Ubuntu Manpage: apmd - Advanced Power Management (APM) daemon

NAME

       apmd - Advanced Power Management (APM) daemon

SYNOPSIS

       apmd [ -TVWciqv ] [ -P program ] [ -T seconds ] [ -c seconds ] [ -p percent ] [ -v level ]
       [ -w percent ]

DESCRIPTION

apmd is an monitoring daemon for the Advanced Power Management (APM) subsystem. The APM
subsystem consists of power-management hardware, firmware usually referred to as the APM
BIOS and a driver in the operating system kernel. The daemon can execute a program
(usually a shell script) when events are reported by the APM subsystem, and will log, via
syslogd(8), certain changes in power status. When the available battery power becomes
very low it can alert the user.

When the APM subsystem notifies the daemon of a pending suspend or standby request, apmd
will run a proxy program, log the event, sync(2) data to the disk and then tell the APM
subsystem to continue its operation.

Preparations for power management events are made mainly by the proxy program specified
using the -P option. The proxy program is invoked with one or two arguments:

start Invoked when the daemon starts.

stop Invoked when the daemon stops.

standby ( system | user )
Invoked when the APM subsystem reports that standby has been initiated. The second
parameter indicates whether firmware ("system") or software ("user") was the
originator of the event.

The "standby" mode conserves power but leaves the machine able to respond almost
immediately to user activity. Most laptops can't stay in standby mode on battery
power for more than a few hours or a day. Normally, nothing special needs to be
done to prepare for "standing by".

suspend ( system | user )
Invoked when the APM subsystem reports that suspension has been initiated. The
second parameter indicates whether firmware ("system") or software ("user") was the
originator of the event.

The "suspend" mode aggressively conserves power. Usually this involves shutting
off power to all devices except the CPU core and memory, which are put into a very
low power mode. Most laptops can stay suspended, using battery power alone, for
several days. ("Hibernation" is a kind of super-suspend, where all that state is
written to disk and the machine uses no power. Hibernation is treated like
suspension by the APM subsystem.)

Before suspending, PCMCIA devices may need to be disabled using cardctl(8), and
some modular device drivers may need to be unloaded if they have not been designed
to support power management.

resume ( suspend | standby | critical )
Invoked when the APM subsystem reports that computer has resumed normal operation.
The second parameter indicates the kind of event from which the system is resuming.
(A "critical" suspend is a suspension that the APM subsystem performs in an
emergency. Some kernels do not pass this event to user space. If apmd receives
the event, it acknowledges the event and exits immediately without logging or
running the proxy program.)

When resuming, PCMCIA devices may need to be re-enabled using cardctl(8), and some
modular drivers may need to be reloaded. Note that in the case of a critical
suspend, the system state may not have been completely saved.

change power
Invoked when the APM subsystem reports a change in power status, such as a switch
from mains to battery power.

change battery
Invoked when the APM subsystem reports that the charge of one or more batteries is
low. A few minutes of battery power may remain.

change capability
Invoked when the APM subsystem reports some change in power management
capabilities. It may have been caused by operation of a setup utility, or by the
installation or removal of devices.

apmd emits various messages, most of which are self-explanatory. Battery status log
entries contain three fields, separated by commas. The first field indicates how full the
battery is as a percentage of its capacity. The second field indicates whether the
battery is charging, not charging, or discharging. When possible, apmd adds in
parentheses its estimate of the rate of charging or discharging. The third field
indicates how much time the battery can or could be used to power the computer. This
information is provided by the APM subsystem. When possible, apmd adds in parentheses its
own estimate of the battery life (if discharging) or of the time required to charge the
battery fully (if charging).

OPTIONS

-P program, --proxy program
Specifies the proxy program to execute when events are received. See above for
information about the arguments supplied to this program.

-T [seconds] , --proxy-timeout [seconds]
Sets a time-out for the proxy. Without this option (or with this option and a
negative argument) apmd waits indefinitely for the proxy to finish. If the proxy
enters an infinite loop or wait then the machine may appear to have crashed. If
this option is given a positive integer argument then apmd will wait only that many
seconds for the proxy to finish, after which it will log a warning, kill the proxy,
and continue processing the event. The default is 30 seconds.

-V, --version
Prints the version of the apmd program.

-W, --wall
In addition to logging low battery status (as determined either by the -w level or
by the firmware) using syslog(2), apmd will, given this option, also use wall(1) to
alert all users. This is most useful if syslogd(8) is not set up to write ALERT
messages to all users. If both methods are used, more warnings will be made during
the critical time period.

-c [seconds] , --check [seconds]
Controls how many seconds to wait for an event. Without this option (or with this
option and a negative argument) apmd waits indefinitely for an event. If this
option is given a positive integer argument then apmd will wait only that many
seconds before checking the battery level and possibly sending out a warning,
calling the proxy or making an entry in the log. The default is 30 seconds.

-i, --ignore-bios-battery-low
Causes apmd to ignore a LOW BATTERY signal sent by the APM subsystem. Some
firmware signals a low battery at the wrong time. Note that LOW BATTERY events may
still be generated by apmd itself based on the warning level.

-p percent, --percentage percent
Controls how often the battery status is logged. A new line is printed each time
the battery content changes by percent_change if logging is enabled. The default
is 5. Use a value greater than 100 to disable periodic logging of the battery
level.

-q, --quiet-bios-battery-low
Causes apmd not to generate a warning when a LOW BATTERY signal is received from
the APM subsystem. The firmware on some machines produces an audible warning when
power is about to be used up, so an extra warning may not be needed.

-v [level] , --verbose [level]
The daemon can generate messages of varying degrees of unimportance. Each message
is assigned one of the priority levels defined for the syslogd(8) subsystem,
ranging from 0 (EMERG, least unimportant) to 7 (DEBUG, most unimportant). This
option sets the threshold level above which messages are suppressed. Without an
argument it increments the threshold by 1, thus making apmd more verbose. The
default is 5 (NOTICE).

-w percent, --warn percent
When the battery is not being charged and the battery content falls below the
specified percent of capacity, and no such event has yet occurred in the current
discharge cycle, apmd will log a warning at the ALERT log level to syslog(2) and
generate a LOW BATTERY event. If the -W or --wall option was given, the daemon
will also use wall(1) to alert all users of impending doom. The default warning
level is 10. Use a negative value to disable this feature.

-h, --help
Causes apmd to print a brief command summary and exit.

BUGS

       This daemon supports all APM events described in the APM BIOS specification  version  1.2;
       however  it  fails  to support some of the advanced features of APM 1.2, such as reporting
       the conditions of multiple batteries.  (Multiple batteries are  currently  treated  as  if
       they were just one large one.)

       Estimates of charge and discharge rates and times can be very inaccurate.

       There is no interaction yet with ACPI support as found in newer PC hardware.

FILES

       /dev/apm_bios
              Device through which apmd communicates with the Linux APM driver.

       /proc/apm
              APM driver status information

       /etc/apmd_proxy
              Proxy program that is run if none is specified.

       /etc/apm/apmd_proxy
              Proxy program that is run if none is specified. (Debian)

AUTHOR

       This  program  was  written  by Rik Faith (faith@cs.unc.edu) and may be freely distributed
       under the terms of the GNU General Public License.  There is ABSOLUTELY  NO  WARRANTY  for
       this program.  The current maintainer is Avery Pennarun (apenwarr@worldvisions.ca).