- <refsect1><title>Hardware Database Files</title>
- <para>The hwdb files are read from the files located in the
- system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename>,
- the volatile runtime directory <filename>/run/udev/hwdb.d</filename>
- and the local administration directory <filename>/etc/udev/hwdb.d</filename>.
- All hwdb files are collectively sorted and processed in lexical order,
- regardless of the directories in which they live. However, files with
- 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>/usr/lib</filename>. This can be
- used to override a system-supplied hwdb file with a local file if needed;
- a symlink in <filename>/etc</filename> with the same name as a hwdb file in
- <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
- disables the hwdb file entirely. hwdb files must have the extension
- <filename>.hwdb</filename>; other extensions are ignored.</para>
-
- <para>The hwdb file contains data records consisting of matches and
- associated key-value pairs. Every record in the hwdb starts with one or
- more match string, specifying a shell glob to compare the database
- lookup string against. Multiple match lines are specified in additional
- consecutive lines. Every match line is compared indivdually, they are
- combined by OR. Every match line must start at the first character of
- the line.</para>
-
- <para>The match lines are followed by one or more key-value pair lines, which
- are recognized by a leading space character. The key name and value are separated
- by <literal>=</literal>. An empty line signifies the end
- of a record. Lines beginning with <literal>#</literal> are ignored.</para>
-
- <para>The content of all hwdb files is read by
- <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>.
- During runtime only the binary database is used.</para>
- </refsect1>
-