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Linux 2.6 - man page for rtcwake (linux section 8)

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

       rtcwake - enter a system sleep state until specified wakeup time

       rtcwake [-hvVluan] [-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 ana-
       logues 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.

       -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

       -u | --utc
	      Assumes that the hardware clock is set to UTC (Universal Time Coordinated), regard-
	      less 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 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  mem-
		     ory, which is placed in self-refresh mode to retain its contents.

	      disk   ACPI  state  S4 (Suspend-to-disk). This state offers the greatest power sav-
		     ings, 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 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".

       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

       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.

       The rtcwake command is part of the util-linux package and is available from ftp://ftp.ker-

       The  program  was written by David Brownell <dbrownell@users.sourceforge.net> and improved
       by Bernhard Walle <bwalle@suse.de>.

       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.

       hwclock(8), date(1)

					    2007-07-13				       rtcwake(8)

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