rtcwake

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 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.

SEE ALSO
       hwclock(8), date(1)

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/⟩.



util-linux                          June 2015                         RTCWAKE(8)