*BASH User Commands Ubuntu 10.04.4 LTS Server coreutils
GNU/Linux
rtcwake(8)                 Linux Programmer's Manual                rtcwake(8)



NAME
       rtcwake - enter a system sleep state until specified wakeup time

SYNOPSIS
       rtcwake [-hvVlua] [-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.

       -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:

              standby
                     ACPI state S1. This state offers  minimal,  though  real,
                     power savings, while providing a very low-latency transi-
                     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
                     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.

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-ng package and is  avail-
       able from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.

AUTHOR
       The  program  was  written  by  David Brownell <dbrownell@users.source-
       forge.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)



                                  2007-07-13                        rtcwake(8)