NAME

       rtcwake - enter a system sleep state until specified wakeup time

SYNOPSIS

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

DESCRIPTION

       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.

   Options
       -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.

       -t time_t | --time time_t
              Sets  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.

       -m mode | --mode mode
              Use standby state mode. Valid values 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.

              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 usually working.

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

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

              disable
                     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".

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.

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.

AVAILABILITY

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

AUTHOR

       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)