acpid 1.0.10-5ubuntu2.2 (amd64 binary) in ubuntu lucid

 Modern computers support the Advanced Configuration and Power Interface (ACPI)
 to allow intelligent power management on your system and to query battery and
 configuration status.
 .
 ACPID is a completely flexible, totally extensible daemon for delivering
 ACPI events. It listens on netlink interface (or on the deprecated file
 /proc/acpi/event), and when an event occurs, executes programs to handle the
 event. The programs it executes are configured through a set of configuration
 files, which can be dropped into place by packages or by the admin.