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SubjectRe: PROBLEM: Linux updates RTC secretly when clock synchronizes
Hi!

> PROBLEM: Linux updates RTC secretly when clock synchronizes.
>
> Please CC replies etc to Ian Maclaine-cross <iml@debian.org>.
>
> When /usr/sbin/ntpd synchronizes the Linux kernel (or system) clock
> using the Network Time Protocol the kernel time is accurate to a few
> milliseconds. Linux then sets the Real Time (or Hardware or CMOS)
> Clock to this time at approximately 11 minute intervals. Typical RTCs
> drift less than 10 s/day so rebooting causes only millisecond errors.
>
> Linux currently does not record the 11 minute updates to a log file.
> Clock programs (like hwclock) cannot correct RTC drift at boot without
> knowing when the RTC was last set. If NTP service is available after a
> long shutdown, ntpd may step the time. Worse after a longer shutdown
> ntpd may drop out or even synchronize to the wrong time zone. The
> workarounds are clumsy.
>
> Please find following my small patch for linux/arch/i386/kernel/time.c
> which adds a KERN_NOTICE of each 11 minute update to the RTC. This is
> just for i386 machines at present. A script can search the logs for
> the last set time of the RTC and update /etc/adjtime. Hwclock can
> then correct the RTC for drift and set the kernel clock.

That seems as very wrong solution.

What about just making kernel only _read_ system clock, and never set it?
That looks way cleaner to me.

Pavel
--
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.

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