Messages in this thread |  | | Date | Fri, 2 Nov 2001 12:16:03 +0000 | From | Pavel Machek <> | Subject | Re: PROBLEM: Linux updates RTC secretly when clock synchronizes |
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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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