1RTCWAKE(8) System Administration RTCWAKE(8)
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6 rtcwake - enter a system sleep state until specified wakeup time
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9 rtcwake [options] [-d device] [-m standby_mode] {-t time_t|-s seconds}
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12 This program is used to enter a system sleep state until specified
13 wakeup time.
14 This uses cross-platform Linux interfaces to enter a system sleep
16 state, and leave it no later than a specified time. It uses any RTC
17 framework driver that supports standard driver model wakeup flags.
18 This is normally used like the old apmsleep utility, to wake from a
20 suspend state like ACPI S1 (standby) or S3 (suspend-to-RAM). Most
21 platforms can implement those without analogues of BIOS, APM, or ACPI.
22 On some systems, this can also be used like nvram-wakeup, waking from
24 states like ACPI S4 (suspend to disk). Not all systems have persistent
25 media that are appropriate for such suspend modes.
26 Options
28 -v | --verbose
29 Be verbose.
30 -h | --help
32 Display a short help message that shows how to use the program.
33 -V | --version
35 Displays version information and exists.
36 -n | --dry-run
38 This option does everything but actually setup alarm, suspend
39 system or wait for the alarm.
40 -A | --adjfile file
42 Specifies an alternative path to the adjust file.
43 -a | --auto
45 Reads the clock mode (whether the hardware clock is set to UTC
46 or local time) from /etc/adjtime. That's the location where the
47 hwclock(8) stores that information. This is the default.
48 -l | --local
50 Assumes that the hardware clock is set to local time, regardless
51 of the contents of /etc/adjtime.
52 -u | --utc
54 Assumes that the hardware clock is set to UTC (Universal Time
55 Coordinated), regardless of the contents of /etc/adjtime.
56 -d device | --device device
58 Uses device instead of rtc0 as realtime clock. This option is
59 only relevant if your system has more than one RTC. You may
60 specify rtc1, rtc2, ... here.
61 -s seconds | --seconds seconds
63 Sets the wakeup time to seconds in future from now.
64 -t time_t | --time time_t
66 Sets the wakeup time to the absolute time time_t. time_t is the
67 time in seconds since 1970-01-01, 00:00 UTC. Use the date(1)
68 tool to convert between human-readable time and time_t.
69 -m mode | --mode mode
71 Use standby state mode. Valid values are:
72 standby
74 ACPI state S1. This state offers minimal, though real,
75 power savings, while providing a very low-latency transi‐
76 tion back to a working system. This is the default mode.
77 mem ACPI state S3 (Suspend-to-RAM). This state offers signif‐
79 icant power savings as everything in the system is put
80 into a low-power state, except for memory, which is
81 placed in self-refresh mode to retain its contents.
82 freeze The processes are frozen, all the devices are suspended
84 and all the processors idles. This state is a general
85 state that does not need any platform specific support,
86 but it saves less power than susepnd to RAM, because the
87 system is still in a running state. (since Linux 3.9)
88 disk ACPI state S4 (Suspend-to-disk). This state offers the
90 greatest power savings, and can be used even in the
91 absence of low-level platform support for power manage‐
92 ment. This state operates similarly to Suspend-to-RAM,
93 but includes a final step of writing memory contents to
94 disk.
95 off ACPI state S5 (Poweroff). This is done by calling
97 '/sbin/shutdown'. Not officially supported by ACPI, but
98 usually working.
99 no Don't suspend. The rtcwake command sets RTC wakeup time
101 only.
102 on Don't suspend, but read RTC device until alarm time
104 appears. This mode is useful for debugging.
105 disable
107 Disable previously set alarm.
108 show Print alarm information in format: "alarm: off|on
110 <time>". The time is in ctime() output format, e.g.
111 "alarm: on Tue Nov 16 04:48:45 2010".
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114 Some PC systems can't currently exit sleep states such as mem using
115 only the kernel code accessed by this driver. They need help from
116 userspace code to make the framebuffer work again.
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119 The program was posted several times on LKML and other lists before
120 appearing in kernel commit message for Linux 2.6 in the GIT commit
121 87ac84f42a7a580d0dd72ae31d6a5eb4bfe04c6d.
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124 The rtcwake command is part of the util-linux package and is available
125 from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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128 The program was written by David Brownell <dbrownell@users.source‐
129 forge.net> and improved by Bernhard Walle <bwalle@suse.de>.
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132 This is free software. You may redistribute copies of it under the
133 terms of the GNU General Public License
134 <http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the
135 extent permitted by law.
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138 hwclock(8), date(1)
139util-linux July 2007 RTCWAKE(8)