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 help text and exit.
-V | --version
Display version information and exit.
-n | --dry-run
This option does everything apart from actually setting up the
alarm, suspending the system, or waiting 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 adjtime file. 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 adjtime file.
-u | --utc
Assumes that the hardware clock is set to UTC (Universal Time
Coordinated), regardless of the contents of adjtime file.
-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".
FILES
/etc/adjtime
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@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)
util-linux July 2007 RTCWAKE(8)
Czas wygenerowania: 0.00013 sek.
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