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697 lines
29 KiB
XML
697 lines
29 KiB
XML
<?xml version='1.0'?>
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<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="udev">
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<refentryinfo>
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<title>udev</title>
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<productname>udev</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>udev</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>udev</refname>
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<refpurpose>Linux dynamic device management</refpurpose>
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</refnamediv>
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<refsect1><title>Description</title>
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<para>udev supplies the system software with device events, manages permissions
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of device nodes and may create additional symlinks in the <filename>/dev</filename>
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directory, or renames network interfaces. The kernel usually just assigns unpredictable
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device names based on the order of discovery. Meaningful symlinks or network device
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names provide a way to reliably identify devices based on their properties or
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current configuration.</para>
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<para>The udev daemon, <citerefentry><refentrytitle>udevd</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>, receives device uevents directly from
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the kernel whenever a device is added or removed from the system, or it changes its
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state. When udev receives a device event, it matches its configured set of rules
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against various device attributes to identify the device. Rules that match may
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provide additional device information to be stored in the udev database or
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to be used to create meaningful symlink names.</para>
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<para>All device information udev processes is stored in the udev database and
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sent out to possible event subscribers. Access to all stored data and the event
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sources are provided by the library libudev.</para>
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</refsect1>
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<refsect1><title>Configuration</title>
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<para>udev configuration files are placed in <filename>/etc/udev/</filename>
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and <filename>/lib/udev/</filename>. All empty lines or lines beginning with
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'#' will be ignored.</para>
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<refsect2><title>Configuration file</title>
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<para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
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It consists of a set of variables allowing the user to override default udev values.
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The following variables can be set:</para>
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<variablelist>
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<varlistentry>
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<term><option>udev_root</option></term>
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<listitem>
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<para>Specifies where to place the device nodes in the filesystem.
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The default value is <filename>/dev</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>udev_log</option></term>
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<listitem>
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<para>The logging priority. Valid values are the numerical syslog priorities
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or their textual representations: <option>err</option>, <option>info</option>
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and <option>debug</option>.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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<refsect2><title>Rules files</title>
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<para>The udev rules are read from the files located in the
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default rules directory <filename>/lib/udev/rules.d/</filename>,
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the custom rules directory <filename>/etc/udev/rules.d/</filename>
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and the temporary rules directory <filename>/run/udev/rules.d/</filename>.
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All rule files are sorted and processed in lexical order, regardless
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in which of these directories they live. Files in
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<filename>/etc/udev/rules.d/</filename> have precedence over files with
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the same name in <filename>/lib/udev/rules.d/</filename>. This can be
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used to ignore a default rules file if needed.</para>
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<para>Rule files must end in <filename>.rules</filename>, other extensions
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are ignored.</para>
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<para>Every line in the rules file contains at least one key value pair.
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There are two kind of keys, match and assignment keys.
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If all match keys are matching against its value, the rule gets applied and the
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assign keys get the specified value assigned.</para>
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<para>A matching rule may rename a network interface, add symlinks
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pointing to the device node, or run a specified program as part of
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the event handling.</para>
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<para>A rule consists of a list of one or more key value pairs separated by
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a comma. Each key has a distinct operation, depending on the used operator. Valid
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operators are:</para>
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<variablelist>
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<varlistentry>
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<term><option>==</option></term>
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<listitem>
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<para>Compare for equality.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>!=</option></term>
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<listitem>
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<para>Compare for inequality.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>=</option></term>
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<listitem>
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<para>Assign a value to a key. Keys that represent a list are reset
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and only this single value is assigned.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>+=</option></term>
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<listitem>
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<para>Add the value to a key that holds a list of entries.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>:=</option></term>
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<listitem>
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<para>Assign a value to a key finally; disallow any later changes,
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which may be used to prevent changes by any later rules.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>The following key names can be used to match against device properties.
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Some of the keys also match against properties of the parent devices in sysfs,
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not only the device that has generated the event. If multiple keys that match
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a parent device are specified in a single rule, all these keys must match at
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one and the same parent device.</para>
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<variablelist>
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<varlistentry>
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<term><option>ACTION</option></term>
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<listitem>
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<para>Match the name of the event action.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>DEVPATH</option></term>
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<listitem>
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<para>Match the devpath of the event device.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>KERNEL</option></term>
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<listitem>
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<para>Match the name of the event device.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>NAME</option></term>
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<listitem>
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<para>Match the name of the node or network interface. It can
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be used once the NAME key has been set in one of the preceding
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rules.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>SYMLINK</option></term>
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<listitem>
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<para>Match the name of a symlink targeting the node. It can
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be used once a SYMLINK key has been set in one of the preceding
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rules. There may be multiple symlinks; only one needs to match.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>SUBSYSTEM</option></term>
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<listitem>
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<para>Match the subsystem of the event device.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>DRIVER</option></term>
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<listitem>
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<para>Match the driver name of the event device. Only set for devices
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which are bound to a driver at the time the event is generated.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ATTR{<replaceable>filename</replaceable>}</option></term>
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<listitem>
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<para>Match sysfs attribute values of the event device. Trailing
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whitespace in the attribute values is ignored, if the specified match
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value does not contain trailing whitespace itself.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>KERNELS</option></term>
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<listitem>
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<para>Search the devpath upwards for a matching device name.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>SUBSYSTEMS</option></term>
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<listitem>
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<para>Search the devpath upwards for a matching device subsystem name.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>DRIVERS</option></term>
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<listitem>
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<para>Search the devpath upwards for a matching device driver name.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ATTRS{<replaceable>filename</replaceable>}</option></term>
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<listitem>
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<para>Search the devpath upwards for a device with matching sysfs attribute values.
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If multiple <option>ATTRS</option> matches are specified, all of them
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must match on the same device. Trailing whitespace in the attribute values is ignored,
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if the specified match value does not contain trailing whitespace itself.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ENV{<replaceable>key</replaceable>}</option></term>
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<listitem>
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<para>Match against a device property value.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>TAG</option></term>
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<listitem>
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<para>Match against a device tag.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>TEST{<replaceable>octal mode mask</replaceable>}</option></term>
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<listitem>
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<para>Test the existence of a file. An octal mode mask can be specified
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if needed.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>PROGRAM</option></term>
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<listitem>
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<para>Execute a program. The key is true, if the program returns
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successfully. The device properties are made available to the
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executed program in the environment. The program's output printed to
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stdout, is available in the RESULT key.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>RESULT</option></term>
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<listitem>
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<para>Match the returned string of the last PROGRAM call. This key can
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be used in the same or in any later rule after a PROGRAM call.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>Most of the fields support a shell style pattern matching. The following
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pattern characters are supported:</para>
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<variablelist>
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<varlistentry>
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<term><option>*</option></term>
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<listitem>
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<para>Matches zero, or any number of characters.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>?</option></term>
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<listitem>
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<para>Matches any single character.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>[]</option></term>
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<listitem>
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<para>Matches any single character specified within the brackets. For
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example, the pattern string 'tty[SR]' would match either 'ttyS' or 'ttyR'.
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Ranges are also supported within this match with the '-' character.
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For example, to match on the range of all digits, the pattern [0-9] would
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be used. If the first character following the '[' is a '!', any characters
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not enclosed are matched.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>The following keys can get values assigned:</para>
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<variablelist>
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<varlistentry>
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<term><option>NAME</option></term>
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<listitem>
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<para>The name, a network interface should be renamed to. Or as
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a temporary workaround, the name a device node should be named.
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Usually the kernel provides the defined node name, or even creates
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and removes the node before udev even receives any event. Changing
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the node name from the kernel's default creates inconsistencies
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and is not supported. If the kernel and NAME specify different names,
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an error will be logged. Udev is only expected to handle device node
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permissions and to create additional symlinks, not to change
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kernel-provided device node names. Instead of renaming a device node,
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SYMLINK should be used. Symlink names must never conflict with
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device node names, it will result in unpredictable behavior.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>SYMLINK</option></term>
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<listitem>
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<para>The name of a symlink targeting the node. Every matching rule will add
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this value to the list of symlinks to be created. Multiple symlinks may be
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specified by separating the names by the space character. In case multiple
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devices claim the same name, the link will always point to the device with
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the highest link_priority. If the current device goes away, the links will
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be re-evaluated and the device with the next highest link_priority will own
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the link. If no link_priority is specified, the order of the devices, and
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which one of them will own the link, is undefined. Claiming the same name for
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a symlink, which is or might be used for a device node, may result in
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unexpected behavior and is not supported.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>OWNER, GROUP, MODE</option></term>
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<listitem>
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<para>The permissions for the device node. Every specified value overwrites
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the compiled-in default value.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ATTR{<replaceable>key</replaceable>}</option></term>
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<listitem>
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<para>The value that should be written to a sysfs attribute of the
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event device.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ENV{<replaceable>key</replaceable>}</option></term>
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<listitem>
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<para>Set a device property value. Property names with a leading '.'
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are not stored in the database or exported to external tool or events.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>TAG</option></term>
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<listitem>
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<para>Attach a tag to a device. This is used to filter events for users
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of libudev's monitor functionality, or to enumerate a group of tagged
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devices. The implementation can only work efficiently if only a few
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tags are attached to a device. It is only meant to be used in
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contexts with specific device filter requirements, and not as a
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general-purpose flag. Excessive use might result in inefficient event
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handling.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>RUN</option></term>
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<listitem>
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<para>Add a program to the list of programs to be executed for a specific
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device. This can only be used for very short running tasks. Running an
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event process for a long period of time may block all further events for
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this or a dependent device. Long running tasks need to be immediately
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detached from the event process itself.</para>
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<para>If no absolute path is given, the program is expected to live in
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<filename>/lib/udev</filename>, otherwise the absolute path must be
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specified. Program name and arguments are separated by spaces. Single quotes
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can be used to specify arguments with spaces.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>LABEL</option></term>
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<listitem>
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<para>Named label where a GOTO can jump to.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>GOTO</option></term>
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<listitem>
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<para>Jumps to the next LABEL with a matching name</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>IMPORT{<replaceable>type</replaceable>}</option></term>
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<listitem>
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<para>Import a set of variables as device properties,
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depending on <replaceable>type</replaceable>:</para>
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<variablelist>
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<varlistentry>
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<term><option>program</option></term>
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<listitem>
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<para>Execute an external program specified as the assigned value and
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import its output, which must be in environment key
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format. Path specification, command/argument separation,
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and quoting work like in <option>RUN</option>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>file</option></term>
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<listitem>
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<para>Import a text file specified as the assigned value, which must be in
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environment key format.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>db</option></term>
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<listitem>
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<para>Import a single property specified as the assigned value from the
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current device database. This works only if the database is already populated
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by an earlier event.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>cmdline</option></term>
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<listitem>
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<para>Import a single property from the kernel commandline. For simple flags
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the value of the property will be set to '1'.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>parent</option></term>
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<listitem>
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<para>Import the stored keys from the parent device by reading
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the database entry of the parent device. The value assigned to
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<option>IMPORT{parent}</option> is used as a filter of key names
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to import (with the same shell-style pattern matching used for
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comparisons).</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>If no option is given, udev will choose between <option>program</option>
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and <option>file</option> based on the executable bit of the file
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permissions.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>WAIT_FOR</option></term>
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<listitem>
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<para>Wait for a file to become available or until a 10
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seconds timeout expires. The path is relative to the sysfs device,
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i. e. if no path is specified this waits for an attribute to appear.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>OPTIONS</option></term>
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<listitem>
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<para>Rule and device options:</para>
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<variablelist>
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<varlistentry>
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<term><option>link_priority=<replaceable>value</replaceable></option></term>
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<listitem>
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<para>Specify the priority of the created symlinks. Devices with higher
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priorities overwrite existing symlinks of other devices. The default is 0.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>event_timeout=</option></term>
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<listitem>
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<para>Number of seconds an event will wait for operations to finish before it
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will terminate itself.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
|
|
<term><option>string_escape=<replaceable>none|replace</replaceable></option></term>
|
|
<listitem>
|
|
<para>Usually control and other possibly unsafe characters are replaced
|
|
in strings used for device naming. The mode of replacement can be specified
|
|
with this option.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><option>static_node=</option></term>
|
|
<listitem>
|
|
<para>Apply the permissions specified in this rule to a static device node with
|
|
the specified name. Static device nodes might be provided by kernel modules
|
|
or copied from <filename>/lib/udev/devices</filename>. These nodes might not have
|
|
a corresponding kernel device at the time udevd is started; they can trigger
|
|
automatic kernel module loading.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><option>watch</option></term>
|
|
<listitem>
|
|
<para>Watch the device node with inotify, when closed after being opened for
|
|
writing, a change uevent will be synthesised.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><option>nowatch</option></term>
|
|
<listitem>
|
|
<para>Disable the watching of a device node with inotify.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>The <option>NAME</option>, <option>SYMLINK</option>, <option>PROGRAM</option>,
|
|
<option>OWNER</option>, <option>GROUP</option>, <option>MODE</option> and <option>RUN</option>
|
|
fields support simple printf-like string substitutions. The <option>RUN</option>
|
|
format chars gets applied after all rules have been processed, right before the program
|
|
is executed. It allows the use of device properties set by earlier matching
|
|
rules. For all other fields, substitutions are applied while the individual rule is
|
|
being processed. The available substitutions are:</para>
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><option>$kernel</option>, <option>%k</option></term>
|
|
<listitem>
|
|
<para>The kernel name for this device.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$number</option>, <option>%n</option></term>
|
|
<listitem>
|
|
<para>The kernel number for this device. For example, 'sda3' has
|
|
kernel number of '3'</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$devpath</option>, <option>%p</option></term>
|
|
<listitem>
|
|
<para>The devpath of the device.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$id</option>, <option>%b</option></term>
|
|
<listitem>
|
|
<para>The name of the device matched while searching the devpath upwards for
|
|
<option>SUBSYSTEMS</option>, <option>KERNELS</option>, <option>DRIVERS</option> and <option>ATTRS</option>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$driver</option></term>
|
|
<listitem>
|
|
<para>The driver name of the device matched while searching the devpath upwards for
|
|
<option>SUBSYSTEMS</option>, <option>KERNELS</option>, <option>DRIVERS</option> and <option>ATTRS</option>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$attr{<replaceable>file</replaceable>}</option>, <option>%s{<replaceable>file</replaceable>}</option></term>
|
|
<listitem>
|
|
<para>The value of a sysfs attribute found at the device where
|
|
all keys of the rule have matched. If the matching device does not have
|
|
such an attribute, and a previous KERNELS, SUBSYSTEMS, DRIVERS, or
|
|
ATTRS test selected a parent device, use the attribute from that
|
|
parent device.
|
|
If the attribute is a symlink, the last element of the symlink target is
|
|
returned as the value.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$env{<replaceable>key</replaceable>}</option>, <option>%E{<replaceable>key</replaceable>}</option></term>
|
|
<listitem>
|
|
<para>A device property value.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$major</option>, <option>%M</option></term>
|
|
<listitem>
|
|
<para>The kernel major number for the device.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$minor</option>, <option>%m</option></term>
|
|
<listitem>
|
|
<para>The kernel minor number for the device.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$result</option>, <option>%c</option></term>
|
|
<listitem>
|
|
<para>The string returned by the external program requested with PROGRAM.
|
|
A single part of the string, separated by a space character may be selected
|
|
by specifying the part number as an attribute: <option>%c{N}</option>.
|
|
If the number is followed by the '+' char this part plus all remaining parts
|
|
of the result string are substituted: <option>%c{N+}</option></para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$parent</option>, <option>%P</option></term>
|
|
<listitem>
|
|
<para>The node name of the parent device.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$name</option></term>
|
|
<listitem>
|
|
<para>The current name of the device node. If not changed by a rule, it is the
|
|
name of the kernel device.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$links</option></term>
|
|
<listitem>
|
|
<para>The current list of symlinks, separated by a space character. The value is
|
|
only set if an earlier rule assigned a value, or during a remove events.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$root</option>, <option>%r</option></term>
|
|
<listitem>
|
|
<para>The udev_root value.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$sys</option>, <option>%S</option></term>
|
|
<listitem>
|
|
<para>The sysfs mount point.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$tempnode</option>, <option>%N</option></term>
|
|
<listitem>
|
|
<para>The name of a created temporary device node to provide access to
|
|
the device from a external program before the real node is created.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>%%</option></term>
|
|
<listitem>
|
|
<para>The '%' character itself.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><option>$$</option></term>
|
|
<listitem>
|
|
<para>The '$' character itself.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<refsect1><title>Author</title>
|
|
<para>Written by Greg Kroah-Hartman <email>greg@kroah.com</email> and
|
|
Kay Sievers <email>kay.sievers@vrfy.org</email>. With much help from
|
|
Dan Stekloff and many others.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para><citerefentry>
|
|
<refentrytitle>udevd</refentrytitle><manvolnum>8</manvolnum>
|
|
</citerefentry>,
|
|
<citerefentry>
|
|
<refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
|
|
</citerefentry></para>
|
|
</refsect1>
|
|
</refentry>
|