hardlink: use xcalloc rather than xmalloc

[thirdparty/util-linux.git] / sys-utils / rtcwake.8.adoc

//po4a: entry man manual
= rtcwake(8)
:doctype: manpage
:man manual: System Administration
:man source: util-linux {release-version}
:page-layout: base
:command: rtcwake

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

[cols=",",]
|===
|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 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*;;
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 Coordinated), regardless of the contents of the _adjtime_ file.

*-v*, *--verbose*::
Be verbose.

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== 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

_{ADJTIME_PATH}_

== 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.

== AUTHORS

The program was written by mailto:dbrownell@users.sourceforge.net[David Brownell] and improved by mailto:bwalle@suse.de[Bernhard Walle].

== COPYRIGHT

This is free software. You may redistribute copies of it under the terms of the link:http://www.gnu.org/licenses/gpl.html[GNU General Public License]. There is NO WARRANTY, to the extent permitted by law.

== SEE ALSO

*adjtime_config*(5),
*hwclock*(8),
*date*(1)

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