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systemd-stable/docs/udev.xml
Kay Sievers c082b99acb remove %e from man page 
Simple %e enumerations never worked reliably outside of udevstart and
udevstart is no longer recommended to use.

Signed-off-by: Kay Sievers <kay.sievers@suse.de>
2005-12-23 00:49:02 +01:00

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<?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.</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_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>$result</option></term>
<listitem>
<para>The string returned by the external program requested with PROGRAM.
A single part of the string, separated by a space character may be selected
by specifying the part number as an attribute: <option>%c{N}</option>.
If the number is followed by the '+' char this part plus all remaining parts
of the result string are substituted: <option>%c{N+}</option></para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>%P</option>, <option>$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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