man/hwdb.7

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   2 .TH "HWDB" "7" "" "systemd 219" "hwdb"
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  22 .SH "NAME"
  23 hwdb \- Hardware Database
  24 .SH "DESCRIPTION"
  25 .PP
  26 The hardware database is a key\-value store for associating modalias\-like keys to udev\-properties\-like values\&. It is used primarily by udev to add the relevant properties to matching devices, but it can also be queried directly\&.
  27 .SH "HARDWARE DATABASE FILES"
  28 .PP
  29 The hwdb files are read from the files located in the system hwdb directory
  30 /usr/lib/udev/hwdb\&.d, the volatile runtime directory
  31 /run/udev/hwdb\&.d
  32 and the local administration directory
  33 /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
  34 /etc
  35 have the highest priority, files in
  36 /run
  37 take precedence over files with the same name in
  38 /usr/lib\&. This can be used to override a system\-supplied hwdb file with a local file if needed; a symlink in
  39 /etc
  40 with the same name as a hwdb file in
  41 /usr/lib, pointing to
  42 /dev/null, disables the hwdb file entirely\&. hwdb files must have the extension
  43 \&.hwdb; other extensions are ignored\&.
  44 .PP
  45 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 string, 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 indivdually, they are combined by OR\&. Every match line must start at the first character of the line\&.
  46 .PP
  47 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
  48 "="\&. An empty line signifies the end of a record\&. Lines beginning with
  49 "#"
  50 are ignored\&.
  51 .PP
  52 The content of all hwdb files is read by
  53 \fBsystemd-hwdb\fR(8)
  54 and compiled to a binary database located at
  55 /etc/udev/hwdb\&.bin, or alternatively
  56 /usr/lib/udev/hwdb\&.bin
  57 if you want ship the compiled database in an immutable image\&. During runtime only the binary database is used\&.
  58 .SH "SEE ALSO"
  59 .PP
  60 \fBsystemd-hwdb\fR(8)