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.\" Copyright (c) 2007, SUSE LINUX Products GmbH
.\" Bernhard Walle <>
.\" This program is free software; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License
.\" as published by the Free Software Foundation; either version 2
.\" of the License, or (at your option) any later version.
.\" This program is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" GNU General Public License for more details.
.\" You should have received a copy of the GNU General Public License
.\" along with this program; if not, write to the Free Software
.\" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
.\" 02110-1301, USA.
.TH rtcwake 8 "2007-07-13" "" "Linux Programmer's Manual"
rtcwake - enter a system sleep state until specified wakeup time
.B rtcwake
.RB [ \-hvVlua ]
.RB [ \-d
.IR device ]
.RB [ \-m
.IR standby_mode ]
.RB { "\-t \fItime_t\fP" | "\-s \fIseconds\fP" }
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 \fBapmsleep\fP 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 \fBnvram-wakeup\fP, waking from states
like ACPI S4 (suspend to disk). Not all systems have persistent media that are
appropriate for such suspend modes.
.SS Options
\fB-v\fP | \fB--verbose\fP
Be verbose.
\fB-h\fP | \fB--help\fP
Display a short help message that shows how to use the program.
\fB-V\fP | \fB--version\fP
Displays version information and exists.
\fB-a\fP | \fB--auto\fP
Reads the clock mode (whether the hardware clock is set to UTC or local time)
from \fI/etc/adjtime\fP. That's the location where the
.BR hwclock (8)
stores that information.
\fB-l\fP | \fB--local\fP
Assumes that the hardware clock is set to local time, regardless of the
contents of \fI/etc/adjtime\fP.
\fB-u\fP | \fB--utc\fP
Assumes that the hardware clock is set to UTC (Universal Time Coordinated),
regardless of the contents of \fI/etc/adjtime\fP.
\fB-d\fP \fIdevice\fP | \fB--device\fP \fIdevice\fP
Uses \fIdevice\fP instead of \fIrtc0\fP as realtime clock. This option
is only relevant if your system has more than one RTC. You may specify
\fIrtc1\fP, \fIrtc2\fP, ... here.
\fB-s\fP \fIseconds\fP | \fB--seconds\fP \fIseconds\fP
Sets the wakeup time to \fIseconds\fP in future from now.
\fB-t\fP \fItime_t\fP | \fB--time\fP \fItime_t\fP
Sets the wakeup time to the absolute time \fItime_t\fP. \fItime_t\fP
is the time in seconds since 1970-01-01, 00:00 UTC. Use the
.BR date (1)
tool to convert between human-readable time and \fItime_t\fP.
\fB-m\fP \fImode\fP | \fB--mode\fP \fImode\fP
Use standby state \fImode\fP. Valid values are:
.B 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.
.B 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.
.B 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.
.B off
ACPI state S5 (Poweroff). This is done by calling '/sbin/shutdown'.
Not officially supported by ACPI, but usually working.
.B no
Don't suspend. The rtcwake command sets RTC wakeup time only.
.B on
Don't suspend, but read RTC device until alarm time appears. This mode is
useful for debugging.
Some PC systems can't currently exit sleep states such as \fImem\fP
using only the kernel code accessed by this driver.
They need help from userspace code to make the framebuffer work again.
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.
The rtcwake command is part of the util-linux-ng package and is available from
The program was written by David Brownell <>
and improved by Bernhard Walle <>.
This is free software. You may redistribute copies of it under the terms
of the GNU General Public License <>.
There is NO WARRANTY, to the extent permitted by law.
.BR hwclock (8),
.BR date (1)