The RTC remembers its time set, and how does the linux kernel gets this time from dev/rtc and set it as the linux time. In other words on boot up - when does kernel reads the rtc and updates its linux time.


Linux kernel has following option RTC_HCTOSYS to restore system time from RTC on startup.

If you say yes here, the system time (wall clock) will be set using the value read from a specified RTC device. This is useful to avoid unnecessary fsck runs at boot time, and to network better.

Another way is to use a startup script, that will use hwclock utility to set system time from RTC.

hwclock --hctosys
  • simply running the hwclock , syncs the rtc clock to that of the linux. – jebina Feb 4 '14 at 5:53

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