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 /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 /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 /lib, pointing to /dev/null, disables the hwdb file
entirely. hwdb files must have the extension .hwdb; other extensions
The 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 database
lookup string against. Multiple match lines are specified in additional
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.
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
/lib/udev/hwdb.bin if you want ship the compiled database in an
immutable image. During runtime, only the binary database is used.
systemd 229 HWDB(7)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2019
All Rights Reserved.