acpid - Advanced Configuration and Power Interface event daemon
acpid is designed to notify user-space programs of ACPI events.
acpid should be started during the system boot, and will run as a
background process, by default. It will open an events file
(/proc/acpi/event by default) and attempt to read whole lines which
represent ACPI events. If the events file does not exist, acpid will
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 will examine a
list of rules, and execute the rules that match the event. acpid will
ignore all incoming ACPI events if a lock file exists (/var/lock/acpid by
Rules are defined by simple configuration files. acpid
will look 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
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 are matched.
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
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 SIGHUP.
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 exiting.
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 /etc/acpi/events.
-C, --clientmax number
This option changes the maximum number of non-root socket connections which
can be made to the acpid socket. Default is 256.
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.
This option forces acpid to use the Linux kernel input layer and netlink interface for ACPI events.
This option keeps acpid in the foreground by not forking at startup.
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 groupname
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 0666.
-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 options.
-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.
Print version information and exit.
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.
acpid should work on any linux kernel released since 2003.