hwdb
TLDR
Update hardware database
$ sudo systemd-hwdb update
Query device properties$ systemd-hwdb query [modalias]
Show hardware database path$ systemd-hwdb --help
SYNOPSIS
systemd-hwdb [options] command
DESCRIPTION
hwdb (Hardware Database) is a systemd component that maps hardware properties to udev device attributes. It matches hardware by modalias strings and sets properties like device names, permissions, and driver hints.
The database is compiled from text files in /usr/lib/udev/hwdb.d/ and /etc/udev/hwdb.d/ into a binary format for fast matching.
PARAMETERS
update
Compile hwdb files to binary.query modalias
Query properties for modalias.--path path
Custom hwdb path.--root root
Root directory.--strict
Strict parsing mode.--usr
Use /usr directory.
HWDB FILE FORMAT
$ # /etc/udev/hwdb.d/70-custom.hwdb
# Match USB keyboard
usb:v04D9p1702*
KEYBOARD_KEY_70039=leftctrl
KEYBOARD_KEY_3a=capslock
# Match by PCI ID
pci:v00001234d00005678*
ID_VENDOR=Custom Vendor
# Match USB keyboard
usb:v04D9p1702*
KEYBOARD_KEY_70039=leftctrl
KEYBOARD_KEY_3a=capslock
# Match by PCI ID
pci:v00001234d00005678*
ID_VENDOR=Custom Vendor
USAGE
$ # Update after editing hwdb files
sudo systemd-hwdb update
sudo udevadm trigger
# Find modalias for device
udevadm info /dev/input/event0 | grep MODALIAS
sudo systemd-hwdb update
sudo udevadm trigger
# Find modalias for device
udevadm info /dev/input/event0 | grep MODALIAS
CAVEATS
Changes require hwdb update and udevadm trigger. Modalias format varies by bus type. Incorrect entries may cause device issues.
SEE ALSO
udevadm(8), udev(7), systemd-udevd(8)
