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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 default).

       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.  Extra-
       neous 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 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

       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  addi-
       tion,  if a socket is passed in as stdin, acpid will not daemonize.  It will be run in foreground.  This behav-
       ior 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 options.

       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

       -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 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 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

       -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/

       -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 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  trig-
       ger 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 below.

       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