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] {-s seconds|-t time_t}
DESCRIPTION
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.
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 the terminal to settle down before
entering a system sleep.
OPTIONS
-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
timestamp can be any of the following:
┌────────────────────┬───────────────────────────┐
│ │ │
│YYYYMMDDhhmmss │ │
├────────────────────┼───────────────────────────┤
│ │ │
│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) │
├────────────────────┼───────────────────────────┤
│ │ │
│+5min │ │
└────────────────────┴───────────────────────────┘
-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-modes
List available --mode option arguments.
-m, --mode mode
Go into the given standby state. Valid values for mode 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.
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
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".
-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(1) 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.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
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.
FILES
/etc/adjtime
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.
AUTHORS
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
adjtime_config(5), hwclock(8), date(1)
REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
AVAILABILITY
The rtcwake command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>.
util-linux 2.38.1 2022-05-11 RTCWAKE(8)
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