rtcwake
enter a system sleep state until specified wakeup time
see also :
hwclock - date
Synopsis
rtcwake
[-hvVluan] [-d device]
[-m standby_mode] {-t
time_t|-s seconds}
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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 a short help message
that shows how to use the program.
-V |
--version
Displays version information
and exists.
-n |
--dry-run
This option does everything but
actually setup alarm, suspend system or wait for the
alarm.
-a | --auto
Reads 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 | --local
Assumes that the hardware clock
is set to local time, regardless of the contents of
/etc/adjtime.
-u | --utc
Assumes that the hardware clock
is set to UTC (Universal Time Coordinated), regardless of
the contents of /etc/adjtime.
-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.
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".
availability
The rtcwake command is part of the util-linux package and is
available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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.
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.
see also
hwclock ,
date
author
The program was
written by David Brownell
<dbrownell[:at:]users.sourceforge[:dot:]net> and improved by
Bernhard Walle <bwalle[:at:]suse[:dot:]de>.