Please just ignore my questions as now my ntpd synchronises quite well with the ntp servers from the pool.
For what ever reasons, it seems that ntpd can not automatically adjust the clock tick. And I thought that I can manually adjust the clock tick only when I have an RTC as the clock reference to compare to, as suggested on http://support.ntp.org/bin/view/Support/ManualCalibration. But I just realised after posting the questions and read a little bit more about adjtimex, that I can actually set the clock tick manually without any side affect. So what I did was adding 25 clock ticks manually using adjtimex, and after that ntpd could carry on adjusting the frequency to compensate the drift. In case somebody would like to know, I got that 25 figure from the average drift per day in seconds divided by 8.64 seconds. In my case, that average drift per day is about 212.15 seconds, so the result of the division is about 24.55 and I just rounded it up to 25. Kind regards, Anto Aryanto Rachmad wrote: > Hello everybody, > > I am trying to have a stable system clock on my Xen based VPS, so I > installed ntpd. When I used ntpdate once a day, I noticed that the drift > is quite a lot. So after I use ntpd, based on the output on the syslog, > it seems that my system clock is drifting for about 2.3 seconds in 16 > minutes as below: > > Aug 22 19:14:59 myvhost ntpd[3688]: time reset +2.431644 s > Aug 22 19:15:28 myvhost ntpd[3688]: synchronized to 213.239.214.170, > stratum 2 > Aug 22 19:15:54 myvhost ntpd[3688]: synchronized to 213.133.108.253, > stratum 2 > Aug 22 19:16:42 myvhost ntpd[3688]: synchronized to 213.9.73.106, stratum 2 > Aug 22 19:30:45 myvhost ntpd[3688]: time reset +2.314923 s > Aug 22 19:31:01 myvhost ntpd[3688]: synchronized to 213.9.73.106, stratum 2 > Aug 22 19:31:43 myvhost ntpd[3688]: synchronized to 213.239.195.212, > stratum 2 > Aug 22 19:32:15 myvhost ntpd[3688]: synchronized to 213.9.73.106, stratum 2 > Aug 22 19:46:06 myvhost ntpd[3688]: time reset +2.275680 s > Aug 22 19:46:41 myvhost ntpd[3688]: synchronized to 213.9.73.106, stratum 2 > Aug 22 19:47:17 myvhost ntpd[3688]: synchronized to 213.133.108.253, > stratum 2 > Aug 22 19:48:04 myvhost ntpd[3688]: synchronized to 213.239.195.212, > stratum 2 > Aug 22 19:48:12 myvhost ntpd[3688]: synchronized to 213.9.73.106, stratum 2 > > From what I understood, ntp is used to compensate the drifting instead > of changing the clock as ntpdate does, which makes the system clock > jumps. But when I run the following command, I can see that ntp is doing > the same as ntpdate: > > # while true; do date; sleep 1; done > . > . > Sat Aug 22 19:30:41 CEST 2009 > Sat Aug 22 19:30:42 CEST 2009 > Sat Aug 22 19:30:46 CEST 2009 <-- jumps 4 seconds > Sat Aug 22 19:30:47 CEST 2009 > Sat Aug 22 19:30:48 CEST 2009 > . > . > Sat Aug 22 19:46:02 CEST 2009 > Sat Aug 22 19:46:03 CEST 2009 > Sat Aug 22 19:46:06 CEST 2009 <-- jumps 3 seconds > Sat Aug 22 19:46:07 CEST 2009 > Sat Aug 22 19:46:08 CEST 2009 > . > . > > I think the only way to prevent this kind of jumping clock affect, is to > adjust the kernel clock tick and frequency. On my server at home, I can > do that using the adjtimex. But on my VPS, I can not because I don't > have /dev/rtc or any rtc device. Is there any way to compensate the > clock tick and frequency without having /dev/rtc? > > I know that it is problematic to run ntpd on Xen domU, but could anybody > give me some suggestion to have a stable system clock? > > FYI, the only settings that I have tried are the followings: > > myvhost:~# cat /proc/sys/xen/independent_wallclock > 1 > myvhost:~# cat > /sys/devices/system/clocksource/clocksource0/current_clocksource > jiffies > > Thanks a lot in advance for your help. > > Kind regards, > > Anto > > > _______________________________________________ > questions mailing list > [email protected] > https://lists.ntp.org/mailman/listinfo/questions > > > _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
