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       rtcwake - enter a system sleep state until specified wakeup time


       rtcwake [-hvVlua] [-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.

       -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.

       -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:

                     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

              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

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


       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-ng  package and is
       available from


       The      program      was      written      by      David      Brownell
       <>   and   improved  by  Bernhard  Walle


       This is free software.  You may redistribute copies of it   under   the
       terms      of       the       GNU      General      Public      License
       <>.  There is NO WARRANTY,  to  the
       extent permitted by law.


       hwclock(8), date(1)

                                  2007-07-13                        rtcwake(8)