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RTCWAKE(8)                   System Administration                  RTCWAKE(8)

NAME
       rtcwake - enter a system sleep state until specified wakeup time
SYNOPSIS
       rtcwake [options] [-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 | --adjfile file
              Specifies an alternative path to the adjust file.
       -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 /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.
              freeze The processes are frozen, all the devices  are  suspended
                     and  all  the  processors  idles. This state is a general
                     state that does not need any platform  specific  support,
                     but  it saves less power than susepnd to RAM, because the
                     system is still in a running state. (since Linux 3.9)
              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.
              disable
                     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".
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 package and is available
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
AUTHOR
       The program was  written  by  David  Brownell  <dbrownell AT users.source-
       forge.net> and improved by Bernhard Walle <bwalle AT 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)

util-linux                         July 2007                        RTCWAKE(8)