<refsect2><title>Rules files</title>
<para>The udev rules are read from the files located in the
- default rules directory <filename>/lib/udev/rules.d/</filename>,
- the custom rules directory <filename>/etc/udev/rules.d/</filename>
- and the temporary rules directory <filename>/run/udev/rules.d/</filename>.
- All rule files are collectively sorted and processed in lexical order,
- regardless of the directories in which they live. However, files in
- <filename>/etc/udev/rules.d/</filename> take precedence over files with
- the same name in <filename>/lib/udev/rules.d/</filename>; this can be
- used to ignore a default rules file if needed.</para>
+ system rules directory <filename>/lib/udev/rules.d/</filename>,
+ the local administration directory <filename>/etc/udev/rules.d/</filename>
+ and the volatile runtime directory <filename>/run/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>/run</filename>
+ have the highest priority, files in <filename>/etc</filename> take precedence
+ over files with the same name in <filename>/lib</filename>. This can be
+ used to overwrite a system rules 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>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>TAGS</option></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>
<listitem>
</listitem>
</varlistentry>
</variablelist>
- <para>If no option is given, udev chooses between <option>program</option>
- and <option>file</option> based on the executable bit of the file
- permissions.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>watch</option></term>
<listitem>
- <para>Watch the device node with inotify; when closed after being opened for
- writing, a change uevent is synthesised.</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>
<para>The <option>NAME</option>, <option>SYMLINK</option>, <option>PROGRAM</option>,
<option>OWNER</option>, <option>GROUP</option>, <option>MODE</option> and <option>RUN</option>
- fields support simple printf-like string substitutions. The <option>RUN</option>
- format chars gets applied after all rules have been processed, right before the program
- is executed. It allows the use of device properties set by earlier matching
- rules. For all other fields, substitutions are applied while the individual rule is
+ 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>
<varlistentry>
<para>The value of a sysfs attribute found at the device where
all keys of the rule have matched. If the matching device does not have
such an attribute, and a previous KERNELS, SUBSYSTEMS, DRIVERS, or
- ATTRS test selected a parent device, use the attribute from that
- parent device.
- If the attribute is a symlink, the last element of the symlink target is
+ 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>
</listitem>
</varlistentry>
<term><option>$result</option>, <option>%c</option></term>
<listitem>
<para>The string returned by the external program requested with PROGRAM.
- A single part of the string, separated by a space character may be selected
+ A single part of the string, separated by a space character, may be selected
by specifying the part number as an attribute: <option>%c{N}</option>.
- If the number is followed by the '+' char this part plus all remaining parts
+ If the number is followed by the '+' character, this part plus all remaining parts
of the result string are substituted: <option>%c{N+}</option></para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>$links</option></term>
<listitem>
- <para>The current list of symlinks, separated by a space character. The value is
- only set if an earlier rule assigned a value, or during a remove events.</para>
+ <para>A space-separated list of the current symlinks. The value is
+ only set during a remove event or if an earlier rule assigned a value.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>$tempnode</option>, <option>%N</option></term>
<listitem>
- <para>The name of a created temporary device node to provide access to
+ <para>The name of a temporary device node created to provide access to
the device from a external program before the real node is created.</para>
</listitem>
</varlistentry>
~ianmdlvl / elogind.git / blobdiff