acpid

Related articles
ACPI modules
DSDT
acpid2
is a flexible and extensible daemon for delivering
ACPI events
. When an event occurs, it executes programs to handle the event. These events are triggered by certain actions, such as:
Pressing special keys, including the Power/Sleep/Suspend button
Closing a notebook lid
(Un)Plugging an AC power adapter from a notebook
(Un)Plugging phone jack etc.
Note
Desktop environments
, such as
GNOME
,
systemd
login manager, and some
extra key handling
daemons may implement their own event handling schemes, independent of acpid. Running more than one system at the same time may lead to unexpected behaviour, such as suspending two times in a row after one sleep button press. You should be aware of this and only activate desirable handlers.
Installation
Install
the
acpid
package. Then
start/enable
acpid.service
.
Configuration
acpid
comes with a number of predefined actions for triggered events, such as what should happen when you press the Power button on your machine. By default, these actions are defined in
/etc/acpi/handler.sh
, which is executed after any ACPI events are detected (as determined by
/etc/acpi/events/anything
).
Determine the event
Unfortunately, not every computer labels ACPI events in the same way.  For example, the Sleep button may be identified on one machine as
SLPB
and on another as
SBTN
.
To determine how your buttons or
Fn
shortcuts are recognized, run the following command:
# journalctl -f
Now press the Power button and/or Sleep button (e.g.
Fn+Esc
) on your machine. The result should look something this:
logger: ACPI action undefined: PBTN
logger: ACPI action undefined: SBTN
If that does not work, run:
# acpi_listen
or with
openbsd-netcat
:
$ netcat -U /var/run/acpid.socket
Then press the power button and you will see something like this:
button/power PBTN 00000000 00000b31
The output of
acpi_listen
is sent to
/etc/acpi/handler.sh
as $1, $2 , $3 & $4 parameters.
Example:
$1 button/power
$2 PBTN
$3 00000000
$4 00000b31
Define event action
The following is a brief example of one such action. In this case, when the Sleep button is pressed, acpid runs the command
echo -n mem >/sys/power/state
which
should
place the computer into a sleep (suspend) state:
button/sleep)
    case "$2" in
        SLPB) echo -n mem >/sys/power/state ;;
        *)    logger "ACPI action undefined: $2" ;;
    esac
    ;;
The event may be different on different machines. For example if Sleep button is actually recognized as
SBTN
, rather than the
SLPB
label specified in the default
/etc/acpi/handler.sh
. In order for Sleep function to work properly on this machine, we would need to replace
SLPB)
with
SBTN)
.
Using this information as a base, you can easily customize the
/etc/acpi/handler.sh
file to execute a variety of commands depending on which event is triggered.  See the
#Tips and tricks
section below for other commonly used commands.
Note
Events such as
button/power
,
button/lid
,
button/suspend
and
button/hibernate
are handled by
systemd-logind.service(8)
by default, see
Power management#ACPI events
. If handling these events with
acpid
, the handling of these events by logind should either be disabled first, or inhibited.
Alternative configuration
By default, all ACPI events are passed through the
/etc/acpi/handler.sh
script. This is due to the ruleset outlined in
/etc/acpi/events/anything
:
# Pass all events to our one handler script
event=.*
action=/etc/acpi/handler.sh %e
While this works just fine as it is, some users may prefer to define event rules and actions in their own self-contained scripts. The following is an example of how to use an individual event file and corresponding action script:
As root, create the following files:
/etc/acpi/events/sleep-button
event=button/sleep.*
action=/etc/acpi/actions/sleep-button.sh %e
/etc/acpi/actions/sleep-button.sh
#!/bin/sh
case "$3" in
    SLPB) echo -n mem >/sys/power/state ;;
    *)    logger "ACPI action undefined: $3" ;;
esac
Make the script
executable
, and
reload
the
acpid.service
to get acpid to recognize the changes to these files.
Using this method, it is easy to create any number of individual event/action scripts.
Tips and tricks
Note
Some of the actions described here, such as Wi-Fi toggle and backlight control, may already be directly managed by a driver; if this is the case, consult the documentation of the corresponding kernel modules.
Example events
The following are examples of events that can be used in the
/etc/acpi/handler.sh
script. These examples should be modified so that they apply to your specific environment e.g. changing the event variable names interpreted by
acpi_listen
.
To set the laptop screen brightness when plugged in power or not (the numbers might need to be adjusted, see
/sys/class/backlight/acpi_video0/max_brightness
):
ac_adapter)
    case "$2" in
        AC*|AD*)
            case "$4" in
                00000000)
                    echo -n 50 > /sys/class/backlight/acpi_video0/brightness
                    ;;
                00000001)
                    echo -n 100 > /sys/class/backlight/acpi_video0/brightness
                    ;;
            esac
Enabling volume control
Find out the acpi identity of the volume buttons (see above) and substitute it for the acpi events in the files below.
/etc/acpi/events/vol-d
event=button/volumedown
action=amixer set Master 5-
/etc/acpi/events/vol-m
event=button/mute
action=amixer set Master toggle
/etc/acpi/events/vol-u
event=button/volumeup
action=amixer set Master 5+
Note
These commands may not work as expected with PulseAudio.
[1]
For full functionality, run commands as the current user while specifying the
XDG_RUNTIME_DIR
environment variable
, for example with:
# sudo -u
user
XDG_RUNTIME_DIR=/run/user/
user_id
pactl
Tip
Disable or bind the volume buttons in Xorg to prevent conflicts with other applications. See
Xmodmap
for details.
See also
[2]
.
Enabling backlight control
Similar to volume control, acpid enables control of your screen's backlight; to achieve this, write a handler, like this:
/etc/acpi/handlers/bl
#!/bin/sh
bl_dev=/sys/class/backlight/acpi_video0
step=1

case $1 in
  -) echo $(($(< $bl_dev/brightness) - $step)) >$bl_dev/brightness;;
  +) echo $(($(< $bl_dev/brightness) + $step)) >$bl_dev/brightness;;
esac
The event in acpi_listen should be something like:
video/brightnessdown BRTDN 00000087 00000000
video/brightnessup BRTUP 00000086 00000000
Connect them to ACPI events:
/etc/acpi/events/bl_d
event=video/brightnessdown.*
action=/etc/acpi/handlers/bl -
/etc/acpi/events/bl_u
event=video/brightnessup.*
action=/etc/acpi/handlers/bl +
Enabling Wi-Fi toggle
You can also create a simple wireless-power switch by pressing the WLAN button. Here's an example:
/etc/acpi/events/wlan
event=button/wlan
action=/etc/acpi/handlers/wlan
and its handler:
/etc/acpi/handlers/wlan
#!/bin/sh
rf=/sys/class/rfkill/rfkill0

case $(< $rf/state) in
  0) echo 1 >$rf/state;;
  1) echo 0 >$rf/state;;
esac
Disabling ordinary key events
Since
b336c96
acpid generates events for some ordinary key presses, such as arrow keys. This results in event/handler spam, visible in system logs or
top
. Events for these buttons can be dropped in the configuration file:
/etc/acpi/events/buttons
event=button/(up|down|left|right|kpenter)
action=<drop>
Getting user name of the current display
To run commands depending on
Xorg
, defining the X display as well as the MIT magic cookie file (via XAUTHORITY) is required. The latter is a security credential providing read and write access to the X server, display, and any input devices (see
xauth(1)
).
See
[3]
for an example function when using
xinitrc
.
Note
If the LCD backlight is not turned off when the lid is closed, you may do so manually by running
getXuser xset dpms force off
and
getXuser xset dpms force on
respectively on lid close and lid open events. Should the display be blanked, but the backlight left on, instead use
vbetool
with
vbetool dpms off
and
vbetool dpms on
. See also
XScreenSaver#Configuration
.
When using
who
or
w
, make sure
/run/utmp
is created at boot-time. See
utmp(5)
for details.
Connect to acpid socket
In addition to rule files, acpid accepts connections on a UNIX domain socket, by default
/var/run/acpid.socket
. User applications may connect to this socket.
#!/bin/sh

acpi_listen | while read -r event; do
handler.sh
"$event"
done
Where
handler.sh
can be a script similar to
/etc/acpi/handler.sh
.
Disable keyboard and touchpad while laptop lid is closed under Wayland
This example uses
inhibited
property of input device drivers as a replacement for xinput which does not work under Wayland.
button/lid)
		if echo "$3" | grep -iq "open"; then
			echo 'LID opened'
			disabled=0
		fi
		if echo "$3" | grep -iq "close"; then
			echo 'LID closed'
			disabled=1
		fi
		find /sys/devices/platform/i8042/serio* -prune -type d | while IFS= read -r serionumber; do
			find $serionumber/input/* -prune -type d | while IFS= read -r inputdevicepath; do
				if grep -q -i -e "keyboard" -e "touchpad" $inputdevicepath/name; then
					logger "found $(cat $inputdevicepath/name) and set to $disabled"
					echo $disabled > $inputdevicepath/inhibited
				fi
			done
		done
	;;
See also
acpid homepage
Gentoo:ACPI#Configuration