[ntp:questions] NTPd looses sync regularly / 12 hour intervals.

Michael Nielsen hael at tv2.dk
Fri Sep 10 09:44:34 UTC 2010


Here are some more details from the ntp logging - ntp_mon peerstats..

It's doesn't seem to be a interrupt creep, as the server is maintaining
time properly all day, except for 30 mins each day.

So I guess it's a program I need to look for, any ideas as to what I
should look for ?

Regards
   Mike.

55449 8029.459 10.7.100.27 9634 -0.002910845 0.000745249 0.014838494
0.000182297
55449 8043.473 10.7.100.28 9434 0.001379801 0.000747673 0.007061521
0.000157649
55449 8299.732 10.7.100.28 9434 0.001414736 0.000731931 0.005022575
0.000115537
55449 8555.991 10.7.100.28 9434 0.001414736 0.000731931 0.007541755
0.000068723
55449 8813.250 10.7.100.28 9434 0.001414736 0.000731931 0.009477517
0.000031755
55449 9056.494 10.7.100.27 9634 -0.002179427 0.000873918 0.014844999
0.000731418
55449 9070.508 10.7.100.28 9434 0.001414736 0.000731931 0.010334099
0.000040580
55449 9239.820 10.7.100.28 9434 0.001414736 0.000731931 0.010206775
43.473413580
55449 9498.080 10.7.100.28 9034 86.948205334 0.000737279 0.004326775
75.298106172
55449 9754.338 10.7.100.28 9034 86.948171299 0.000713359 0.003715583
61.480627575
55449 9994.579 10.7.100.27 9034 86.945547774 0.000796132 0.014833280
86.947727202
55449 10011.597 10.7.100.28 9034 86.948171299 0.000713359 0.005644196
43.473347566
55449 10029.614 10.7.100.28 9034 86.947986361 0.000411148 0.002904350
38.883661440
55449 10046.631 10.7.100.28 9034 86.947986361 0.000411148 0.001597708
35.495764148
55449 10062.648 10.7.100.28 9034 86.947984728 0.000403990 0.000880227
32.862691288
55449 10078.664 10.7.100.28 9034 86.947984728 0.000403990 0.000680422
0.000158151
55449 10093.679 10.7.100.28 9034 86.947984728 0.000403990 0.000700578
0.000124794
55449 10111.696 10.7.100.28 9034 86.947984728 0.000403990 0.000636477
0.000092856
55449 10126.712 10.7.100.28 9034 86.947984728 0.000403990 0.000652824
0.000060522
55449 10144.730 10.7.100.28 9034 86.947984728 0.000403990 0.000884035
0.000005692
55449 10160.746 10.7.100.28 9034 86.947984728 0.000403990 0.000954348
0.000006893
55449 10263.711 10.7.100.28 8034 0.000000000 0.000000000 0.000000000
4.000000000
55449 10265.714 10.7.100.28 9044 -0.000018194 0.000384368 7.937500957
0.000000954
55449 10280.728 10.7.100.28 9044 -0.000029944 0.000349054 3.937557685
0.000011750
55449 10298.746 10.7.100.28 9044 -0.000029944 0.000349054 1.937760424
0.000031646

-----Original Message-----
From: questions-bounces+hael=tv2.dk at lists.ntp.org
[mailto:questions-bounces+hael=tv2.dk at lists.ntp.org] On Behalf Of Martin
Burnicki
Sent: Wednesday, 8 September 2010 5:26 PM
To: questions at lists.ntp.org
Subject: Re: [ntp:questions] NTPd looses sync regularly / 12 hour
intervals.

Michael,

Michael Nielsen wrote:
> The logs on the systems that have problems usually show the following
> pattern
> 
> 
> Sep  7 17:43:48 sn ntpd[11721]: synchronized to 10.7.100.28, stratum 2
> Sep  7 17:57:51 sn ntpd[11721]: time reset +71.784598 s
> Sep  7 17:59:10 sn ntpd[11721]: synchronized to 10.7.100.27, stratum 2
> Sep  8 05:29:11 sn ntpd[11721]: no servers reachable
> Sep  8 05:34:37 sn ntpd[11721]: synchronized to 10.7.100.28, stratum 2
> Sep  8 05:35:52 sn ntpd[11721]: time reset +74.977115 s
> Sep  8 05:36:41 sn ntpd[11721]: synchronized to 10.7.100.28, stratum 2

This looks like some other program is called in cyclic intervals (~12
hours,
run by cron?) to simply set the time to match the time of some external
time source.

After this has happened the offset and jitter figures reported by "ntpq
-p"
should increase drastically, and about 15 minutes (or a certain number
of
polling intervals) after the system time has been stepped by the other
program the time is stepped back by ntpd, causing the "time reset"
messages.

If the reference time source used by the other program continuously
drifts
apart from the reference time source(s) used by ntpd then you should see
the amount of time reported by the "time reset"s increase or decrease
continuously.

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany

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