|
NAME | DESCRIPTION | HARDWARE DATABASE FILES | EXAMPLES | SEE ALSO | COLOPHON |
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.
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
# 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
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
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you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
systemd 234 HWDB(7)
Pages that refer to this page: systemd.directives(7), systemd.index(7), systemd-hwdb(8)