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HWDB(7)                              hwdb                              HWDB(7)
NAME
       hwdb - Hardware Database
DESCRIPTION
       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
       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
       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
       systemd-hwdb(8)
systemd 239                                                            HWDB(7)