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-<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-<article>
- <section>
+<refentry id="udev">
+ <refentryinfo>
<title>udev</title>
- <refentry>
- <refentryinfo>
- <title>udev</title>
- <productname>udev</productname>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>udev</refentrytitle>
- <manvolnum>7</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>udev</refname>
- <refpurpose>dynamic device management</refpurpose>
- </refnamediv>
-
- <refsect1><title>DESCRIPTION</title>
- <para>udev provides a dynamic device directory containing only the files for
- actually present devices. It creates or removes device node files in the
- <filename>/dev</filename> directory, or it renames network interfaces.</para>
-
- <para>Usually udev runs as <citerefentry><refentrytitle>udevd</refentrytitle>
- <manvolnum>8</manvolnum></citerefentry> and receives uevents directly from the
- kernel if a device is added or removed from the system.</para>
-
- <para>If udev receives a device event, it matches its configured rules
- against the available device attributes provided in sysfs to identify the device.
- Rules that match may provide additional device information or specify a device
- node name and multiple symlink names and instruct udev to run additional programs
- as part of the device event handling.</para>
- </refsect1>
-
- <refsect1><title>CONFIGURATION</title>
- <para>udev configuration files are placed in <filename>/etc/udev/</filename>
- and <filename>/lib/udev/</filename>. All empty lines, or lines beginning with
- '#' will be ignored.</para>
-
- <refsect2><title>Configuration file</title>
- <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
- It consists of a set of variables allowing the user to override default udev values.
- The following variables can be set:</para>
- <variablelist>
- <varlistentry>
- <term><option>udev_root</option></term>
- <listitem>
- <para>Specifies where to place the device nodes in the filesystem.
- The default value is <filename>/dev</filename>.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>udev_log</option></term>
- <listitem>
- <para>The logging priority. Valid values are the numerical syslog priorities
- or their textual representations: <option>err</option>, <option>info</option>
- and <option>debug</option>.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect2>
-
- <refsect2><title>Rules files</title>
- <para>The udev rules are read from the files located in the
- default rules directory <filename>/lib/udev/rules.d/</filename>,
- the custom rules directory <filename>/etc/udev/rules.d/</filename>
- and the temporary rules directory <filename>/dev/.udev/rules.d/</filename>.
- All rule files are sorted and processed in lexical order, regardless
- in which of these directories they live.</para>
-
- <para>Rule files are required to have a unique name, duplicate file names
- are ignored. Files in <filename>/etc/udev/rules.d/</filename> have precedence
- over files with the same name in <filename>/lib/udev/rules.d/</filename>. This
- can be used to ignore a default rules file if needed.</para>
-
- <para>Every line in the rules file contains at least one key value pair.
- There are two kind of keys, match and assignment keys.
- If all match keys are matching against its value, the rule gets applied and the
- assign keys get the specified value assigned.</para>
-
- <para>A matching rule may specify the name of the device node, add a symlink
- pointing to the node, or run a specified program as part of the event handling.
- If no matching rule is found, the default device node name is used.</para>
-
- <para>A rule consists of a list of one or more key value pairs separated by
- a comma. Each key has a distinct operation, depending on the used operator. Valid
- operators are:</para>
- <variablelist>
- <varlistentry>
- <term><option>==</option></term>
- <listitem>
- <para>Compare for equality.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>!=</option></term>
- <listitem>
- <para>Compare for inequality.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>=</option></term>
- <listitem>
- <para>Assign a value to a key. Keys that represent a list, are reset
- and only this single value is assigned.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>+=</option></term>
- <listitem>
- <para>Add the value to a key that holds a list of entries.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>:=</option></term>
- <listitem>
- <para>Assign a value to a key finally; disallow any later changes,
- which may be used to prevent changes by any later rules.</para>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <para>The following key names can be used to match against device properties.
- Some of the keys also match against properties of the parent devices in sysfs,
- not only the device that has generated the event. If multiple keys that match
- a parent device are specified in a single rule, all these keys must match at
- one and the same parent device.</para>
- <variablelist>
- <varlistentry>
- <term><option>ACTION</option></term>
- <listitem>
- <para>Match the name of the event action.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>DEVPATH</option></term>
- <listitem>
- <para>Match the devpath of the event device.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>KERNEL</option></term>
- <listitem>
- <para>Match the name of the event device.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>NAME</option></term>
- <listitem>
- <para>Match the name of the node or network interface. It can
- be used once the NAME key has been set in one of the preceding
- rules.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>SYMLINK</option></term>
- <listitem>
- <para>Match the name of a symlink targeting the node. It can
- be used once a SYMLINK key has been set in one of the preceding
- rules. There may be multiple symlinks; only one needs to match.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>SUBSYSTEM</option></term>
- <listitem>
- <para>Match the subsystem of the event device.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>DRIVER</option></term>
- <listitem>
- <para>Match the driver name of the event device. Only set for devices
- which are bound to a driver at the time the event is generated.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>ATTR{<replaceable>filename</replaceable>}</option></term>
- <listitem>
- <para>Match sysfs attribute values of the event device. Trailing
- whitespace in the attribute values is ignored, if the specified match
- value does not contain trailing whitespace itself.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>KERNELS</option></term>
- <listitem>
- <para>Search the devpath upwards for a matching device name.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>SUBSYSTEMS</option></term>
- <listitem>
- <para>Search the devpath upwards for a matching device subsystem name.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>DRIVERS</option></term>
- <listitem>
- <para>Search the devpath upwards for a matching device driver name.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>ATTRS{<replaceable>filename</replaceable>}</option></term>
- <listitem>
- <para>Search the devpath upwards for a device with matching sysfs attribute values.
- If multiple <option>ATTRS</option> matches are specified, all of them
- must match on the same device. Trailing whitespace in the attribute values is ignored,
- if the specified match value does not contain trailing whitespace itself.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>ENV{<replaceable>key</replaceable>}</option></term>
- <listitem>
- <para>Match against a device property value.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>TEST{<replaceable>octal mode mask</replaceable>}</option></term>
- <listitem>
- <para>Test the existence of a file. An octal mode mask can be specified
- if needed.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>PROGRAM</option></term>
- <listitem>
- <para>Execute a program. The key is true, if the program returns
- successfully. The device properties are made available to the
- executed program in the environment. The program's output printed to
- stdout, is available in the RESULT key.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>RESULT</option></term>
- <listitem>
- <para>Match the returned string of the last PROGRAM call. This key can
- be used in the same or in any later rule after a PROGRAM call.</para>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <para>Most of the fields support a shell style pattern matching. The following
- pattern characters are supported:</para>
- <variablelist>
- <varlistentry>
- <term><option>*</option></term>
- <listitem>
- <para>Matches zero, or any number of characters.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>?</option></term>
- <listitem>
- <para>Matches any single character.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>[]</option></term>
- <listitem>
- <para>Matches any single character specified within the brackets. For
- example, the pattern string 'tty[SR]' would match either 'ttyS' or 'ttyR'.
- Ranges are also supported within this match with the '-' character.
- For example, to match on the range of all digits, the pattern [0-9] would
- be used. If the first character following the '[' is a '!', any characters
- not enclosed are matched.</para>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <para>The following keys can get values assigned:</para>
- <variablelist>
- <varlistentry>
- <term><option>NAME</option></term>
- <listitem>
- <para>The name, a network interface should be renamed to, or the name
- a device node should be named. Usually the kernel provides the defined
- node name, or even creates and removes the node before udev receives
- any event. Changing the node name from the kernel's default may result
- in unexpected behavior and is not supported. Udev is only expected to
- handle device node permissions and to create additional symlinks, which
- do not conflict with the kernel device node names.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>SYMLINK</option></term>
- <listitem>
- <para>The name of a symlink targeting the node. Every matching rule will add
- this value to the list of symlinks to be created along with the device node.
- Multiple symlinks may be specified by separating the names by the space
- character. In case multiple devices claim the same name, the link will
- always point to the device with the highest link_priority. If the current device
- goes away, the links will be re-evaluated and the device with the next highest
- link_priority will own the link. If no link_priority is specified, the order
- of the devices, and which of them will own the link, is undefined. Claiming
- the same name for a node and links may result in unexpected behavior and is
- not supported.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>OWNER, GROUP, MODE</option></term>
- <listitem>
- <para>The permissions for the device node. Every specified value overwrites
- the compiled-in default value.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>ATTR{<replaceable>key</replaceable>}</option></term>
- <listitem>
- <para>The value that should be written to a sysfs attribute of the
- event device.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>ENV{<replaceable>key</replaceable>}</option></term>
- <listitem>
- <para>Set a device property value. Property names with a leading '.'
- are not stored in the database or exported to external tool or events.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>TAG</option></term>
- <listitem>
- <para>Attach a tag to a device. This is used to filter events for users
- of libudev's monitor functionality, or to enumerate a group of tagged
- devices. The implementation can only work efficiently if only a few
- tags are attached to a device. It is only meant to be used in
- contexts with specific device filter requirements, and not as a
- general-purpose flag. Excessive use might result in inefficient event
- handling.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>RUN</option></term>
- <listitem>
- <para>Add a program to the list of programs to be executed for a specific
- device. This can only be used for very short running tasks. Running an
- event process for a long period of time may block all further events for
- this or a dependent device. Long running tasks need to be immediately
- detached from the event process itself. If the option
- <option>RUN{<replaceable>fail_event_on_error</replaceable>}</option> is
- specified, and the executed program returns non-zero, the event will be
- marked as failed for a possible later handling.</para>
- <para>If no path is given, the program must be in
- <filename>/lib/udev</filename>, otherwise the full path must be
- specified.</para>
- <para>If the specified string starts with
- <option>socket:<replaceable>path</replaceable></option>, all current event
- values will be passed to the specified socket, as a message in the same
- format the kernel sends an uevent. If the first character of the specified path
- is an @ character, an abstract namespace socket is used, instead of an existing
- socket file.</para>
- <para>Program name and arguments are separated with spaces. To
- include spaces in an argument, use single quotes. Please note
- that this does not run through a shell.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>LABEL</option></term>
- <listitem>
- <para>Named label where a GOTO can jump to.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>GOTO</option></term>
- <listitem>
- <para>Jumps to the next LABEL with a matching name</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>IMPORT{<replaceable>type</replaceable>}</option></term>
- <listitem>
- <para>Import a set of variables as device properties,
- depending on <replaceable>type</replaceable>:</para>
- <variablelist>
- <varlistentry>
- <term><option>program</option></term>
- <listitem>
- <para>Execute an external program specified as the assigned value and
- import its output, which must be in environment key
- format. Path specification, command/argument separation,
- and quoting work like in <option>RUN</option>.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>file</option></term>
- <listitem>
- <para>Import a text file specified as the assigned value, which must be in
- environment key format.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>db</option></term>
- <listitem>
- <para>Import a single property specified as the assigned value from the
- current device database. This works only if the database is already populated
- by an earlier event.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>parent</option></term>
- <listitem>
- <para>Import the stored keys from the parent device by reading
- the database entry of the parent device. The value assigned to
- <option>IMPORT{parent}</option> is used as a filter of key names
- to import (with the same shell-style pattern matching used for
- comparisons).</para>
- </listitem>
- </varlistentry>
- </variablelist>
- <para>If no option is given, udev will choose between <option>program</option>
- and <option>file</option> based on the executable bit of the file
- permissions.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>WAIT_FOR</option></term>
- <listitem>
- <para>Wait for a file to become available or until a 10
- seconds timeout expires.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><option>OPTIONS</option></term>
- <listitem>
- <para>Rule and device options:</para>
- <variablelist>
- <varlistentry>
- <term><option>link_priority=<replaceable>value</replaceable></option></term>
- <listitem>
- <para>Specify the priority of the created symlinks. Devices with higher
- priorities overwrite existing symlinks of other devices. The default is 0.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><option>event_timeout=</option></term>
- <listitem>
- <para>Number of seconds an event will wait for operations to finish, before it
- will terminate itself.</para>
- </listitem>
- </varlistentry>
- <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>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>
- </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, follow the chain of parent devices and use the value
- of the first attribute that matches.
- 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>
- </section>
-</article>
+ <productname>udev</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>udev</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>udev</refname>
+ <refpurpose>Linux dynamic device management</refpurpose>
+ </refnamediv>
+
+ <refsect1><title>Description</title>
+ <para>udev supplies the system software with device events, manages permissions
+ of device nodes and may create additional symlinks in the <filename>/dev</filename>
+ directory, or renames network interfaces. The kernel usually just assigns unpredictable
+ device names based on the order of discovery. Meaningful symlinks or network device
+ names provide a way to reliably identify devices based on their properties or
+ current configuration.</para>
+
+ <para>The udev daemon, <citerefentry><refentrytitle>udevd</refentrytitle>
+ <manvolnum>8</manvolnum></citerefentry>, receives device uevents directly from
+ the kernel whenever a device is added or removed from the system, or it changes its
+ state. When udev receives a device event, it matches its configured set of rules
+ against various device attributes to identify the device. Rules that match may
+ provide additional device information to be stored in the udev database or
+ to be used to create meaningful symlink names.</para>
+
+ <para>All device information udev processes is stored in the udev database and
+ sent out to possible event subscribers. Access to all stored data and the event
+ sources is provided by the library libudev.</para>
+ </refsect1>
+
+ <refsect1><title>Configuration</title>
+ <para>udev configuration files are placed in <filename>/etc/udev/</filename>
+ and <filename>/lib/udev/</filename>. All empty lines or lines beginning with
+ '#' are ignored.</para>
+
+ <refsect2><title>Configuration file</title>
+ <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
+ It consists of a set of variables allowing the user to override default udev values.
+ The following variables can be set:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>udev_root</option></term>
+ <listitem>
+ <para>Specifies where to place the device nodes in the filesystem.
+ The default value is <filename>/dev</filename>.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>udev_log</option></term>
+ <listitem>
+ <para>The logging priority. Valid values are the numerical syslog priorities
+ or their textual representations: <option>err</option>, <option>info</option>
+ and <option>debug</option>.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+
+ <refsect2><title>Rules files</title>
+ <para>The udev rules are read from the files located in the
+ default rules directory <filename>/lib/udev/rules.d/</filename>,
+ the custom rules directory <filename>/etc/udev/rules.d/</filename>
+ and the temporary rules directory <filename>/run/udev/rules.d/</filename>.
+ All rule files are collectively sorted and processed in lexical order,
+ regardless of the directories in which they live. However, files in
+ <filename>/etc/udev/rules.d/</filename> take precedence over files with
+ the same name in <filename>/lib/udev/rules.d/</filename>; this can be
+ used to ignore a default rules file if needed.</para>
+
+ <para>Rule files must have the extension <filename>.rules</filename>; other
+ extensions are ignored.</para>
+
+ <para>Every line in the rules file contains at least one key-value pair.
+ There are two kind of keys: match and assignment.
+ If all match keys are matching against its value, the rule gets applied and the
+ assignment keys get the specified value assigned.</para>
+
+ <para>A matching rule may rename a network interface, add symlinks
+ pointing to the device node, or run a specified program as part of
+ the event handling.</para>
+
+ <para>A rule consists of a comma-separated list of one or more key-value pairs.
+ Each key has a distinct operation, depending on the used operator. Valid
+ operators are:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>==</option></term>
+ <listitem>
+ <para>Compare for equality.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>!=</option></term>
+ <listitem>
+ <para>Compare for inequality.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>=</option></term>
+ <listitem>
+ <para>Assign a value to a key. Keys that represent a list are reset
+ and only this single value is assigned.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>+=</option></term>
+ <listitem>
+ <para>Add the value to a key that holds a list of entries.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>:=</option></term>
+ <listitem>
+ <para>Assign a value to a key finally; disallow any later changes.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>The following key names can be used to match against device properties.
+ Some of the keys also match against properties of the parent devices in sysfs,
+ not only the device that has generated the event. If multiple keys that match
+ a parent device are specified in a single rule, all these keys must match at
+ one and the same parent device.</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>ACTION</option></term>
+ <listitem>
+ <para>Match the name of the event action.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>DEVPATH</option></term>
+ <listitem>
+ <para>Match the devpath of the event device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>KERNEL</option></term>
+ <listitem>
+ <para>Match the name of the event device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>NAME</option></term>
+ <listitem>
+ <para>Match the name of the node or network interface. It can
+ be used once the NAME key has been set in one of the preceding
+ rules.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SYMLINK</option></term>
+ <listitem>
+ <para>Match the name of a symlink targeting the node. It can
+ be used once a SYMLINK key has been set in one of the preceding
+ rules. There may be multiple symlinks; only one needs to match.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SUBSYSTEM</option></term>
+ <listitem>
+ <para>Match the subsystem of the event device.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>DRIVER</option></term>
+ <listitem>
+ <para>Match the driver name of the event device. Only set this key for devices
+ which are bound to a driver at the time the event is generated.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>ATTR{<replaceable>filename</replaceable>}</option></term>
+ <listitem>
+ <para>Match sysfs attribute values of the event device. Trailing
+ whitespace in the attribute values is ignored unless the specified match
+ value itself contains trailing whitespace.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>KERNELS</option></term>
+ <listitem>
+ <para>Search the devpath upwards for a matching device name.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SUBSYSTEMS</option></term>
+ <listitem>
+ <para>Search the devpath upwards for a matching device subsystem name.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>DRIVERS</option></term>
+ <listitem>
+ <para>Search the devpath upwards for a matching device driver name.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>ATTRS{<replaceable>filename</replaceable>}</option></term>
+ <listitem>
+ <para>Search the devpath upwards for a device with matching sysfs attribute values.
+ If multiple <option>ATTRS</option> matches are specified, all of them
+ must match on the same device. Trailing whitespace in the attribute values is ignored
+ unless the specified match value itself contains trailing whitespace.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>ENV{<replaceable>key</replaceable>}</option></term>
+ <listitem>
+ <para>Match against a device property value.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>TAG</option></term>
+ <listitem>
+ <para>Match against a device tag.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>TEST{<replaceable>octal mode mask</replaceable>}</option></term>
+ <listitem>
+ <para>Test the existence of a file. An octal mode mask can be specified
+ if needed.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>PROGRAM</option></term>
+ <listitem>
+ <para>Execute a program to determine whether there
+ is a match; the key is true if the program returns
+ successfully. The device properties are made available to the
+ executed program in the environment. The program's stdout
+ is available in the RESULT key.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>RESULT</option></term>
+ <listitem>
+ <para>Match the returned string of the last PROGRAM call. This key can
+ be used in the same or in any later rule after a PROGRAM call.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>Most of the fields support shell-style pattern matching. The following
+ pattern characters are supported:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>*</option></term>
+ <listitem>
+ <para>Matches zero, or any number of characters.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>?</option></term>
+ <listitem>
+ <para>Matches any single character.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>[]</option></term>
+ <listitem>
+ <para>Matches any single character specified within the brackets. For
+ example, the pattern string 'tty[SR]' would match either 'ttyS' or 'ttyR'.
+ Ranges are also supported within this match with the '-' character.
+ For example, to match on the range of all digits, the pattern [0-9] would
+ be used. If the first character following the '[' is a '!', any characters
+ not enclosed are matched.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>The following keys can get values assigned:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>NAME</option></term>
+ <listitem>
+ <para>The name, a network interface should be renamed to. Or as
+ a temporary workaround, the name a device node should be named.
+ Usually the kernel provides the defined node name, or even creates
+ and removes the node before udev even receives any event. Changing
+ the node name from the kernel's default creates inconsistencies
+ and is not supported. If the kernel and NAME specify different names,
+ an error is logged. Udev is only expected to handle device node
+ permissions and to create additional symlinks, not to change
+ kernel-provided device node names. Instead of renaming a device node,
+ SYMLINK should be used. Symlink names must never conflict with
+ device node names, it results in unpredictable behavior.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SYMLINK</option></term>
+ <listitem>
+ <para>The name of a symlink targeting the node. Every matching rule adds
+ this value to the list of symlinks to be created. Multiple symlinks may be
+ specified by separating the names by the space character. In case multiple
+ devices claim the same name, the link always points to the device with
+ the highest link_priority. If the current device goes away, the links are
+ re-evaluated and the device with the next highest link_priority becomes the owner of
+ the link. If no link_priority is specified, the order of the devices, and
+ which one of them owns the link, is undefined. Claiming the same name for
+ a symlink, which is or might be used for a device node, may result in
+ unexpected behavior and is not supported.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>OWNER, GROUP, MODE</option></term>
+ <listitem>
+ <para>The permissions for the device node. Every specified value overwrites
+ the compiled-in default value.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>ATTR{<replaceable>key</replaceable>}</option></term>
+ <listitem>
+ <para>The value that should be written to a sysfs attribute of the
+ event device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>ENV{<replaceable>key</replaceable>}</option></term>
+ <listitem>
+ <para>Set a device property value. Property names with a leading '.'
+ are not stored in the database or exported to external tool or events.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>TAG</option></term>
+ <listitem>
+ <para>Attach a tag to a device. This is used to filter events for users
+ of libudev's monitor functionality, or to enumerate a group of tagged
+ devices. The implementation can only work efficiently if only a few
+ tags are attached to a device. It is only meant to be used in
+ contexts with specific device filter requirements, and not as a
+ general-purpose flag. Excessive use might result in inefficient event
+ handling.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>RUN</option></term>
+ <listitem>
+ <para>Add a program to the list of programs to be executed for a specific
+ device. This can only be used for very short running tasks. Running an
+ event process for a long period of time may block all further events for
+ this or a dependent device. Long running tasks need to be immediately
+ detached from the event process itself.</para>
+ <para>If no absolute path is given, the program is expected to live in
+ <filename>/lib/udev</filename>, otherwise the absolute path must be
+ specified. Program name and arguments are separated by spaces. Single quotes
+ can be used to specify arguments with spaces.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>LABEL</option></term>
+ <listitem>
+ <para>Named label where a GOTO can jump to.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>GOTO</option></term>
+ <listitem>
+ <para>Jumps to the next LABEL with a matching name</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>IMPORT{<replaceable>type</replaceable>}</option></term>
+ <listitem>
+ <para>Import a set of variables as device properties,
+ depending on <replaceable>type</replaceable>:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>program</option></term>
+ <listitem>
+ <para>Execute an external program specified as the assigned value and
+ import its output, which must be in environment key
+ format. Path specification, command/argument separation,
+ and quoting work like in <option>RUN</option>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>file</option></term>
+ <listitem>
+ <para>Import a text file specified as the assigned value, which must be in
+ environment key format.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>db</option></term>
+ <listitem>
+ <para>Import a single property specified as the assigned value from the
+ current device database. This works only if the database is already populated
+ by an earlier event.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>cmdline</option></term>
+ <listitem>
+ <para>Import a single property from the kernel commandline. For simple flags
+ the value of the property is set to '1'.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>parent</option></term>
+ <listitem>
+ <para>Import the stored keys from the parent device by reading
+ the database entry of the parent device. The value assigned to
+ <option>IMPORT{parent}</option> is used as a filter of key names
+ to import (with the same shell-style pattern matching used for
+ comparisons).</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ <para>If no option is given, udev chooses between <option>program</option>
+ and <option>file</option> based on the executable bit of the file
+ permissions.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>WAIT_FOR</option></term>
+ <listitem>
+ <para>Wait for a file to become available or until a 10
+ seconds timeout expires. The path is relative to the sysfs device,
+ i. e. if no path is specified this waits for an attribute to appear.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>OPTIONS</option></term>
+ <listitem>
+ <para>Rule and device options:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>link_priority=<replaceable>value</replaceable></option></term>
+ <listitem>
+ <para>Specify the priority of the created symlinks. Devices with higher
+ priorities overwrite existing symlinks of other devices. The default is 0.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>event_timeout=</option></term>
+ <listitem>
+ <para>Number of seconds an event waits for operations to finish before
+ giving up and terminating itself.</para>
+ </listitem>
+ </varlistentry>
+ <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 is 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>
~ianmdlvl / elogind.git / blobdiff