Manual browser: apmd(8)

APMD(8) System Manager's Manual APMD(8)


apmdAdvanced Power Management monitor daemon


apmd [-adlqsv] [-f devname] [-m sockmode] [-o sockowner:sockgroup] [-S sockname] [-t rate]


The apmd daemon monitors the Advanced Power Management (APM) pseudo-device, acting on signaled events and upon user requests as sent by the apm(8) utility. The apmd daemon is only installed on supported platforms.

The apmd is largely deprecated. Modern systems supporting ACPI should rely on acpi(4), powerd(8), and the envsys(4) framework instead.

For suspend and standby request events delivered by the BIOS, or via apm(8), apmd runs the appropriate configuration program (if one exists), syncs the buffer cache to disk and initiates the requested mode. When resuming after suspend or standby, apmd runs the appropriate configuration utility (if one exists). For power status change events, apmd fetches the current status and reports it via syslog(3) with logging facility LOG_DAEMON.

apmd announces the transition to standby mode with a single high tone on the speaker (using the /dev/speaker device). Suspends are announced with two high tones.

apmd periodically polls the APM driver for the current power state. If the battery charge level changes substantially or the external power status changes, the new status is logged. The polling rate defaults to once per 10 minutes, but this may be altered by using the -t command-line flag.

apmd supports the following options:

Any BIOS-initiated suspend or standby requests are ignored if the system is connected to line current and not running from batteries (user requests are still honored).
Enter debug mode, log to facility LOG_LOCAL1 and stay in the foreground on the controlling terminal.
-f devname
Specify an alternate device file name.
A low-battery event causes a suspend request to occur.
-m sockmode
Use sockmode instead of ‘0660’ for the mode of /var/run/apmdev.
-o sockowner:sockgroup
Use sockowner:sockgroup instead of ‘`0:0'’ for the owner/group of /var/run/apmdev.
Do not announce suspend and standby requests on the speaker.
-S sockname
Specify an alternate socket name (used by apm(8) to communicate with apmd).
The current battery statistics are reported via syslog(3) and exit without monitoring the APM status.
-t rate
Change the polling rate from 600 seconds to rate seconds.
Periodically log the power status via syslog(3).

When a client requests a suspend or stand-by mode, apmd does not wait for positive confirmation that the requested mode has been entered before replying to the client; to do so would mean the client does not get a reply until the system resumes from its sleep state. Rather, apmd replies with the intended state to the client and then places the system in the requested mode after running the configuration script and flushing the buffer cache.

Actions can be configured for the five transitions: suspend, standby, resume, line or battery. The suspend and standby actions are run prior to apmd performing any other actions (such as disk syncs) and entering the new mode. The resume program is run after resuming from a stand-by or suspended state.

The line and battery actions are run after switching power sources to AC (line) or battery, respectively. The appropriate line or battery action is also run upon the startup of apmd based on the current power source.


Contain the host's customized actions. Each file must be an executable binary or shell script suitable for execution by the execve(2) function. If you wish to have the same program or script control all transitions, it may determine which transition is in progress by examining its argv[0] which is set to one of suspend, standby, resume, line or battery. See /usr/share/examples/apm/script for such an example script.

The default UNIX-domain socket used for communication with apm(8). The socket is protected by default to mode 0660, UID 0, GID 0.

The default device used to control the APM kernel driver.


The apmd daemon appeared in NetBSD 1.3.
March 20, 2010 NetBSD 7.0