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NAME | DESCRIPTION | HARDWARE DATABASE FILES | EXAMPLES | SEE ALSO | COLOPHON |
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HWDB(7) hwdb HWDB(7)
hwdb - Hardware Database
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.
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.
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:bvr: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
systemd-hwdb(8)
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 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel HWDB(7)
Pages that refer to this page: sd-hwdb(3), sd_hwdb_get(3), machine-info(5), systemd.directives(7), systemd.index(7), systemd-hwdb(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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