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| 18 | </style><a href="index.html">Index </a>· | |
| 19 | <a href="systemd.directives.html">Directives </a>· | |
| 20 | <a href="../python-systemd/index.html">Python </a>· | |
| 21 | <a href="../libudev/index.html">libudev </a>· | |
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22 | <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</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="idm140133170137984"></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 a device unit | |
| 24 | 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 files. The common | |
| 29 | configuration items are configured in the generic | |
| 30 | "<code class="literal">[Unit]</code>" and "<code class="literal">[Install]</code>" | |
| 31 | sections. A separate "<code class="literal">[Device]</code>" section does not | |
| 32 | exist, since no device-specific options may be configured.</p><p>systemd will dynamically create device units for all kernel | |
| 33 | devices that are marked with the "systemd" udev tag (by default | |
| 34 | all block and network devices, and a few others). This may be used | |
| 35 | to define dependencies between devices and other units. To tag a | |
| 36 | udev device, use "<code class="literal">TAG+="systemd"</code>" in the udev | |
| 37 | rules file, see | |
| 38 | <a href="udev.html"><span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span></a> | |
| 39 | for details.</p><p>Device units are named after the <code class="filename">/sys</code> | |
| 40 | and <code class="filename">/dev</code> paths they control. Example: the | |
| 41 | device <code class="filename">/dev/sda5</code> is exposed in | |
| 42 | systemd as <code class="filename">dev-sda5.device</code>. For details about | |
| 43 | the escaping logic used to convert a file system path to a unit | |
| 44 | name see | |
| 45 | <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>.</p></div><div class="refsect1"><a name="idm140133166577520"></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 configured via | |
| 46 | unit files, or directly from the udev database (which is | |
| 47 | recommended). The following udev device properties are understood | |
| 48 | 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 type | |
| 49 | <code class="varname">Wants</code> from the device unit to all listed | |
| 50 | units. The first form is used by the system systemd instance, | |
| 51 | the second by user systemd instances. Those settings may be | |
| 52 | used to activate arbitrary units when a specific device | |
| 53 | becomes available.</p><p>Note that this and the other tags are not taken into | |
| 54 | account unless the device is tagged with the | |
| 55 | "<code class="literal">systemd</code>" string in the udev database, | |
| 56 | because otherwise the device is not exposed as a systemd unit | |
| 57 | (see above).</p><p>Note that systemd will only act on | |
| 58 | <code class="varname">Wants</code> dependencies when a device first | |
| 59 | becomes active. It will not act on them if they are added to | |
| 60 | devices that are already active. Use | |
| 61 | <code class="varname">SYSTEMD_READY=</code> (see below) to influence on | |
| 62 | which udev event to trigger the dependencies. | |
| 63 | </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 alias name to the device | |
| 64 | unit. This must be an absolute path that is automatically | |
| 65 | transformed into a unit 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 will consider this device | |
| 66 | unplugged even if it shows up in the udev tree. If this | |
| 67 | property is unset or set to 1, the device will be considered | |
| 68 | plugged if it is visible in the udev tree. This property has | |
| 69 | no influence on the behavior when a device disappears from the | |
| 70 | udev tree.</p><p>This option is useful to support devices that initially | |
| 71 | show up in an uninitialized state in the tree, and for which a | |
| 72 | "<code class="literal">changed</code>" event is generated the moment they | |
| 73 | are fully set up. Note that <code class="varname">SYSTEMD_WANTS=</code> | |
| 74 | (see above) is not acted on as long as | |
| 75 | <code class="varname">SYSTEMD_READY=0</code> is set for a | |
| 76 | 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 used as description | |
| 77 | string for the device unit.</p></dd></dl></div></div><div class="refsect1"><a name="idm140133170279296"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p> | |
| 78 | <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>, | |
| 79 | <a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>, | |
| 80 | <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>, | |
| 81 | <a href="udev.html"><span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span></a>, | |
| 82 | <a href="systemd.directives.html"><span class="citerefentry"><span class="refentrytitle">systemd.directives</span>(7)</span></a> | |
| 83 | </p></div></div></body></html> |