NAME | DESCRIPTION | HARDWARE DATABASE FILES | EXAMPLES | SEE ALSO | COLOPHON

HWDB(7)                             hwdb                             HWDB(7)

NAME         top

       hwdb - Hardware Database

DESCRIPTION         top

       The hardware database is a key-value store for associating
       modalias-like keys to udev-property-like values. It is used primarily
       by udev to add the relevant properties to matching devices, but it
       can also be queried directly.

HARDWARE DATABASE FILES         top

       The hwdb files are read from the files located in the system hwdb
       directory /usr/lib/udev/hwdb.d and the local administration directory
       /etc/udev/hwdb.d. 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 /etc have the highest priority and take precedence
       over files with the same name in /usr/lib. This can be used to
       override a system-supplied hwdb file with a local file if needed; a
       symlink in /etc with the same name as a hwdb file in /usr/lib,
       pointing to /dev/null, disables that hwdb file entirely. hwdb files
       must have the extension .hwdb; other extensions are ignored.

       Each hwdb file contains data records consisting of matches and
       associated key-value pairs. Every record in the hwdb starts with one
       or more match strings, specifying a shell glob to compare the lookup
       string against. Multiple match lines are specified in consecutive
       lines. Every match line is compared individually, and they are
       combined by OR. Every match line must start at the first character of
       the line.

       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 "=". An empty line signifies the end of a
       record. Lines beginning with "#" are ignored.

       In case multiple records match a given lookup string, the key-value
       pairs from all records are combined. If a key is specified multiple
       times, the value from the record with the highest priority is used
       (each key can have only a single value). The priority is higher when
       the record is in a file that sorts later lexicographically, and in
       case of records in the same file, later records have higher priority.

       The content of all hwdb files is read by systemd-hwdb(8) and compiled
       to a binary database located at /etc/udev/hwdb.bin, or alternatively
       /usr/lib/udev/hwdb.bin if you want ship the compiled database in an
       immutable image. During runtime, only the binary database is used.

EXAMPLES         top

       Example 1. General syntax of hwdb files

           # /usr/lib/udev/hwdb.d/example.hwdb
           # Comments can be placed before any records. This is a good spot
           # to describe what that file is used for, what kind of properties
           # it defines, and the ordering convention.

           # A record with three matches and one property
           mouse:*:name:*Trackball*:
           mouse:*:name:*trackball*:
           mouse:*:name:*TrackBall*:
            ID_INPUT_TRACKBALL=1

           # A record with a single match and five properties
           mouse:usb:v046dp4041:name:Logitech MX Master:
            MOUSE_DPI=1000@166
            MOUSE_WHEEL_CLICK_ANGLE=15
            MOUSE_WHEEL_CLICK_ANGLE_HORIZONTAL=26
            MOUSE_WHEEL_CLICK_COUNT=24
            MOUSE_WHEEL_CLICK_COUNT_HORIZONTAL=14

       Example 2. Overriding of properties

           # /usr/lib/udev/hwdb.d/60-keyboard.hwdb
           evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*
            KEYBOARD_KEY_a1=help
            KEYBOARD_KEY_a2=setup
            KEYBOARD_KEY_a3=battery

           evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn123*
            KEYBOARD_KEY_a2=wlan

           # /etc/udev/hwdb.d/70-keyboard.hwdb
           # disable wlan key on all at keyboards
           evdev:atkbd:*
            KEYBOARD_KEY_a2=reserved

       If the hwdb consists of those two files, a keyboard with the lookup
       string "evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pn123"
       will match all three records, and end up with the following
       properties:

           KEYBOARD_KEY_a1=help
           KEYBOARD_KEY_a2=reserved
           KEYBOARD_KEY_a3=battery

SEE ALSO         top

       systemd-hwdb(8)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see 
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
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       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

systemd 233                                                          HWDB(7)

Pages that refer to this page: systemd.directives(7)systemd.index(7)systemd-hwdb(8)