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

# NAME

`apmd` — Advanced Power Management daemon

# SYNOPSIS

`apmd` | [`-AadHLs`] [`-f` devname] [`-S` sockname] [`-t` seconds] [`-w` percent] [`-Z` percent] [`-z` percent]

# DESCRIPTION

`apmd` monitors the advanced power management device, apm(4), acting on signaled events and upon user requests as sent by the apm(8) program.

On OpenBSD, power management is handled by the kernel, and the default policy can be set using the hw.perfpolicy sysctl(2). If `apmd` is not running, apm(8) is still able to query the apm(4) driver for a limited amount of information, but `apmd` provides more advanced functionality, such as the ability to switch performance modes.

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 state. When resuming after suspend or standby, `apmd` runs the appropriate configuration program (if one exists).

When the power status changes (external power is connected or disconnected), `apmd` fetches the current status and reports it via syslog(3) with logging facility `LOG_DAEMON`.

`apmd` can change the system performance policy at startup when called with the `-A`, `-H` or `-L` options, and during runtime when requested by apm(8). The default performance policy is "high" when connected to line current, and "auto" when running on battery.

The options are as follows:

`-A`
  Start `apmd` in automatic performance adjustment mode.
`-a`
  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).
`-d`
  `apmd` enters debug mode, staying in the foreground. Logging output is printed to stderr.
`-f` devname
  Specify an alternate device file name, devname.
`-H`
  Start `apmd` in manual performance adjustment mode, initialising hw.setperf to 100.
`-L`
  Start `apmd` in manual performance adjustment mode, initialising hw.setperf to 0.
`-S` sockname
  Specify an alternate socket name, sockname. The socket is protected to mode 0660, UID 0, GID 0; this protects access to suspend requests to authorized users only.
`-s`
  Current battery statistics are reported via syslog(3) and `apmd` exits without monitoring the APM status.
`-t` seconds
  `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 may be specified using the `-t` command-line flag.
`-w` percent
  Log warning and enable “warnlow” actions if no AC is connected and the estimated battery life is equal or below percent.
`-Z` percent
  Automatically hibernate the system if no AC is connected and the estimated battery life is equal or below percent.
`-z` percent
  Automatically suspend the system if no AC is connected and the estimated battery life is equal or below percent.

  If both `-Z` and `-z` are specified, the last one will supersede the other. After a resume, the effect of those options is inhibited for 60 seconds.

When a client requests a suspend or stand-by state, `apmd` does not wait for positive confirmation that the requested state 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 state after running the configuration script and flushing the buffer cache.

Actions can be configured for the following transitions: hibernate, powerdown, powerup, resume, standby, suspend, and warnlow. The warnlow action is run if `-w` is used. The suspend, hibernate and standby actions are run prior to `apmd` performing any other actions (such as disk syncs) and entering the new state. The resume program is run after resuming from a stand-by or suspended state. The powerup and powerdown programs are run after the power status (AC connected or not) changes, as well as after a resume (if the power status changed in the mean time).

# FILES

/dev/apmctl
  Default device used to control apm(4).

/etc/apm/hibernate
/etc/apm/powerdown
/etc/apm/powerup
/etc/apm/resume
/etc/apm/standby
/etc/apm/suspend
/etc/apm/warnlow
  Action hook files which, if present, must be executable. Each file must be an executable binary or shell script. A single program or script can be used to control all transitions by examining the name by which it was called.

/etc/random.seed
  Random seed file read by the bootloader; updated on “hibernate”, “standby” and “suspend”.

/var/run/apmdev
  Default UNIX-domain socket used for communication with apm(8).

# EXAMPLES

/etc/apm/suspend

      # X11 screen lock
      pkill -USR1 xidle

/etc/apm/warnlow

      # low battery notifications
      aucat -i /etc/apm/tired.wav

# SEE ALSO

syslog(3), apm(4), apm(8), sysctl(8)

Advanced Power Management (APM) BIOS Interface Specification (revision 1.2), Intel Corporation and Microsoft Corporation.

# HISTORY

The `apmd` command first appeared in NetBSD 1.3. OpenBSD support was added in OpenBSD 1.2.

# CAVEATS

`apmd` does not support specifying an alternate performance policy to be used when the system is running on battery. See the hw.perfpolicy setting documented in sysctl(2).

June 1, 2025 | Debian