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.
-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 timestmap can be any of the following:
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.
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
transition back to a working system. This is the
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
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 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
<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 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(1) 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 file.
Display version information and exit.
Display help text and exit.
This page is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
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util-linux June 2015 RTCWAKE(8)