HWDB - Online Linux Manual PageSection : 7
Updated :
Source : systemd 253
Note : hwdb
NAMEhwdb − Hardware Database
DESCRIPTIONThe 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 FILESThe 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​. Match patterns consist of literal characters, and shell−style wildcards: •  Asterisk "*" matches any number of characters •  Question mark "?" matches a single character •  Character list "[chars]" matches one of the characters chars listed between "[" and "]"​. A range may be specified as with a dash as "[first−last]"​. The match may be inverted with a caret "[^​...]"​. 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​.
EXAMPLESExample ​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 # The rule above could be also be written in a form that # matches Tb, tb, TB, tB: mouse:*:name:*[tT]rack[bB]all*:* 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=14Example ​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 # Match vendor name "Acer" and any product name starting with "X123" evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer:pnX123*:* KEYBOARD_KEY_a2=wlan # /etc/udev/hwdb​.d/70−keyboard​.hwdb # disable wlan key on all at keyboards evdev:atkbd:* KEYBOARD_KEY_a2=reserved PROPERTY_WITH_SPACES=some stringIf the hwdb consists of those two files, a keyboard with the lookup string "evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pnX123" will match all three records, and end up with the following properties: KEYBOARD_KEY_a1=help KEYBOARD_KEY_a2=reserved KEYBOARD_KEY_a3=battery PROPERTY_WITH_SPACES=some string
SEE ALSOsystemd-hwdb(8) 0
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