+<?xml version='1.0'?>
+<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<article>
+ <articleinfo>
+ <title>xmlto</title>
+ <author>
+ <firstname>Kay</firstname>
+ <surname>Sievers</surname>
+ <email>kay.sievers@vrfy.org</email>
+ </author>
+ <copyright>
+ <year>2005</year>
+ <holder>Kay Sievers</holder>
+ </copyright>
+ </articleinfo>
+
+ <section>
+ <title>udev</title>
+ <refentry>
+ <refentryinfo>
+ <title>udev</title>
+ <date>August 2005</date>
+ <productname>udev</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>udev</refentrytitle>
+ <manvolnum>8</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 form the system. The program
+ <command>udev</command> itself may be used as an event handler in situations,
+ where running the daemon is not appropriate, like in initramfs.</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>All udev configuration files are placed in <filename>/etc/udev/*</filename>.
+ Every file consist of a set of lines of text. 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_db</option></term>
+ <listitem>
+ <para>The name and location of the udev database. The default value is
+ <filename>/dev/.udevdb</filename>.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>udev_rules</option></term>
+ <listitem>
+ <para>The name of the udev rules file or directory to look for files
+ with the suffix <filename>.rules</filename>. Multiple rule files are
+ read in lexical order. The default value is
+ <filename>/etc/udev/rules.d</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
+ <filename>/etc/udev/rules.d</filename> directory or at the location specified
+ value in the configuraton file. Every line in the rules file contains at least
+ one key value pair. There are two kind of keys, match and assignement keys.
+ If all match keys are matching against its value, the rule gets applied and the
+ assign keys get the specified value assigned. 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 may 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 non-equality.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>=</option></term>
+ <listitem>
+ <para>Asign 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:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>ACTION</option></term>
+ <listitem>
+ <para>Match the kernel action name.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>KERNEL</option></term>
+ <listitem>
+ <para>Match the kernel device name</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>DEVPATH</option></term>
+ <listitem>
+ <para>Match the kernel devpath.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SUBSYSTEM</option></term>
+ <listitem>
+ <para>Match the kernel subsystem name</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>BUS</option></term>
+ <listitem>
+ <para>Match the typ of bus the device is connected to.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>DRIVER</option></term>
+ <listitem>
+ <para>Match the kernel driver name.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>ID</option></term>
+ <listitem>
+ <para>Match the device number on the bus.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>ENV{<replaceable>key</replaceable>}</option></term>
+ <listitem>
+ <para>Match against the value of an environment key. Depending on
+ the specified operation, this key is also used as a assignment.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SYSFS{<replaceable>filename</replaceable>}</option></term>
+ <listitem>
+ <para>Match the sysfs attribute value. Up to five values can be specified.
+ Trailing whitespace is ignored, if the specified match value does not contain
+ trailing whitespace itself.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>PROGRAM</option></term>
+ <listitem>
+ <para>Execute external program. The key is true, if the program returns
+ without exit code zero. The whole event environment is available to the
+ executed program. The program's output printed to stdout is available for
+ 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.
+ 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 of the node to be created, or the name, the network interface
+ should be renamed to. Only one rule can set the a name, all later rules with
+ a NAME key will be ignored.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SYMLINK</option></term>
+ <listitem>
+ <para>The name of a symlink targeting the node. Every matching rule can 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.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>OWNER, GROUP, MODE</option></term>
+ <listitem>
+ <para>The permissions for the device node. Every specified value over writes
+ the compiled-in default value.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>ENV{<replaceable>key</replaceable>}</option></term>
+ <listitem>
+ <para>Export the key to the environment. Depending on the specified
+ operation, this key is also used as a match.</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.</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 gname</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>IMPORT{<replaceable>type</replaceable>}</option></term>
+ <listitem>
+ <para>Import the printed result or the content of a file in environment key
+ format into the event environment. <option>program</option> will execute an
+ external program and read its output. <option>file</option> will inport a
+ text file. If no option is given, udev will determine it from the executable
+ bit of of the file permissions.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>WAIT_FOR_SYSFS</option></term>
+ <listitem>
+ <para>Wait for the specified sysfs file of the device to be created. May be used
+ to fight agains timing issues wth the kernel.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>OPTIONS</option></term>
+ <listitem>
+ <para><option>last_rule</option> stops further rules application. No later rules
+ will have any effect.
+ <option>ignore_device</option> will ignore this event completely.
+ <option>ignore_remove</option> will ignore any later remove event for this
+ device. This may be useful as a workaround for broken device drivers.
+ <option>all_partitions</option> will create device nodes for all available partitions of
+ a block device. This may be useful for removable media.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>The <option>NAME</option>, <option>SYMLINK</option>, <option>PROGRAM</option>,
+ <option>OWNER</option> and <option>GROUP</option> fields support simple
+ printf-like string substitutions:</para>
+ <variablelist>
+ <varlistentry>
+ <term><option>%k</option>, <option>$kernel</option></term>
+ <listitem>
+ <para>The kernel name for this device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%b</option>, <option>$id</option></term>
+ <listitem>
+ <para>The kernel bus id for this device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%n</option>, <option>$number</option></term>
+ <listitem>
+ <para>The kernel number for this device. For example, 'sda3' has
+ kernel number of '3'</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%p</option>, <option>$devpath</option></term>
+ <listitem>
+ <para>The devpath of the device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%s{<replaceable>file</replaceable>}</option>, <option>$sysfs{<replaceable>file</replaceable>}</option></term>
+ <listitem>
+ <para>The content of a sysfs attribute.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%e{<replaceable>key</replaceable>}</option>, <option>$env{<replaceable>key</replaceable>}</option></term>
+ <listitem>
+ <para>The value of an environment variable.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%m</option>, <option>$major</option></term>
+ <listitem>
+ <para>The kernel major number for the device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%M</option> <option>$minor</option></term>
+ <listitem>
+ <para>The kernel minor number for the device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%c</option>, <option>$result</option></term>
+ <listitem>
+ <para>The string returned by the external program requested with PROGRAM.
+ A single part of the string, separated by a space character may be selected
+ by specifying the part number as an attribute: <option>%c{N}</option>.
+ If the number is followed by the '+' char this part plus all remaining parts
+ of the result string are substituted: <option>%c{N+}</option></para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%e</option>, <option>$enum</option></term>
+ <listitem>
+ <para>If a device node already exists with the name, the smallest next free
+ number is used. This can be used to create compatibility symlinks and enumerate
+ devices of the same type originating from different kernel subsystems.</para>
+ <para>Note: The use of the enumeration facility is unreliable for events that
+ request a number at the same time. The use of enumerations in todays setups
+ where devices can come and go at any time is not recomended.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%P</option>, <option>$parent</option></term>
+ <listitem>
+ <para>The node name of the parent device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%r</option>, <option>$root</option></term>
+ <listitem>
+ <para>The udev_root value.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>%N</option>, <option>$tempnode</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>
+ <para>The count of characters to be substituted may be limited by specifying
+ the format length value. For example, '%3s{file}' will only
+ insert the first three characters of the sysfs attribute</para>
+ </refsect2>
+ </refsect1>
+
+ <refsect1><title>ENVIRONMENT</title>
+ <variablelist>
+ <varlistentry>
+ <term><option>ACTION</option></term>
+ <listitem>
+ <para><replaceable>add</replaceable> or <replaceable>remove</replaceable> signifies
+ the addition or the removal of a device.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>DEVPATH</option></term>
+ <listitem>
+ <para>The sysfs devpath without the mountpoint but a leading slash.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>SUBSYSTEM</option></term>
+ <listitem>
+ <para>The kernel subsystem the device belongs to.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>UDEV_LOG</option></term>
+ <listitem>
+ <para>Overrides the syslog priority specified in the config file.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </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 <email>dsteklof@us.ibm.com</email> and many others.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>SEE ALSO</title>
+ <para><citerefentry>
+ <refentrytitle>udev</refentrytitle><manvolnum>8</manvolnum>
+ </citerefentry>,
+ <citerefentry>
+ <refentrytitle>udevinfo</refentrytitle><manvolnum>8</manvolnum>
+ </citerefentry>,
+ <citerefentry>
+ <refentrytitle>udevd</refentrytitle><manvolnum>8</manvolnum>
+ </citerefentry>,
+ <citerefentry>
+ <refentrytitle>udevmonitor</refentrytitle><manvolnum>8</manvolnum>
+ </citerefentry></para>
+ </refsect1>
+ </refentry>
+ </section>
+</article>
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