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
<dbrownell@users.sourceforge.net> and improved by Bernhard Walle
<bwalle@suse.de>.
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)
