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 persis-
       tent 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 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.

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 <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)

								    2007-07-13								rtcwake(8)