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
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.
Note that alarm functionality depends on hardware; not every RTC
is able to setup an alarm up to 24 hours in the future.
The suspend setup may be interrupted by active hardware; for
example wireless USB input devices that continue to send events for some
fraction of a second after the return key is pressed. rtcwake tries
to avoid this problem and it waits to terminal to settle down before
entering a system sleep.
-A, --adjfile file
Specify an alternative path to the adjust file.
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.
Set the wakeup time to the value of the timestamp. Format
of the timestamp can be any of the following:
||(seconds will be set to 00)
||(time will be set to 00:00:00)
||(date will be set to today)
||(date will be set to today, seconds to
||(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.
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
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.
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
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
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
ACPI state S5 (Poweroff). This is done by calling
'/sbin/shutdown'. Not officially supported by ACPI, but it usually
Don’t suspend, only set the RTC wakeup time.
Don’t suspend, but read the RTC device until an
alarm time appears. This mode is useful for debugging.
Disable a previously set alarm.
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".
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
-t, --time time_t
Set the wakeup time to the absolute time time_t
is the time in seconds since 1970-01-01, 00:00 UTC. Use the
tool to convert between human-readable time and
Assume that the hardware clock is set to UTC (Universal
Time Coordinated), regardless of the contents of the adjtime
Display version information and exit.
Display help text and exit.