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rtcwake — enter a system sleep state until specified wakeup time
rtcwake [options] [
−d device ] [
−m standby_mode ]
−t time_t | −s seconds
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.
−v | −−verboseBe verbose.
−h | −−helpDisplay help text and exit.
−V | −−versionDisplay version information and exit.
−n | −−dry−runThis option does everything apart from actually setting up the alarm, suspending the system, or waiting for the alarm.
−A | −−adjfile fileSpecifies an alternative path to the adjust file.
−a | −−autoReads the clock mode (whether the hardware clock
is set to UTC or local time) from /etc/adjtime. That's the location
where the hwclock(8) stores
that information. This is the default.
−l | −−localAssumes that the hardware clock is set to local
time, regardless of the contents of /etc/adjtime.
−u | −−utcAssumes that the hardware clock is set to UTC
(Universal Time Coordinated), regardless of the
contents of /etc/adjtime.
−d device | −−device deviceUses 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 secondsSets the wakeup time to seconds in future from
now.
−t time_t | −−time time_tSets 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 modeUse 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.
- ff
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.
nDon'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".
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.
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.
The rtcwake command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
The program was written by David Brownell <dbrownell@users.sourceforge.net> and improved by Bernhard Walle <bwalle@suse.de>.
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.
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Copyright (c) 2007, SUSE LINUX Products GmbH Bernhard Walle <bwallesuse.de> This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |