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88 lines
3.9 KiB
XML
88 lines
3.9 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="hwdb" conditional="ENABLE_HWDB">
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<refentryinfo>
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<title>hwdb</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Kay</firstname>
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<surname>Sievers</surname>
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<email>kay@vrfy.org</email>
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</author>
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<author>
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<contrib>Developer</contrib>
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<firstname>Tom</firstname>
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<surname>Gundersen</surname>
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<email>teg@jklm.no</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>hwdb</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>hwdb</refname>
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<refpurpose>Hardware Database</refpurpose>
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</refnamediv>
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<refsect1><title>Description</title>
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<para>The hardware database is a key-value store for associating modalias-like keys to
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udev-properties-like values. It is used primarily by udev to add the relevant properties
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to matching devices, but it can also be queried directly.</para>
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</refsect1>
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<refsect1><title>Hardware Database Files</title>
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<para>The hwdb files are read from the files located in the
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system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename>,
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the volatile runtime directory <filename>/run/udev/hwdb.d</filename>
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and the local administration directory <filename>/etc/udev/hwdb.d</filename>.
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All hwdb files are collectively sorted and processed in lexical order,
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regardless of the directories in which they live. However, files with
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identical filenames replace each other. Files in <filename>/etc</filename>
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have the highest priority, files in <filename>/run</filename> take precedence
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over files with the same name in <filename>/usr/lib</filename>. This can be
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used to override a system-supplied hwdb file with a local file if needed;
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a symlink in <filename>/etc</filename> with the same name as a hwdb file in
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<filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
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disables the hwdb file entirely. hwdb files must have the extension
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<filename>.hwdb</filename>; other extensions are ignored.</para>
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<para>The hwdb file contains data records consisting of matches and
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associated key-value pairs. Every record in the hwdb starts with one or
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more match string, specifying a shell glob to compare the database
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lookup string against. Multiple match lines are specified in additional
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consecutive lines. Every match line is compared indivdually, they are
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combined by OR. Every match line must start at the first character of
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the line.</para>
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<para>The match lines are followed by one or more key-value pair lines, which
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are recognized by a leading space character. The key name and value are separated
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by <literal>=</literal>. An empty line signifies the end
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of a record. Lines beginning with <literal>#</literal> are ignored.</para>
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<para>The content of all hwdb files is read by
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<citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
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or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the compiled
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database in an immutable image.
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During runtime only the binary database is used.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry>
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<refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum>
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</citerefentry>
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</para>
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</refsect1>
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</refentry>
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