rtcwake [-hvVluan] [-d device] [-m standby_mode] {-t time_t|-s seconds}

       This  program  is  used  to  enter a system sleep state until specified
       wakeup 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.

       -v | --verbose
              Be verbose.

       -h | --help
              Display a short help message that shows how to use the program.

       -V | --version
              Displays version information and exists.

       -n | --dry-run
              This option does everything but actually  setup  alarm,  suspend
              system or wait for the alarm.

       -a | --auto
              Reads  the  clock mode (whether the hardware clock is set to UTC
              or local time) from /etc/adjtime. That's the location where  the
              hwclock(8) stores that information. This is the default.

       -l | --local
              Assumes that the hardware clock is set to local time, regardless
              of the contents of /etc/adjtime.

       -u | --utc
              Assumes that the hardware clock is set to  UTC  (Universal  Time
              Coordinated), regardless of the contents of /etc/adjtime.

       -d device | --device device
              Uses  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.

       -s seconds | --seconds seconds
              Sets the wakeup time to seconds in future from now.
                     tion back to a working system. This is the default mode.

              mem    ACPI state S3 (Suspend-to-RAM). This state offers signif-
                     icant 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  manage-
                     ment.  This  state  operates similarly to Suspend-to-RAM,
                     but includes a final step of writing memory  contents  to

              off    ACPI  state  S5  (Poweroff).  This  is  done  by  calling
                     '/sbin/shutdown'.  Not officially supported by ACPI,  but
                     usually working.

              no     Don't  suspend.  The rtcwake command sets RTC wakeup time

              on     Don't suspend, but  read  RTC  device  until  alarm  time
                     appears. This mode is useful for debugging.

                     Disable 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".

       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.

       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

       The  rtcwake command is part of the util-linux package and is available
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

       The program was  written  by  David  Brownell  <dbrownell@users.source-
       forge.net> and improved by Bernhard Walle <bwalle@suse.de>.

       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.
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