rtcwake

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] {-s seconds|-t time_t}

DESCRIPTION
       This program is used to enter a system sleep state and to automatically
       wake from it at a specified 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.

       Note that alarm functionality depends on hardware;  not  every  RTC  is
       able to setup an alarm up to 24 hours in the future.

       The  suspend  setup  may be interrupted by active hardware; for example
       wireless USB input devices that continue to send events for some  frac-
       tion  of  a  second  after the return key is pressed.  rtcwake tries to
       avoid this problem and it waits to terminal to settle down  before  en-
       tering a system sleep.

OPTIONS
       -A, --adjfile file
              Specify an alternative path to the adjust file.

       -a, --auto
              Read the clock mode (whether the hardware clock is set to UTC or
              local time) from the adjtime file, where hwclock(8) stores  that
              information.  This is the default.

       --date timestamp
              Set  the  wakeup  time to the value of the timestamp.  Format of
              the timestamp can be any of the following:

              YYYYMMDDhhmmss
              YYYY-MM-DD hh:mm:ss
              YYYY-MM-DD hh:mm     (seconds will be set to 00)
              YYYY-MM-DD           (time will be set to 00:00:00)
              hh:mm:ss             (date will be set to today)
              hh:mm                (date will be set to today, seconds to 00)
              tomorrow             (time is set to 00:00:00)
              +5min

       -d, --device device
              Use the specified 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.

       -l, --local
              Assume that the hardware clock is set to local time,  regardless
              of the contents of the adjtime file.

       --list-modes
              List available --mode option arguments.

       -m, --mode mode
              Go into the given standby state.  Valid values for mode 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.

              freeze The  processes  are frozen, all the devices are suspended
                     and all the processors idled.  This state  is  a  general
                     state  that  does not need any platform-specific support,
                     but it saves less power than Suspend-to-RAM, because  the
                     system  is  still  in  a running state.  (Available since
                     Linux 3.9.)

              mem    ACPI state S3 (Suspend-to-RAM).  This state  offers  sig-
                     nificant 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  ab-
                     sence of low-level platform support for power management.
                     This state operates similarly to Suspend-to-RAM, but  in-
                     cludes 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
                     it usually works.

              no     Don't suspend, only set the RTC wakeup time.

              on     Don't  suspend,  but  read  the RTC device until an alarm
                     time appears.  This mode is useful for debugging.

              disable
                     Disable a 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".

       -n, --dry-run
              This option does everything apart from actually setting  up  the
              alarm, suspending the system, or waiting for the alarm.

       -s, --seconds seconds
              Set the wakeup time to seconds in the future from now.

       -t, --time time_t
              Set  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.

       -u, --utc
              Assume that the hardware clock is set to UTC (Universal Time Co-
              ordinated), regardless of the contents of the adjtime file.

       -v, --verbose
              Be verbose.

       -V, --version
              Display version information and exit.

       -h, --help
              Display help text and exit.

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.

FILES
       /etc/adjtime

HISTORY
       The program was posted several times on LKML and other lists before ap-
       pearing  in  kernel  commit  message  for  Linux  2.6 in the GIT commit
       87ac84f42a7a580d0dd72ae31d6a5eb4bfe04c6d.

AUTHORS
       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/li-
       censes/gpl.html>.   There  is  NO  WARRANTY, to the extent permitted by
       law.

SEE ALSO
       hwclock(8), date(1)

AVAILABILITY
       The rtcwake command is part of the util-linux package and is  available
       from  the  Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux                         June 2015                        RTCWAKE(8)