hwdb(7) — Linux manual page

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.

       Match patterns consist of literal characters, and shell-style
       wildcards:

       •   Asterisk "*" matches any number of characters

       •   Question mark "?"  matches a single character

       •   Character list "[chars]" matches one of the characters chars
           listed between "[" and "]". A range may be specified as with
           a dash as "[first-last]". The match may be inverted with a
           caret "[^...]".

       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

           # The rule above could be also be written in a form that
           # matches Tb, tb, TB, tB:
           mouse:*:name:*[tT]rack[bB]all*:*
            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

           # Match vendor name "Acer" and any product name starting with "X123"
           evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer:pnX123*:*
            KEYBOARD_KEY_a2=wlan

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

       If the hwdb consists of those two files, a keyboard with the
       lookup string
       "evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pnX123"
       will match all three records, and end up with the following
       properties:

           KEYBOARD_KEY_a1=help
           KEYBOARD_KEY_a2=reserved
           KEYBOARD_KEY_a3=battery
           PROPERTY_WITH_SPACES=some string

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 page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2021-08-27.  (At that
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       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 249                                                      HWDB(7)

Pages that refer to this page: sd-hwdb(3)sd_hwdb_get(3)systemd-hwdb(8)