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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>systemd-udevd.service</title><meta name="generator" content="DocBook XSL Stylesheets V1.77.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><a href="index.html">Index </a>·
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 202</span><hr><div class="refentry"><a name="systemd-udevd.service"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd-udevd.service, systemd-udevd-control.socket, systemd-udevd-kernel.socket, systemd-udevd — Device event managing daemon</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename">systemd-udevd.service</code></p><p><code class="filename">systemd-udevd-control.socket</code></p><p><code class="filename">systemd-udevd-kernel.socket</code></p><div class="cmdsynopsis"><p><code class="command">/usr/lib/systemd/systemd-udevd</code> [<code class="option">--daemon</code>] [<code class="option">--debug</code>] [<code class="option">--children-max=</code>] [<code class="option">--exec-delay=</code>] [<code class="option">--resolve-names=early|late|never</code>] [<code class="option">--version</code>] [<code class="option">--help</code>]</p></div></div><div class="refsect1"><a name="idp3919520"></a><h2>Description</h2><p><span class="command"><strong>systemd-udevd</strong></span> listens to kernel uevents.
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For every event, systemd-udevd executes matching instructions
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specified in udev rules. See <a href="udev.html"><span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span></a>.</p><p>The behavior of the running daemon can be changed with
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<span class="command"><strong>udevadm control</strong></span>.</p></div><div class="refsect1"><a name="idp3923456"></a><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--daemon</code></span></dt><dd><p>Detach and run in the background.</p></dd><dt><span class="term"><code class="option">--debug</code></span></dt><dd><p>Print debug messages to stderr.</p></dd><dt><span class="term"><code class="option">--children-max=</code></span></dt><dd><p>Limit the number of events executed in parallel.</p></dd><dt><span class="term"><code class="option">--exec-delay=</code></span></dt><dd><p>Delay the execution of RUN instruction by the given
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number of seconds. This option might be useful when
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debugging system crashes during coldplug caused by loading
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non-working kernel modules.</p></dd><dt><span class="term"><code class="option">--resolve-names=</code></span></dt><dd><p>Specify when systemd-udevd should resolve names of users and groups.
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When set to <code class="option">early</code> (the default) names will be
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resolved when the rules are parsed. When set to
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<code class="option">late</code> names will be resolved for every event.
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When set to <code class="option">never</code> names will never be resolved
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and all devices will be owned by root.</p></dd><dt><span class="term"><code class="option">--version</code></span></dt><dd><p>Print version number.</p></dd><dt><span class="term"><code class="option">--help</code></span></dt><dd><p>Print help text.</p></dd></dl></div></div><div class="refsect1"><a name="idp37376"></a><h2>Environment</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="varname">$UDEV_LOG=</code></span></dt><dd><p>Set the logging priority.</p></dd></dl></div></div><div class="refsect1"><a name="idp47872"></a><h2>Kernel command line</h2><div class="variablelist"><p>Parameters starting with "rd." will be read when
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<span class="command"><strong>systemd-udevd</strong></span> is used in an initrd.</p><dl class="variablelist"><dt><span class="term"><code class="varname">udev.log-priority=</code>, </span><span class="term"><code class="varname">rd.udev.log-priority=</code></span></dt><dd><p>Set the logging priority.</p></dd><dt><span class="term"><code class="varname">udev.children-max=</code>, </span><span class="term"><code class="varname">rd.udev.children-max=</code></span></dt><dd><p>Limit the number of events executed in parallel.</p></dd><dt><span class="term"><code class="varname">udev.exec-delay=</code>, </span><span class="term"><code class="varname">rd.udev.exec-delay=</code></span></dt><dd><p>Delay the execution of RUN instruction by the given
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number of seconds. This option might be useful when
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debugging system crashes during coldplug caused by loading
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non-working kernel modules.</p></dd><dt><span class="term"><code class="varname">net.ifnames=</code></span></dt><dd><p>Network interfaces are renamed to give them predictable names
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when possible. It is enabled by default, specifying 0 disables it.</p></dd></dl></div></div><div class="refsect1"><a name="idp59232"></a><h2>Configuration file</h2><p>udev expects its main configuration file at <code class="filename">/etc/udev/udev.conf</code>.
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It consists of a set of variables allowing the user to override default udev values. All
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empty lines or lines beginning with '#' are ignored. The following variables can be
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set:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="varname">udev_log</code></span></dt><dd><p>The logging priority. Valid values are the numerical syslog priorities
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or their textual representations: <code class="option">err</code>, <code class="option">info</code>
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and <code class="option">debug</code>.</p></dd></dl></div></div><div class="refsect1"><a name="idp64784"></a><h2>See Also</h2><p><a href="udev.html"><span class="citerefentry"><span class="refentrytitle">udev</span>(7)</span></a>, <a href="udevadm.html"><span class="citerefentry"><span class="refentrytitle">udevadm</span>(8)</span></a></p></div></div></body></html>
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