Hello again Thierry, On Tuesday, February 12, 2008 at 10:58:32 +0100, Thierry MARTIN wrote:
> Can anyone tell me if a time shift greater than 2s per day is > ""normal"" on a linux system that has no "external" synchronisation > (ntp)? Absolutely normal: that's only 23 PPM, nothing. I have seen machines that do better, and some that do much worse. As long as it's stable, 2 secs/day every day, and below 500 PPM, it's zeroifiable via the kernel clock frequency setting. Even above 500 PPM, with help from --tick. > I tryied "adjtimex -a" which gives unreliable results This --adjust thing is quite reliable, easely to the single PPM (less than 0.1 secs/day), provided you already carefully calibrated its reference: The RTC, via hwclock and /etc/adjtime. There are plenty of other methods to get an accurate kernel clock frequency. I'll propose one: run ntpd on the machine during some hours or a day, with a good connection to (a) good server(s). Then the following days restore the wanted kernel frequency via: | # ntptime -f $(cat /var/lib/ntp/ntp.drift) > /dev/null Or via: | # adjtimex --frequency $(awk '{printf "%.0f", $1 * 65536; exit}' /var/lib/ntp/ntp.drift) Cordialement, Serge. -- Serge point Bets arobase laposte point net _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions