[CentOS] C6: ntpd time reset +277092510.162464 s

Fri Aug 31 14:58:13 UTC 2012
Tom Grace <lists-in at deathbycomputers.co.uk>

On 31/08/12 15:34, Rainer Traut wrote:
> Am 31.08.2012 16:19, schrieb Tom Grace:
>> If the clock is wrong by (if I remember correctly) about 30 mins it will
>> take so long to drift back to being correct that NTPd gives up.
> Hmm, no it still does time resets in my tests iIf I set the clock -27s 
> of timesource.
> This happens:
> Aug 31 16:30:14 aitcsdb002 ntpd[6062]: time reset +27.006389 s

Ah, it turns out I was wrong about the 30 mins thing, that relates to
some other issue with NTP giving up and quitting if the clock is
drifting around too much.

>From the docs (paraphrased a bit):
Normally, the time is slewed if the offset is less than the step
threshold, which is 128 ms by default, and stepped if above the
threshold. If the step threshold is set to zero, all offsets are
stepped, regardless of value.

Note: Since the slew rate is limited to 0.5 ms/s, each second of
adjustment requires an amortization interval of 2000 s. Thus, an
adjustment of many seconds can take hours or days to amortize.