/etc/acpi/events/thinkpad-volume-down is in acpi-support 0.142-6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # Volume Down
event=ibm/hotkey HKEY 00000080 00001016
action=/etc/acpi/voldownbtn.sh
|