rtcwake Man page

RTCWAKE(8) System Administration RTCWAKE(8)


rtcwake – enter a system sleep state until specified wakeup time


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


This program is used to enter a system sleep state and to automatically
wake from it at a specified 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.


-A, –adjfile file
Specify an alternative path to the adjust file.

-a, –auto
Read the clock mode (whether the hardware clock is set to UTC or
local time) from the adjtime file, where hwclock(8) stores that
information. This is the default.

–date timestamp
Set the wakeup time to the value of the timestamp. Format of
the timestmap can be any of the following:

YYYY-MM-DD hh:mm:ss
YYYY-MM-DD hh:mm (seconds will be set to 00)
YYYY-MM-DD (time will be set to 00:00:00)
hh:mm:ss (date will be set to today)
hh:mm (date will be set to today, seconds to 00)
tomorrow (time is set to 00:00:00)

-d, –device device
Use the specified 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.

-l, –local
Assume that the hardware clock is set to local time, regardless
of the contents of the adjtime file.

List available –mode option arguments.

-m, –mode mode
Go into the given standby state. Valid values for mode are:

ACPI state S1. This state offers minimal, though real,
power savings, while providing a very low-latency transi‐
tion back to a working system. This is the default mode.

freeze The processes are frozen, all the devices are suspended
and all the processors idled. This state is a general
state that does not need any platform-specific support,
but it saves less power than Suspend-to-RAM, because the
system is still in a running state. (Available since
Linux 3.9.)

mem ACPI state S3 (Suspend-to-RAM). This state offers sig‐
nificant 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 manage‐
ment. This state operates similarly to Suspend-to-RAM,
but includes a final step of writing memory contents to

off ACPI state S5 (Poweroff). This is done by calling
‘/sbin/shutdown’. Not officially supported by ACPI, but
it usually works.

no Don’t suspend, only set the RTC wakeup time.

on Don’t suspend, but read the RTC device until an alarm
time appears. This mode is useful for debugging.

Disable a previously set alarm.

show Print alarm information in format: “alarm: off|on

-n, –dry-run
This option does everything apart from actually setting up the
alarm, suspending the system, or waiting for the alarm.

-s, –seconds seconds
Set the wakeup time to seconds in the future from now.

-t, –time time_t
Set 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
tool to convert between human-readable time and time_t.

-u, –utc
Assume that the hardware clock is set to UTC (Universal Time
Coordinated), regardless of the contents of the adjtime file.

-v, –verbose
Be verbose.

-V, –version
Display version information and exit.

-h, –help
Display help text and exit.

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

The program was written by David Brownell and improved by Bernhard Walle .


This is free software. You may redistribute copies of it under the
terms of the GNU General Public License
. There is NO WARRANTY, to the
extent permitted by law.


hwclock(8), date

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

util-linux June 2015 RTCWAKE(8)