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

Provided by: util-linux_2.27.1-6ubuntu3.10_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.

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 timestmap 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
       ⟨ftp://ftp.kernel.org/pub/linux/utils/util-linux/⟩.