acpid - Advanced Configuration and Power Interface event daemon
is designed to notify user-space programs of ACPI events.
should be started during the system boot, and will run as a
background process, by default. It will open an events file (
by default) and attempt to read whole lines which
represent ACPI events. If the events file does not exist, acpid
attempt to connect to the Linux kernel via the input layer and netlink. When
an ACPI event is received from one of these sources, acpid
a list of rules, and execute the rules that match the event. acpid
ignore all incoming ACPI events if a lock file exists ( /var/lock/acpid
are defined by simple configuration files. acpid
in a configuration directory ( /etc/acpi/events
by default), and parse
all regular files with names that consist entirely of upper and lower case
letters, digits, underscores, and hyphens (similar to run-parts(8)). Each file
must define two things: an event
and an action
. Any blank lines,
or lines where the first character is a hash ('#') are ignored. Extraneous
lines are flagged as warnings, but are not fatal. Each line has three tokens:
the key, a literal equal sign, and the value. The key can be up to 63
characters, and is case-insensitive (but whitespace matters). The value can be
up to 511 characters, and is case and whitespace sensitive.
The event value is a regular expression (see regcomp(3)), against which events
The action value is a commandline, which will be invoked via /bin/sh
whenever an event matching the rule in question occurs. The commandline may
include shell-special characters, and they will be preserved. The only special
characters in an action value are "%" escaped. The string
"%e" will be replaced by the literal text of the event for which the
action was invoked. This string may contain spaces, so the commandline must
take care to quote the "%e" if it wants a single token. The string
"%%" will be replaced by a literal "%". All other
"%" escapes are reserved, and will cause a rule to not load.
This feature allows multiple rules to be defined for the same event (though no
ordering is guaranteed), as well as one rule to be defined for multiple
events. To force acpid
to reload the rule configuration, send it a
The pseudo-action <drop>
causes the event to be dropped completely
and no further processing undertaken; clients connecting via the UNIX domain
socket (see below) will not be notified of the event. This may be useful on
some machines, such as certain laptops which generate spurious battery events
at frequent intervals. The name of this pseudo-action may be redefined with a
In addition to rule files, acpid
also accepts connections on a UNIX
domain socket ( /var/run/acpid.socket
by default). Any application may
connect to this socket. Once connected, acpid
will send the text of all
ACPI events to the client. The client has the responsibility of filtering for
messages about which it cares. acpid
will not close the client socket
except in the case of a SIGHUP or acpid
For faster startup, this socket can be passed in as stdin so that acpid
need not create the socket. In addition, if a socket is passed in as stdin,
will not daemonize. It will be run in foreground. This behavior
is provided to support systemd(1).
will log all of its activities, as well as the stdout and stderr of
any actions, to syslog.
All the default files and directories can be changed with commandline options.
- -c, --confdir directory
- This option changes the directory in which acpid
looks for rule configuration files. Default is
- -C, --clientmax number
- This option changes the maximum number of non-root socket
connections which can be made to the acpid socket. Default is
- -d, --debug
- This option increases the acpid debug level by one.
If the debug level is non-zero, acpid will run in the foreground,
and will log to stderr, in addition to the regular syslog.
- -e, --eventfile filename
- This option changes the event file from which acpid
reads events. Default is /proc/acpi/event.
- -n, --netlink
- This option forces acpid to use the Linux kernel
input layer and netlink interface for ACPI events.
- -f, --foreground
- This option keeps acpid in the foreground by not
forking at startup.
- -l, --logevents
- This option tells acpid to log information about all
events and actions.
- -L, --lockfile filename
- This option changes the lock file used to stop event
processing. Default is /var/lock/acpid.
- -g, --socketgroup
- This option changes the group ownership of the UNIX domain
socket to which acpid publishes events.
- -m, --socketmode mode
- This option changes the permissions of the UNIX domain
socket to which acpid publishes events. Default is
- -s, --socketfile filename
- This option changes the name of the UNIX domain socket
which acpid opens. Default is /var/run/acpid.socket.
- -S, --nosocket filename
- This option tells acpid not to open a UNIX domain
socket. This overrides the -s option, and negates all other socket
- -p, --pidfile filename
- This option tells acpid to use the specified file as
its pidfile. If the file exists, it will be removed and over-written.
Default is /var/run/acpid.pid.
- -r, --dropaction action
- This option defines the pseudo-action which tells
acpid to abort all processing of an event, including client
notifications. Default is <drop>.
- -t, --tpmutefix
- This option enables special handling of the mute button for
certain ThinkPad models with mute LEDs that get out of sync with the mute
state when the mute button is held down. With this option, the mute button
will generate the following events in sync with the number of presses
(and, by extension, the state of the LED):
button/mute MUTE (key pressed) K
button/mute MUTE (key released) K
- -v, --version
- Print version information and exit.
- -h, --help
- Show help and exit.
This example will shut down your system if you press the power button.
Create a file named /etc/acpi/events/power that contains the following:
Then create a file named /etc/acpi/power.sh that contains the following:
- /sbin/shutdown -h now "Power button pressed"
Now, when acpid
is running, a press of the power button will cause the
rule in /etc/acpi/events/power to trigger the script in /etc/acpi/power.sh.
The script will then shut down the system.
is a simple program that runs scripts in response to ACPI events
from the kernel. When there's trouble, the problem is rarely with acpid
itself. The following are some suggestions for finding the most common sources
of ACPI-related problems.
When troubleshooting acpid
, it is important to be aware that other parts
of a system might be handling ACPI events. systemd
(1) is capable of
handling the power switch and various other events that are commonly handled
. See the description of HandlePowerKey in
(5) for more. Some window managers also take over
's normal handling of the power button and other events.
kacpimon(8) can be used to verify that the expected ACPI events are coming in.
See the man page for kacpimon(8) for the proper procedure. If the events
aren't coming in, you've probably got a kernel driver issue.
If the expected events are coming in, then you'll need to check and see if your
window manager is responsible for handling these events. Some are, some
aren't. (E.g. in Ubuntu 14.04 (Unity/GNOME), there are settings for the laptop
lid in the System Settings > Power > "When the lid is closed"
fields.) If your window manager is responsible for handling the problematic
event, and you've got it configured properly, then you may have a window
Lastly, take a look in /etc/acpi/events
(see above). Is there a
configuration file in there for the event in question (e.g.
/etc/acpi/events/lidbtn for laptop lid open/close events)? Is it properly
connected to a script (e.g. /etc/acpi/lid.sh)? Is that script working? It's
not unusual for an acpid
script to check and see if there is a window
manager running, then do nothing if there is. This means it is up to the
window manager to handle this event.
should work on any linux kernel released since 2003.
There are no known bugs. To file bug reports, see PROJECT WEBSITE
regcomp(3), sh(1), socket(2), connect(2), init(1), systemd(1), acpi_listen(8),
Ted Felix <firstname.lastname@example.org>
Tim Hockin <email@example.com>