Real-time clock alarm

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A real time clock alarm is a feature that can be used to allow a computer to 'wake up' after shut down to execute tasks every day or on a certain day. It can sometimes be found in the 'Power Management' section of a motherboard's BIOS setup. However, newer BIOS setups do not include an RTC alarm option, although it can still be set from within user applications. Wake On LAN, Wake on ring, and IPMI functions could also be used to start a computer after it is turned off.

In Linux, the real time clock alarm can be set or retrieved using /proc/acpi/alarm or /sys/class/rtc/rtc0/wakealarm.[1] Alternatively the rtcwake utility may be used which prevents problems when using local time instead of UTC by automatically processing the /etc/adjtime file. systemd can be used to wake a system and run a task at a specific time.[2]

In Microsoft Windows there are different programs which could be used to 'wake up' a computer from standby or hibernation. Task Scheduler settings for power management can be used to 'Wake the computer to run this task'.


  1. ^ "ACPI Wakeup - MythTV Official Wiki".
  2. ^ "systemd.timer". Retrieved 27 October 2014.

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