acpid

acpid [options]

-c
    Specify the configuration file. The default is /etc/acpi/acpid.conf.

-d
    Run in debug mode. This mode prints more verbose output to the console.

-e
    Specify the event socket. The default is /var/run/acpid.socket.

-f
    Run in the foreground. This prevents acpid from detaching from the terminal.

-l
    Specify the address to listen on. The default is localhost

-m
    Sets the umask for files created by acpid (default 022).

-p
    Specify the pid file. The default is /var/run/acpid.pid.

-s
    Suppress syslog output (useful in conjunction with -d).

-S
    Run in single process mode. Normally, the daemon forks a new process to handle each request.

-g
    Use systemd-run to spawn event handlers.

-h
    Display help and exit.

The acpid daemon is a flexible and extensible daemon for executing commands when ACPI events occur.
It listens for ACPI events from the kernel and executes scripts based on the event type. This allows the system to react to events such as power button presses, battery status changes, lid closures, and thermal zone changes. The configuration of acpid is typically done through a configuration file which maps events to specific shell commands or scripts.
acpid plays a crucial role in power management and system automation, enabling laptops and desktops to intelligently respond to changes in their environment. The scripts are often used for hibernating or shutting down the system, adjusting screen brightness, and other power-saving measures.
Its flexibility allows administrators to customize the system's response to a wide range of ACPI events, making it a fundamental component for modern Linux systems.

acpid relies on the kernel's ACPI support. If ACPI is not properly configured in the kernel or the BIOS, acpid may not function correctly.
Misconfigured scripts can lead to unexpected system behavior, so testing them carefully is advised.

The configuration file (typically /etc/acpi/acpid.conf) defines how acpid responds to different events. It uses a simple syntax to map event names to shell commands or scripts.
Configuration files allows you to handle events like lid switch, power button press and battery events.

acpid was created to replace the older apmd (Advanced Power Management Daemon).
The development of acpid was driven by the need for a more flexible and extensible event handling system compared to apmd.
The usage increased with the adoption of ACPI standards, becoming a key part of power management on Linux systems. It continues to be maintained and updated to support new ACPI features and hardware.

shutdown(8), systemctl(1), pm-utils(8)