rtcwake(8) - phpMan

RTCWAKE(8) System Administration RTCWAKE(8)

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 ana-
logues 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 | --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
/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), regard-
less 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 mem-
ory, which is placed in self-refresh mode to retain its contents.

freeze The processes are frozen, all the devices are suspended and all the proces-
sors 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 sav-
ings, 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".

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.ker-
nel.org/pub/linux/utils/util-linux/.

AUTHOR
The program was written by David Brownell <dbrownell AT users.net> and improved
by Bernhard Walle <bwalle AT 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.