rtcwake(8) — Linux manual page


RTCWAKE(8)                  System Administration                 RTCWAKE(8)

NAME         top

       rtcwake - enter a system sleep state until specified wakeup time

SYNOPSIS         top

       rtcwake [options] [-d device] [-m standby_mode] {-s seconds|-t

DESCRIPTION         top

       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

       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
       fraction of a second after the return key is pressed.  rtcwake tries
       to avoid this problem and it waits to terminal to settle down before
       entering a system sleep.

OPTIONS         top

       -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:

              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)

       -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 available --mode option arguments.

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

              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
                     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 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 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

       -u, --utc
              Assume that the hardware clock is set to UTC (Universal Time
              Coordinated), 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         top

       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         top


HISTORY         top

       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

AUTHORS         top

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

COPYRIGHT         top

       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         top

       hwclock(8), date(1)

AVAILABILITY         top

       The rtcwake command is part of the util-linux package and is
       available from the Linux Kernel Archive 

COLOPHON         top

       This page is part of the util-linux (a random collection of Linux
       utilities) project.  Information about the project can be found at 
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.  If you have a
       bug report for this manual page, send it to
       util-linux@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2020-07-14.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-07-14.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

util-linux                        June 2015                       RTCWAKE(8)

Pages that refer to this page: adjtime(5)adjtime_config(5)hwclock(8)