Codex

RTCWAKE

Section: System Administration (8)

Updated: July 2007

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NAME

rtcwake - enter a system sleep state until specified wakeup time

SYNOPSIS

rtcwake [options] [-d device] [-m standby_mode] {-t time_t|-s seconds}

DESCRIPTION

This program is used to enter a system sleep state until specified wakeup time.

This uses cross-platform Linux interfaces to enter a system sleep state, and leave it no later than a specified time. It uses any RTC framework driver that supports standard driver model wakeup flags.

This is normally used like the old apmsleep utility, to wake from a suspend state like ACPI S1 (standby) or S3 (suspend-to-RAM). Most platforms can implement those without analogues of BIOS, APM, or ACPI.

On some systems, this can also be used like nvram-wakeup, waking from states like ACPI S4 (suspend to disk). Not all systems have persistent media that are appropriate for such suspend modes.

Options

-v | --verbose
Be verbose.:
-h | --help
Display help text and exit.:
-V | --version
Display version information and exit.:
-n | --dry-run
This option does everything apart from actually setting up the alarm, suspending the system, or waiting for the alarm.:
-A | --adjfile file
Specifies an alternative path to the adjust file.:
-a | --auto
Reads the clock mode (whether the hardware clock is set to UTC or local time) from adjtime file. That's the location where the hwclock?(8) stores that information. This is the default.:
-l | --local
Assumes that the hardware clock is set to local time, regardless of the contents of adjtime file.:
-u | --utc
Assumes that the hardware clock is set to UTC (Universal Time Coordinated), regardless of the contents of adjtime file.:
-d device | --device device
Uses device instead of rtc0 as realtime clock. This option is only relevant if your system has more than one RTC. You may specify rtc1, rtc2, ... here.:
-s seconds | --seconds seconds
Sets the wakeup time to seconds in future from now.:
-t time_t | --time time_t
Sets the wakeup time to the absolute time time_t. time_t is the time in seconds since 1970-01-01, 00:00 UTC. Use the date?(1) tool to convert between human-readable time and time_t.:
-m mode | --mode mode
Use standby state mode. Valid values are:

:

standby
ACPI state S1. This state offers minimal, though real, power savings, while providing a very low-latency transition back to a working system. This is the default mode.:
mem
ACPI state S3 (Suspend-to-RAM). This state offers significant power savings as everything in the system is put into a low-power state, except for memory, which is placed in self-refresh mode to retain its contents.:
freeze
The processes are frozen, all the devices are suspended and all the processors idles. This state is a general state that does not need any platform specific support, but it saves less power than susepnd to RAM, because the system is still in a running state. (since Linux 3.9):
disk
ACPI state S4 (Suspend-to-disk). This state offers the greatest power savings, and can be used even in the absence of low-level platform support for power management. This state operates similarly to Suspend-to-RAM, but includes a final step of writing memory contents to disk.:
off
ACPI state S5 (Poweroff). This is done by calling '/sbin/shutdown'. Not officially supported by ACPI, but usually working.:
no
Don't suspend. The rtcwake command sets RTC wakeup time only.:
on
Don't suspend, but read RTC device until alarm time appears. This mode is useful for debugging.:
disable
Disable previously set alarm.:
show
Print alarm information in format: "alarm: off|on <time>". The time is in ctime() output format, e.g. "alarm: on Tue Nov 16 04:48:45 2010".:

FILES

/etc/adjtime

NOTES

Some PC systems can't currently exit sleep states such as mem using only the kernel code accessed by this driver. They need help from userspace code to make the framebuffer work again.

HISTORY

The program was posted several times on LKML and other lists before appearing in kernel commit message for Linux 2.6 in the GIT commit 87ac84f42a7a580d0dd72ae31d6a5eb4bfe04c6d.

AVAILABILITY

The rtcwake command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

AUTHOR

The program was written by David Brownell <[email protected]> and improved by Bernhard Walle <[email protected]>.

COPYRIGHT

This is free software. You may redistribute copies of it under the terms of the GNU General Public License <http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

hwclock?(8), date?(1)


Index

NAME

SYNOPSIS

DESCRIPTION

Options

FILES

NOTES

HISTORY

AVAILABILITY

AUTHOR

COPYRIGHT

SEE ALSO