rtcwake man page on Ubuntu

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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)
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