[ntp:questions] Change poll interval at runtime?
Richard B. Gilbert
rgilbert88 at comcast.net
Sun Feb 26 23:09:24 UTC 2012
On 2/26/2012 12:55 AM, Ron Frazier (NTP) wrote:
> On 2/25/2012 5:05 PM, A C wrote:
>> On 2/25/2012 13:09, Richard B. Gilbert wrote:
>>> On 2/25/2012 1:20 AM, A C wrote:
>>>> On 2/24/2012 21:26, A C wrote:
>>>>> Is it possible to change the polling interval of one or more
>>>>> servers at runtime? It seems like I should be able to run:
>>>>> ntpq -c "writevar &associd hpoll=N" or is it ppoll?
>>>> Actually, I should have been more specific and say change the minimum
>>>> polling interval. In other words, be able to adjust the conf file's
>>>> minpoll flag at runtime instead of restarting.
>>> What problem are you trying to solve?
>>> NTPD does a pretty good job of adjusting itself most of the time.
>>> Short poll intervals are useful when correcting large errors.
>>> Long poll intervals allow NTPD to make small corrections very
>> The idea was to bump up the minimum poll interval after ntpd has been
>> running for a day or so to something more kind to the remote servers
>> because the refclock is holding the remote servers clamped to 64
>> seconds. If I set minpoll in the config file, then ntpd's start up
>> takes a long time because of a long poll interval. If I don't set the
>> minpoll, then ntpd doesn't do "a pretty good job" because it clamps
>> the polling interval.
> I've noticed the same thing. You could try what I'm doing, although I'm
> still testing for the best configuration.
> # GPS Lines
> server 127.127.20.5 prefer minpoll 3 maxpoll 6 mode 72
> fudge 127.127.20.5 time2 0.3100 refid GPS1
> # Internet server lines
> # NIST New York
> server nist1-ny.ustiming.org minpoll 8 maxpoll 13
> # other internet server lines similar
NTPD adjusts the poll interval dynamically. Just because MINPOLL=4 does
not mean that the poll interval is "stuck" there. Give NTPD a
rock solid 1 second per second source it will ramp up the poll interval
to 1024 seconds. Those "rock solid" ticks can frequently be found
1:00AM to 5:00AM local time. The net quiets down and NTPD takes
If you really want good time and can afford a GPS *timing* receiver
that's the way to do it. The last I heard, you could get a timing
receiver for $100 -- $300.
ANY GPS receiver knows what time it is but the navigation receivers
give priority to location. Timing receivers give priority to delivering
the correct time.
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