acpid man page on ElementaryOS

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acpid(8)							      acpid(8)

       acpid - Advanced Configuration and Power Interface event daemon

       acpid [options]

       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 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 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  command‐
       line  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 comman‐
       dline 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 SIGHUP.

       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 spu‐
       rious battery events at frequent intervals. The name  of	 this  pseudo-
       action may be redefined with a commandline option.

       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.

       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, acpid will not daemonize.	 It will be run in  foreground.	  This
       behavior is provided to support systemd(1).

       acpid  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

       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	by  acpid.   See  the	description   of   HandlePowerKey   in
       logind.conf(5)  for  more.  Some window managers also take over acpid's
       normal handling of the power button and other events.

       -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.

       -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

       -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 pro‐
		   cessing.  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

       -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/

       -r, --dropaction action
		   This	 option defines the pseudo-action which tells acpid to
		   abort all processing of an event, including client  notifi‐
		   cations.  Default is <drop>.

       -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:

	      action=/etc/acpi/ "%e"

       Then  create  a file named /etc/acpi/ that contains the follow‐

	      /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/  The script will then shut down the system.

       acpid 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), kacpimon(8)


       Ted Felix (ted -at- tedfelix -dot- com)
       Tim Hockin <>
       Andrew Henroid


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