chiark / gitweb /
include <poll.h> instead of <sys/poll.h>
[elogind.git] / man / udev.xml
index 168b1dc..a948ea7 100644 (file)
@@ -1,5 +1,4 @@
-<?xml version='1.0'?>
-<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 
@@ -30,7 +29,7 @@
 
   <refnamediv>
     <refname>udev</refname>
-    <refpurpose>Linux dynamic device management</refpurpose>
+    <refpurpose>Dynamic device management</refpurpose>
   </refnamediv>
 
   <refsect1><title>Description</title>
@@ -41,7 +40,7 @@
     names provide a way to reliably identify devices based on their properties or
     current configuration.</para>
 
-    <para>The udev daemon, <citerefentry><refentrytitle>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_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>
+  <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
+      over files with the same name in <filename>/usr/lib</filename>. This can be
       used to override a system-supplied rules file with a local file if needed;
       a symlink in <filename>/etc</filename> with the same name as a rules file in
-      <filename>/lib</filename>, pointing to <filename>/dev/null</filename>,
-      disables the rules file entirely.</para>
-
-      <para>Rule files must have the extension <filename>.rules</filename>; other
-      extensions are ignored.</para>
+      <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
+      disables the rules file entirely. 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>
+      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>Remove the value from a key that holds a list of entries.</para>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <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
             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>
+            executed program in the environment. The program's standard output
+            is available in the <varname>RESULT</varname> key.</para>
+            <para>This can only be used for very short-running foreground tasks. For details,
+            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>
+            <para>Match the returned string of the last <varname>PROGRAM</varname> call.
+            This key can be used in the same or in any later rule after a
+            <varname>PROGRAM</varname> call.</para>
           </listitem>
         </varlistentry>
       </variablelist>
 
-      <para>Most of the fields support shell-style pattern matching. The following
-      pattern characters are supported:</para>
+      <para>Most of the fields support shell glob pattern matching and
+      alternate patterns. The following special 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.
-            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>
+            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
+            <literal>[0-9]</literal> could be used. If the first character
+            following the <literal>[</literal> is a <literal>!</literal>,
+            any characters not enclosed are matched.</para>
+          </listitem>
+        </varlistentry>
+        <varlistentry>
+          <term><literal>|</literal></term>
+          <listitem>
+            <para>Separates alternative patterns. For example, the pattern string
+            <literal>abc|x*</literal> would match either <literal>abc</literal>
+            or <literal>x*</literal>.</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>
+            <para>The name to use for a network interface. See
+            <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+            for a higher-level mechanism for setting the interface name.
+            The name of a device node 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>SECLABEL{<replaceable>module</replaceable>}</varname></term>
+          <listitem>
+            <para>Applies the specified Linux Security Module label to the device node.</para>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <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>
+            external tools (run by, for example, the <varname>PROGRAM</varname>
+            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>This can only be used for very short running tasks. Running an
+            <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 <filename>/usr/lib/udev</filename>; 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. Starting daemons or other long running processes
-            is not appropriate for udev.</para>
+            this or a dependent device.</para>
+            <para>Starting daemons or other long-running processes is not appropriate
+            for udev; the forked processes, detached or not, will be unconditionally
+            killed after the event handling has finished.</para>
           </listitem>
         </varlistentry>
 
         <varlistentry>
-          <term><option>LABEL</option></term>
+          <term><varname>LABEL</varname></term>
           <listitem>
-            <para>A named label to which a GOTO may jump.</para>
+            <para>A named label to which a <varname>GOTO</varname> 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>
+            <para>Jumps to the next <varname>LABEL</varname> 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
                   <option>IMPORT{parent}</option> is used as a filter of key names
-                  to import (with the same shell-style pattern matching used for
+                  to import (with the same shell glob pattern matching used for
                   comparisons).</para>
                 </listitem>
               </varlistentry>
             </variablelist>
+            <para>This can only be used for very short-running foreground tasks. For details
+            see <option>RUN</option>.</para>
           </listitem>
         </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>
                 </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
               <varlistentry>
                 <term><option>static_node=</option></term>
                 <listitem>
-                  <para>Apply the permissions specified in this rule to the static device node with
-                  the specified name. Static device nodes might be provided by kernel modules
-                  or copied from <filename>/usr/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>
+                  <para>Apply the permissions specified in this rule to the
+                  static device node with the specified name. Also, for every
+                  tag specified in this rule, create a symlink
+                  in the directory
+                  <filename>/run/udev/static_node-tags/<replaceable>tag</replaceable></filename>
+                  pointing at the static device node with the specified name.
+                  Static device node creation is performed by systemd-tmpfiles
+                  before systemd-udevd is started. The static nodes might not
+                  have a corresponding kernel device; they are used to trigger
+                  automatic kernel module loading when they are accessed.</para>
                 </listitem>
               </varlistentry>
               <varlistentry>
                 <term><option>watch</option></term>
                 <listitem>
-                  <para>Watch the device node with inotify; when the node is closed after being opened for
-                  writing, a change uevent is synthesized.</para>
+                  <para>Watch the device node with inotify; when the node is
+                  closed after being opened for writing, a change uevent is
+                  synthesized.</para>
                 </listitem>
               </varlistentry>
               <varlistentry>
         </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>
-      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>
+      <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 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>
 
         <varlistentry>
           <term><option>$id</option>, <option>%b</option></term>
           <listitem>
-            <para>The name of the device matched while searching the devpath upwards for
-              <option>SUBSYSTEMS</option>, <option>KERNELS</option>, <option>DRIVERS</option> and <option>ATTRS</option>.
+            <para>The name of the device matched while searching the devpath
+              upwards for <option>SUBSYSTEMS</option>, <option>KERNELS</option>,
+              <option>DRIVERS</option>, and <option>ATTRS</option>.
             </para>
           </listitem>
         </varlistentry>
         <varlistentry>
           <term><option>$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>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>
           <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, then the attribute from that
-            parent device is used.</para>
-            <para>If the attribute is a symlink, the last element of the symlink target is
-            returned as the value.</para>
+              all keys of the rule have matched. If the matching device does not
+              have such an attribute, and a previous <option>KERNELS</option>,
+              <option>SUBSYSTEMS</option>, <option>DRIVERS</option>, or
+              <option>ATTRS</option> test selected a parent device, then the
+              attribute from that parent device is used.
+            </para>
+            <para>If the attribute is a symlink, the last element of the
+              symlink target is returned as the value.
+            </para>
           </listitem>
         </varlistentry>
 
         <varlistentry>
           <term><option>$result</option>, <option>%c</option></term>
           <listitem>
-            <para>The string returned by the external program requested with PROGRAM.
+            <para>The string returned by the external program requested with
+            <varname>PROGRAM</varname>.
             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>udevd</refentrytitle><manvolnum>8</manvolnum>
+    <para>
+      <citerefentry>
+        <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
       </citerefentry>,
       <citerefentry>
         <refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum>
-    </citerefentry></para>
+      </citerefentry>,
+      <citerefentry>
+        <refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum>
+      </citerefentry>
+    </para>
   </refsect1>
 </refentry>