Linux下利用rtcwake喚醒裝置
轉自https://blog.csdn.net/bulreed/article/details/19907691
以下是在OpenSuse上所做的測試
whereis rtcwake
rtcwake: /usr/sbin/rtcwake /usr/share/man/man8/rtcwake.8.gz
rtcwake --help
Usage:
rtcwake [options]
Options:
-d, --device <device> select rtc device (rtc0|rtc1|...)
-n, --dry-run does everything, but suspend
-l, --local RTC uses local timezone
-m, --mode <mode> standby|mem|... sleep mode
-s, --seconds <seconds> seconds to sleep
-t, --time <time_t> time to wake
-u, --utc RTC uses UTC
-v, --verbose verbose messages
-h, --help display this help and exit
-V, --version output version information and exit
For more details see rtcwake(8).
standby
普通待機模式，為預設選項，對應ACPI state S1
mem
待機到記憶體，即記憶體之外把其他裝置都進入低功耗模式，對應ACPI state S3
disk
待機到硬碟，即休眠，把電腦的當前狀態儲存到硬碟，幾乎不消耗外部電源，對應ACPI state S4
off
通過呼叫系統的關機命令來休眠， 對應ACPI state S5
可以通過以下命令查閱當前系統支援的休眠模式
cat /sys/power/state
standby mem disk
我的電腦目前支援以上三種，但是測試發現休眠到disk的時候，機器會迅速醒來，standby和mem兩種模式則工作正常，箇中原因還不清楚。
執行該命令的時候需要root許可權
1. 系統休眠後20seconds喚醒，加-v選項可以看到更多的列印資訊
sudo rtcwake -v -s 20 -m mem 或
sudo rtcwake -v -s 20 -m standby
列印資訊:
rtcwake -v -s 20 -m mem
Using UTC time.
delta = 0
tzone = 0
tzname = UTC
systime = 1393296617, (UTC) Tue Feb 25 02:50:17 2014
rtctime = 1393296617, (UTC) Tue Feb 25 02:50:17 2014
alarm 0, sys_time 1393296617, rtc_time 1393296617, seconds 20
rtcwake: wakeup from "mem" using /dev/rtc0 at Tue Feb 25 02:50:38 2014
suspend mode: mem; suspending system
2. 系統在指定的時間醒來
rtcwake -v -t `date -d 10:53 +%s` -m mem
Using UTC time.
delta = 0
tzone = 0
tzname = UTC
systime = 1393296754, (UTC) Tue Feb 25 02:52:34 2014
rtctime = 1393296754, (UTC) Tue Feb 25 02:52:34 2014
alarm 1393296780, sys_time 1393296754, rtc_time 1393296754, seconds 0
rtcwake: wakeup from "mem" using /dev/rtc0 at Tue Feb 25 02:53:00 2014
suspend mode: mem; suspending system
rtcwake -v -t `date -d 10:54 +%s` -m standby
Using UTC time.
delta = 0
tzone = 0
tzname = UTC
systime = 1393296794, (UTC) Tue Feb 25 02:53:14 2014
rtctime = 1393296794, (UTC) Tue Feb 25 02:53:14 2014
alarm 1393296840, sys_time 1393296794, rtc_time 1393296794, seconds 0
rtcwake: wakeup from "standby" using /dev/rtc0 at Tue Feb 25 02:54:00 2014
suspend mode: standby; suspending system
如果發現systime 和rtctime時間不一致，需要利用hwclock進行調整。