names provide a way to reliably identify devices based on their properties or
current configuration.</para>
- <para>The udev daemon, <citerefentry><refentrytitle>systemd-udevd</refentrytitle>
+ <para>The udev daemon, <citerefentry><refentrytitle>systemd-udevd.service</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
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>/usr/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_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>
+ <refsect1><title>Rules files</title>
<para>The udev rules are read from the files located in the
system rules directory <filename>/usr/lib/udev/rules.d</filename>,
the volatile runtime directory <filename>/run/udev/rules.d</filename>
and the local administration directory <filename>/etc/udev/rules.d</filename>.
All rules files are collectively sorted and processed in lexical order,
regardless of the directories in which they live. However, files with
- identical file names replace each other. Files in <filename>/etc</filename>
+ identical filenames replace each other. Files in <filename>/etc</filename>
have the highest priority, files in <filename>/run</filename> take precedence
over files with the same name in <filename>/lib</filename>. This can be
used to override a system-supplied rules file with a local file if needed;
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>
+ Except for empty lines or lines beginning with <literal>#</literal>, which are ignored.
+ There are two kinds of keys: match and assignment.
+ If all match keys match against their values, the rule gets applied and the
+ assignment keys get the specified values 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
operators are:</para>
<variablelist>
<varlistentry>
- <term><option>==</option></term>
+ <term><literal>==</literal></term>
<listitem>
<para>Compare for equality.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>!=</option></term>
+ <term><literal>!=</literal></term>
<listitem>
<para>Compare for inequality.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>=</option></term>
+ <term><literal>=</literal></term>
<listitem>
<para>Assign a value to a key. Keys that represent a list are reset
and only this single value is assigned.</para>
</varlistentry>
<varlistentry>
- <term><option>+=</option></term>
+ <term><literal>+=</literal></term>
<listitem>
<para>Add the value to a key that holds a list of entries.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>:=</option></term>
+ <term><literal>:=</literal></term>
<listitem>
<para>Assign a value to a key finally; disallow any later changes.</para>
</listitem>
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>
+ <variablelist class='udev-directives'>
<varlistentry>
- <term><option>ACTION</option></term>
+ <term><varname>ACTION</varname></term>
<listitem>
<para>Match the name of the event action.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>DEVPATH</option></term>
+ <term><varname>DEVPATH</varname></term>
<listitem>
<para>Match the devpath of the event device.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>KERNEL</option></term>
+ <term><varname>KERNEL</varname></term>
<listitem>
<para>Match the name of the event device.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>NAME</option></term>
+ <term><varname>NAME</varname></term>
<listitem>
<para>Match the name of a network interface. It can be used once the
NAME key has been set in one of the preceding rules.</para>
</varlistentry>
<varlistentry>
- <term><option>SYMLINK</option></term>
+ <term><varname>SYMLINK</varname></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
</varlistentry>
<varlistentry>
- <term><option>SUBSYSTEM</option></term>
+ <term><varname>SUBSYSTEM</varname></term>
<listitem>
<para>Match the subsystem of the event device.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>DRIVER</option></term>
+ <term><varname>DRIVER</varname></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>
+ <term><varname>ATTR{<replaceable>filename</replaceable>}</varname></term>
<listitem>
<para>Match sysfs attribute values of the event device. Trailing
whitespace in the attribute values is ignored unless the specified match
</varlistentry>
<varlistentry>
- <term><option>KERNELS</option></term>
+ <term><varname>KERNELS</varname></term>
<listitem>
<para>Search the devpath upwards for a matching device name.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>SUBSYSTEMS</option></term>
+ <term><varname>SUBSYSTEMS</varname></term>
<listitem>
<para>Search the devpath upwards for a matching device subsystem name.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>DRIVERS</option></term>
+ <term><varname>DRIVERS</varname></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>
+ <term><varname>ATTRS{<replaceable>filename</replaceable>}</varname></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
+ If multiple <varname>ATTRS</varname> 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>TAGS</option></term>
+ <term><varname>TAGS</varname></term>
<listitem>
<para>Search the devpath upwards for a device with matching tag.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>ENV{<replaceable>key</replaceable>}</option></term>
+ <term><varname>ENV{<replaceable>key</replaceable>}</varname></term>
<listitem>
<para>Match against a device property value.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>TAG</option></term>
+ <term><varname>TAG</varname></term>
<listitem>
<para>Match against a device tag.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>TEST{<replaceable>octal mode mask</replaceable>}</option></term>
+ <term><varname>TEST{<replaceable>octal mode mask</replaceable>}</varname></term>
<listitem>
<para>Test the existence of a file. An octal mode mask can be specified
if needed.</para>
</varlistentry>
<varlistentry>
- <term><option>PROGRAM</option></term>
+ <term><varname>PROGRAM</varname></term>
<listitem>
<para>Execute a program to determine whether there
is a match; the key is true if the program returns
executed program in the environment. The program's stdout
is available in the RESULT key.</para>
<para>This can only be used for very short-running foreground tasks. For details
- see <option>RUN</option>.</para>
+ see <varname>RUN</varname>.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>RESULT</option></term>
+ <term><varname>RESULT</varname></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>
pattern characters are supported:</para>
<variablelist>
<varlistentry>
- <term><option>*</option></term>
+ <term><literal>*</literal></term>
<listitem>
<para>Matches zero or more characters.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>?</option></term>
+ <term><literal>?</literal></term>
<listitem>
<para>Matches any single character.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>[]</option></term>
+ <term><literal>[]</literal></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 via the '-' character.
+ example, the pattern string <literal>tty[SR]</literal>
+ would match either <literal>ttyS</literal> or <literal>ttyR</literal>.
+ Ranges are also supported via the <literal>-</literal> character.
For example, to match on the range of all digits, the pattern [0-9] could
- be used. If the first character following the '[' is a '!', any characters
- not enclosed are matched.</para>
+ be used. If the first character following the <literal>[</literal> is a
+ <literal>!</literal>, any characters not enclosed are matched.</para>
</listitem>
</varlistentry>
</variablelist>
<para>The following keys can get values assigned:</para>
- <variablelist>
+ <variablelist class='udev-directives'>
<varlistentry>
- <term><option>NAME</option></term>
+ <term><varname>NAME</varname></term>
<listitem>
<para>The name to use for a network interface. The name of a device node
- can not be changed by udev, only additional symlinks can be created.</para>
+ cannot be changed by udev, only additional symlinks can be created.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>SYMLINK</option></term>
+ <term><varname>SYMLINK</varname></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. Also, symlink names must
- never conflict with the kernel's default device node names, as that would
- result in unpredictable behavior.
+ this value to the list of symlinks to be created.</para>
+ <para>The set of characters to name a symlink is limited. Allowed
+ characters are <literal>0-9A-Za-z#+-.:=@_/</literal>, valid UTF-8 character
+ sequences, and <literal>\x00</literal> hex encoding. All other
+ characters are replaced by a <literal>_</literal> character.</para>
+ <para>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.</para>
+ <para>Symlink names must never conflict with the kernel's default device
+ node names, as that would result in unpredictable behavior.
</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>OWNER, GROUP, MODE</option></term>
+ <term><varname>OWNER</varname>, <varname>GROUP</varname>, <varname>MODE</varname></term>
<listitem>
<para>The permissions for the device node. Every specified value overrides
the compiled-in default value.</para>
</varlistentry>
<varlistentry>
- <term><option>ATTR{<replaceable>key</replaceable>}</option></term>
+ <term><varname>ATTR{<replaceable>key</replaceable>}</varname></term>
<listitem>
<para>The value that should be written to a sysfs attribute of the
event device.</para>
</varlistentry>
<varlistentry>
- <term><option>ENV{<replaceable>key</replaceable>}</option></term>
+ <term><varname>ENV{<replaceable>key</replaceable>}</varname></term>
<listitem>
- <para>Set a device property value. Property names with a leading '.'
+ <para>Set a device property value. Property names with a leading <literal>.</literal>
are neither stored in the database nor exported to events or
external tools (run by, say, the PROGRAM match key).</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>TAG</option></term>
+ <term><varname>TAG</varname></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
</varlistentry>
<varlistentry>
- <term><option>RUN</option></term>
+ <term><varname>RUN{<replaceable>type</replaceable>}</varname></term>
<listitem>
- <para>Add a program to the list of programs to be executed for a specific
- device.</para>
- <para>If no absolute path is given, the program is expected to live in
- /usr/lib/udev, otherwise the absolute path must be specified. The program
- name and following arguments are separated by spaces. Single quotes can
- be used to specify arguments with spaces.</para>
+ <para>Add a program to the list of programs to be executed after processing all the
+ rules for a specific event, depending on <literal>type</literal>:</para>
+ <variablelist>
+ <varlistentry>
+ <term><literal>program</literal></term>
+ <listitem>
+ <para>Execute an external program specified as the assigned
+ value. If no absolute path is given, the program is expected to live in
+ /usr/lib/udev, otherwise the absolute path must be specified.</para>
+ <para>This is the default if no <replaceable>type</replaceable> is
+ specified.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><literal>builtin</literal></term>
+ <listitem>
+ <para>As <varname>program</varname>, but use one of the built-in programs rather
+ than an external one.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ <para>The program name and following arguments are separated by spaces.
+ Single quotes can be used to specify arguments with spaces.</para>
<para>This can only be used for very short-running foreground tasks. Running an
event process for a long period of time may block all further events for
this or a dependent device.</para>
</varlistentry>
<varlistentry>
- <term><option>LABEL</option></term>
+ <term><varname>LABEL</varname></term>
<listitem>
<para>A named label to which a GOTO may jump.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>GOTO</option></term>
+ <term><varname>GOTO</varname></term>
<listitem>
<para>Jumps to the next LABEL with a matching name.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>IMPORT{<replaceable>type</replaceable>}</option></term>
+ <term><varname>IMPORT{<replaceable>type</replaceable>}</varname></term>
<listitem>
<para>Import a set of variables as device properties,
- depending on <replaceable>type</replaceable>:</para>
+ depending on <literal>type</literal>:</para>
<variablelist>
<varlistentry>
- <term><option>program</option></term>
+ <term><literal>program</literal></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>
+ and quoting work like in <varname>RUN</varname>.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>file</option></term>
+ <term><literal>builtin</literal></term>
+ <listitem>
+ <para>Similar to <literal>program</literal>, but use one of the
+ built-in programs rather than an external one.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><literal>file</literal></term>
<listitem>
<para>Import a text file specified as the assigned value, the content
of which must be in environment key format.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>db</option></term>
+ <term><literal>db</literal></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
</listitem>
</varlistentry>
<varlistentry>
- <term><option>cmdline</option></term>
+ <term><literal>cmdline</literal></term>
<listitem>
<para>Import a single property from the kernel command line. For simple flags
- the value of the property is set to '1'.</para>
+ the value of the property is set to <literal>1</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>parent</option></term>
+ <term><literal>parent</literal></term>
<listitem>
<para>Import the stored keys from the parent device by reading
the database entry of the parent device. The value assigned to
</varlistentry>
<varlistentry>
- <term><option>WAIT_FOR</option></term>
+ <term><varname>WAIT_FOR</varname></term>
<listitem>
<para>Wait for a file to become available or until a timeout of
10 seconds expires. The path is relative to the sysfs device;
</varlistentry>
<varlistentry>
- <term><option>OPTIONS</option></term>
+ <term><varname>OPTIONS</varname></term>
<listitem>
<para>Rule and device options:</para>
- <variablelist>
+ <variablelist class='udev-directives'>
<varlistentry>
<term><option>link_priority=<replaceable>value</replaceable></option></term>
<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 string substitutions. The <option>RUN</option>
+ <para>The <varname>NAME</varname>, <varname>SYMLINK</varname>, <varname>PROGRAM</varname>,
+ <varname>OWNER</varname>, <varname>GROUP</varname>, <varname>MODE</varname> and <varname>RUN</varname>
+ fields support simple string substitutions. The <varname>RUN</varname>
substitutions are performed after all rules have been processed, right before the program
is executed, allowing for the use of device properties set by earlier matching
rules. For all other fields, substitutions are performed while the individual rule is
being processed. The available substitutions are:</para>
- <variablelist>
+ <variablelist class='udev-directives'>
<varlistentry>
<term><option>$kernel</option>, <option>%k</option></term>
<listitem>
<varlistentry>
<term><option>$number</option>, <option>%n</option></term>
<listitem>
- <para>The kernel number for this device. For example, 'sda3' has
- kernel number of '3'</para>
+ <para>The kernel number for this device. For example,
+ <literal>sda3</literal> has kernel number <literal>3</literal>.</para>
</listitem>
</varlistentry>
<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 '+' character, this part plus all remaining parts
- of the result string are substituted: <option>%c{N+}</option></para>
+ by specifying the part number as an attribute: <literal>%c{N}</literal>.
+ If the number is followed by the <literal>+</literal> character, this part plus all remaining parts
+ of the result string are substituted: <literal>%c{N+}</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>%%</option></term>
<listitem>
- <para>The '%' character itself.</para>
+ <para>The <literal>%</literal> character itself.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>$$</option></term>
<listitem>
- <para>The '$' character itself.</para>
+ <para>The <literal>$</literal> character itself.</para>
</listitem>
</varlistentry>
</variablelist>
- </refsect2>
</refsect1>
<refsect1>
<title>See Also</title>
<para><citerefentry>
- <refentrytitle>systemd-udevd</refentrytitle><manvolnum>8</manvolnum>
+ <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
~ianmdlvl / elogind.git / blobdiff