rtcwake(8)                                          Linux Programmer's Manual                                         rtcwake(8)



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  loca-
              tion 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.

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 available from ftp://ftp.kernel.org/pub/linux/utils/util-
       linux-ng/.

AUTHOR
       The  program  was  written  by  David  Brownell  <dbrownellATusers.net>  and  improved   by   Bernhard   Walle
       <bwalleATsuse.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)