# dpkg -l|grep acpi
ii  acpi                             0.09-1                               displays information on ACPI devices
ii  acpi-support                     0.90                                 a collection of useful events for acpi
ii  acpid                            1.0.4-5ubuntu4                       Utilities for using ACPI power management
ii  acpitool                         0.4.4-1                              a small, convenient command-line ACPI client

# ps -ax|grep acpi
Warning: bad ps syntax, perhaps a bogus '-'? See http://procps.sf.net/faq.html
    9 ?        S<     0:00 [kacpid]
   10 ?        S<     0:00 [kacpi_notify]
 3653 ?        Ss     0:00 /usr/sbin/acpid -c /etc/acpi/events -s /var/run/acpid.socket
 3944 ?        S      0:00 /usr/lib/hal/hald-addon-acpi
 5413 pts/1    S+     0:00 grep acpi