hwdb

systemd component that maps hardware properties to udev device attributes

TLDR

Update hardware database

$ sudo systemd-hwdb update

Query device properties

$ systemd-hwdb query [modalias]

Show hardware database path

$ systemd-hwdb --help

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

USAGE

$ # Update after editing hwdb files
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.