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+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<refentry id="hwdb">
+ <refentryinfo>
+ <title>hwdb</title>
+ <productname>systemd</productname>
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Kay</firstname>
+ <surname>Sievers</surname>
+ <email>kay@vrfy.org</email>
+ </author>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Tom</firstname>
+ <surname>Gundersen</surname>
+ <email>teg@jklm.no</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>hwdb</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>hwdb</refname>
+ <refpurpose>Hardware Database</refpurpose>
+ </refnamediv>
+
+ <refsect1><title>Description</title>
+ <para>The hardware database is a key-value store for associating modalias-like keys to
+ udev-properties-like values. It is used primarily by udev to add the relevant properties
+ to matching devices, but it can also be queried directly.</para>
+ </refsect1>
+
+ <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>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
+ or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the compiled
+ database in an immutable image.
+ During runtime only the binary database is used.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry>
+ <refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum>
+ </citerefentry>
+ </para>
+ </refsect1>
+</refentry>