Ubuntu Manpage: rtcwake - enter a system sleep state until specified wakeup time

Provided by: util-linux_2.34-0.1ubuntu9.6_amd64

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 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.

-V, --version
Display version information and exit.

-h, --help
Display help text 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.

AVAILABILITY

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