
  38                 dependencies between devices and other units. To tag a
  39                 udev device, use "<code class="literal">TAG+="systemd"</code>" in
  40                 the udev rules file, see
  41                 <a href="udev.html"><span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span></a>
  42                 for details.</p><p>Device units are named after the
  43                 <code class="filename">/sys</code> and
  44                 <code class="filename">/dev</code> paths they control. Example:
  45                 the device <code class="filename">/dev/sda5</code> is exposed
  46                 in systemd as <code class="filename">dev-sda5.device</code>. For
  47                 details about the escaping logic used to convert a
  48                 file system path to a unit name see
  49                 <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>.</p></div><div class="refsect1"><a name="idm214169471024"></a><h2 id="The udev Database">The udev Database<a class="headerlink" title="Permalink to this headline" href="#The%20udev%20Database">¶</a></h2><p>The settings of device units may either be
  50                 configured via unit files, or directly from the udev
  51                 database (which is recommended). The following udev device
  52                 properties are understood by systemd:</p><div class="variablelist"><dl class="variablelist"><dt id="SYSTEMD_WANTS="><span class="term"><code class="varname">SYSTEMD_WANTS=</code>, </span><span class="term"><code class="varname">SYSTEMD_USER_WANTS=</code></span><a class="headerlink" title="Permalink to this term" href="#SYSTEMD_WANTS=">¶</a></dt><dd><p>Adds dependencies of
  53                                 type <code class="varname">Wants</code> from the
  54                                 device unit to all listed units. The
  55                                 first form is used by the system
  56                                 systemd instance, the second by user
  57                                 systemd instances. Those settings may
  58                                 be used to activate arbitrary units
  59                                 when a specific device becomes
  60                                 available.</p><p>Note that this and the
  61                                 other tags are not taken into account
  62                                 unless the device is tagged with the
  63                                 "<code class="literal">systemd</code>" string in
  64                                 the udev database, because otherwise
  65                                 the device is not exposed as a systemd
  66                                 unit (see above).</p><p>Note that systemd will only act
  67                                 on <code class="varname">Wants</code>
  68                                 dependencies when a device first
  69                                 becomes active. It will not act on
  70                                 them if they are added to devices that
  71                                 are already active. Use
  72                                 <code class="varname">SYSTEMD_READY=</code> (see
  73                                 below) to influence on which udev
  74                                 event to trigger the dependencies.
  75                                 </p></dd><dt id="SYSTEMD_ALIAS="><span class="term"><code class="varname">SYSTEMD_ALIAS=</code></span><a class="headerlink" title="Permalink to this term" href="#SYSTEMD_ALIAS=">¶</a></dt><dd><p>Adds an additional
  76                                 alias name to the device unit. This
  77                                 must be an absolute path that is
  78                                 automatically transformed into a unit
  79                                 name. (See above.)</p></dd><dt id="SYSTEMD_READY="><span class="term"><code class="varname">SYSTEMD_READY=</code></span><a class="headerlink" title="Permalink to this term" href="#SYSTEMD_READY=">¶</a></dt><dd><p>If set to 0, systemd
  80                                 will consider this device unplugged
  81                                 even if it shows up in the udev
  82                                 tree. If this property is unset or set
  83                                 to 1, the device will be considered
  84                                 plugged if it is visible in the
  85                                 udev tree. This property has no
  86                                 influence on the behavior when a
  87                                 device disappears from the udev
  88                                 tree.</p><p>This option is useful to support
  89                                 devices that initially show up in an
  90                                 uninitialized state in the tree, and
  91                                 for which a "<code class="literal">changed</code>"
  92                                 event is generated the moment they are
  93                                 fully set up. Note that
  94                                 <code class="varname">SYSTEMD_WANTS=</code> (see
  95                                 above) is not acted on as long as
  96                                 <code class="varname">SYSTEMD_READY=0</code> is
  97                                 set for a device.</p></dd><dt id="ID_MODEL_FROM_DATABASE="><span class="term"><code class="varname">ID_MODEL_FROM_DATABASE=</code>, </span><span class="term"><code class="varname">ID_MODEL=</code></span><a class="headerlink" title="Permalink to this term" href="#ID_MODEL_FROM_DATABASE=">¶</a></dt><dd><p>If set, this property is
  98                                 used as description string for the
  99                                 device unit.</p></dd></dl></div></div><div class="refsect1"><a name="idm214173405536"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
 100                           <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
 101                           <a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>,
 102                           <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>,
 103                           <a href="udev.html"><span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span></a>,
 104                           <a href="systemd.directives.html"><span class="citerefentry"><span class="refentrytitle">systemd.directives</span>(7)</span></a>
 105                   </p></div></div></body></html>