.\" apmd.8 -- 
.\" Created: Wed Jan 10 15:07:25 1996 by faith@acm.org
.\" Revised: Fri Dec 26 20:34:52 1997 by faith@acm.org
.\" Revised: Wed Jun  2 18:47:02 1999 by db@post.harvard.edu
.\" Copyright 1996, 1997 Rickard E. Faith (faith@acm.org)
.\" Copyright 1999 David Brownell (db@post.harvard.edu)
.\" 
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.\" preserved on all copies.
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.\" Permission is granted to copy and distribute modified versions of this
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.\" entire resulting derived work is distributed under the terms of a
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.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" 
.TH APMD 8 "10 Jun 1999" "" "Linux Programmer's Manual"
.SH NAME
apmd \- Advanced Power Management (APM) daemon
.SH SYNOPSIS
.BI "apmd"
.BI "[ \-c " check_seconds " ]
.BI "[ \-P " proxy_cmd " ]"
.BI "[ \-p " percent_to_log " ]"
.BI "[ \-qVvW ]"
.BI "[ \-w " warn_percent " ]
.BI "[ \-? ]"
.I "[deprecated options]"
.SH DESCRIPTION
.B apmd
is an APM monitoring daemon, and works in conjunction with the
APM BIOS driver in the OS kernel.  It can execute a command (normally a shell
script) when certain events are reported by the driver, and will log, via
.BR syslogd (8),
certain changes in system power status.  When the available battery power becomes
very low, it can alert all users on the system using several methods.
.PP
When the kernel APM driver notifies the daemon of
a pending suspend or standby request,
.B apmd
will invoke the approprate command,
log the event, 
.BR sync (2)
data to the disk,
sleep briefly to help ensure all the data actually gets to the disk,
and then tell the APM driver to continue its operation.
However, for "critical" suspends (indicating an emergency shutdown)
only the last step (telling the driver to continue) is performed.
.PP
Most uses of this daemon will use the
.I proxy
command to support power conservation activities.  This command is
searched for by default in
.I /etc/apmd_proxy
and is invoked with one or two arguments:
.TP
.B start
Invoked when the daemon starts.  Normally sets system-wide power policy, such as
IDE hard drive standby times, to account for whether battery power is in use.
.TP
.B stop
Invoked when the daemon stops.  Normally undoes any policy settings done when the
daemon started.
.TP
.B suspend "[ system | user ]"
.\".B suspend "[ system | user | critical ]"
Invoked when the APM driver reports that system suspension has been initiated.
The second parameter indicates whether the BIOS or a user action (such as closing
a laptop) initiated suspension.
.ig
A "critical" suspend is initiated by the BIOS when an emergency shutdown needs
to happen.  Applications and device drivers are not be notified since there
isn't enough time to safely do anything about the shutdown.
..
.sp
The BIOS "suspend" mode aggressively conserves power, and normally involves
shutting off power to all devices except the CPU core and memory, which is kept
in 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 even less power bcause it
can turn off that CPU core, using no battery power at all.  At this writing,
Linux does not support hibernation.)
PCMCIA devices should be manually suspended using
.BR cardctl (8),
and some modular drivers may need to be unloaded.
.TP
.B standby "[ system | user ]"
Invoked when the APM driver reports that system standby has been initiated.
The second parameter indicates whether the BIOS or a user action (such as
invoking
.IR "apm -s" )
caused this.
.sp
The BIOS "standby" mode slightly conserves power, and leaves the
machine able to respond almost immediately to user activity.
Most laptops can't stay in standby mode for even a day, if they must
rely on battery power.  Normally, nothing needs to be done beyond
what the BIOS itself will do.
.TP
.B resume "[ suspend | standby | critical ]"
Invoked when the APM driver reports that system has resumed normal operation.
The second parameter indicates what sort of mode it was in before, either
the "suspend" mode (possibly a "critical" suspend) or else "standby" mode.
.sp
The system clock must be updated to match the hardware clock; this will
normally have been handled by the kernel's APM driver.
PCMCIA devices may need to be manually resumed from standby using
.BR cardctl (8),
and some modular drivers may need to be reloaded or otherwise reinitialized.
In the case of a critical suspend, system state may not have been completely
saved due to an emergency shutdown; applications and and drivers may be in
a confused state.
.TP
.B change power
This presents a subset of the APM driver "power change" events, specifically
those where AC power was added or removed.
This will often modify the system wide power policy; for example, so that IDE
hard drives aggressively enter standby mode when only battery power is available.
.ig
.TP
.B change time
The system clock must be updated to match the hardware clock; this will
normally have been handled by the kernel's APM driver.
..
.TP
.B change battery
The APM driver has reported that the BIOS thinks the strength of one (or more)
batteries is "low"; at least ten minutes of should power remain.
.TP
.B change capability
Some change in the power management capabilities of the system was reported.
It may have been caused by operation of some setup utility, or by the arrival
or removal of some devices.
.PP
This daemon issues a number of different log messages, most of which should
be self explanatory.  The messages emitted for battery status need some
explanation, however. 
The information logged contains 4 fields after a "Battery" or "Charge" label:
.HP
1) Rate of discharge (percent/minute).  Negative rates indicate charging.
.HP
2) Time since total charge or total discharge (hh:mm:ss).  This value is
only useful if it reflects the time since a 100% or 0% state has been
reached.  Otherwise, this time is in parentheses, and reflects the time
since the last "important"
.B apmd
status change such as starting the daemon, changing from AC power to battery
power, and so on.
.HP
3) Estimate of time left until total discharge (or total charge), assuming
use similar to that since the last resume ( or since AC was connected).
This time is calculated by
.B apmd
itself.
.HP
4) Parenthetically, the percent and length of remaining battery life, as
estimated by the APM BIOS (which is often a conservative estimate from an
intelligent battery itself).  This particular information is provided with
most messages from this daemon.
.PP
This daemon supports APM BIOS 1.2 events, though it does not support some
of the advanced features such as multiple batteries.  Also,
there is no interaction yet with ACPI support as found in newer PC hardware.
.SH OPTIONS
.TP
.BR "\-c " seconds, " \--check " seconds
Controls how many seconds to block on the \fI/dev/apm_bios\fR device.  Normally
the daemon blocks until the APM driver reports an event; this number may be
changed to cause battery charge or discharge rates to be checked more often.
.TP
.BR "\-P " proxy_cmd, " \-\-apmd_proxy " proxy_cmd
Identifies the command to invoke when certain APM driver events are reported.
See above for information about the arguments to this script.
.TP
.BR "\-p " percent_change, " \--percentage " percent_change
Every time the percentage of available power changes (discharge or recharge) by
.IR percent_change ,
log information.  The default is 5.  Use values greater than 100 to disable
this feature.
.TP
.B \-V, \-\-version
Print the daemon's version and exit.
.TP
.B \-v, \-\-verbose
Enables verbose mode, where each event reported by the APM driver is logged.
.TP
.B \-W, \-\-wall
In addition to logging low battery status (as determined either by
the \fB-w\fR level or by the APM BIOS) using
.BR syslog (2),
also use
.BR wall (1)
to alert all users.  This is most useful if
.BR 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.
.TP
.BR "\-w " warn_percent, " \--warn " warn_percent
When the battery is not being charged and the percentage of available power
drops below
.IR warn_percent ,
log a warning at ALERT level to
.BR syslog (2).
If the
.B \-W
or
.B \-\-wall
flag was given, the daemon will also use
.BR wall (1)
to alert all users of impending doom.  Give the warning each time the
percentage changes.  The default is 10.  Use negative values to disable
this feature.
.TP
.B \-q, \-\-quiet
Disables the warnings identified by the 
.B -W
and
.B -w
options.  (The APM BIOS on many machines will provide an audible warning
when power is about to be used up, so those extra warnings may not be needed.)
.TP
.B \-?, \-\-help
Prints a usage message and exits.
.PP
New software should only use the
.I proxy
script, rather than the following now-deprecated options (most of which
have never appeared in a production release).
If they are provided, they take precedence over any proxy command
invocation for each event.
.TP
.BR "\-a " ac_online_cmd, " \-\-ac_online " ac_online_cmd
Provides a command to be run when AC power becomes available, though not
when the daemon first starts.
.TP
.BR "\-b " ac_offline_cmd, " \-\-ac_offline " ac_offline_cmd
Provides a command to be run when the machine is operating on
battery power, though not when the daemon first starts.
.TP
.BR "\-l " low_battery_cmd, " \-\-low_battery " low_battery_cmd
Provides a command to be run when the APM BIOS judges that
battery power is "low".
.TP
.BR "\-s " pre_suspend_cmd, " \-\-pre_suspend " pre_suspend_cmd
Provides a command to be run before suspending through the driver. 
.TP
.BR "\-r " post_resume_cmd, " \-\-post_resume " post_resume_cmd
Provides a command to be run after resuming through the driver. 
.TP
.B \-u, \-\-utc
(This option is now completely ignored.)
The BIOS clock is set to UTC (GMT), so the daemon should pass the -u option to the
.I clock
or
.I hwclock
program when coming out of suspend or resume mode, or when responding
to the BIOS update time event.
.SH BUGS
The first status report printed after a power change may be
inaccurate because the power change occured at a fractional percentage that
was rounded to a full percentage.  For example, say you are discharging the
machine and have 50.9% power, which is reported as 50%.  When you start to
charge the machine, it will only have 0.1% left before the percentage flips
to 51%, and the charge rate will be dramatically over-estimated.
.PP
There needs to be a more general hook to let other applications participate
in system power management decisions and policies.
.PP
Multiple batteries are currently treated as if they were just one large one.
.SH FILES
.I /dev/apm_bios
.br
.I /proc/apm
.br
.I /etc/apmd/apmd_proxy
.SH 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).
.SH "SEE ALSO"
.BR apm "(1), " xapm "(1), " cardctl "(8), " hdparm "(8), " syslogd "(8)"