[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
>>>>> associated
>>>>> 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
>>> accurately.
>> 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 prefer minpoll 3 maxpoll 6 mode 72
> fudge 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
> Sincerely,
> Ron
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
shameless advantage.

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.

More information about the questions mailing list