acpid is a daemon that monitors Advanced Configuration and Power Interface (ACPI) events and executes scripts to respond to them. These events are typically prompted by the user interacting with the hardware, such as closing a laptop lid or pressing the power button.

acpid executes actions based on rules you establish. Certain rules are predefined on installation but can be altered. These rules are set in configuration files created in /etc/acpi/events.

Each file must define an event and an action on separate lines for each rule. The event= line identifies the hardware interaction to be configured. The action= line specifies a shell script containing the configuration, which you must create (typically in /etc/acpi/actions). Multiple rules can be set for each event, or one rule for multiple events.

acpid ships with one shell script at /etc/acpi/actions/power.sh and two configuration files in /etc/acpi/events: powerconf and videoconf. powerconf is structured as follows:

# ACPID config to power down machine if powerbutton is pressed, but only if 
# no gnome-power-manager is running
	      
event=button/power.*
action=/etc/acpi/actions/power.sh

acpid is installed by default in some, but not all Fedora installations.