can i change the polling frequency of a running ntpd?

Question

I've got ntpd running.  It's been running for a while, and the polling frequency is up to the max of 1024

remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*time.local      132.163.4.102    2 u  813 1024  377    0.109   -0.209   0.342

For whatever reason, I would like to set the polling frequency back to 128 sec.  I don't mind if, after it does 128 sec for a while, it follows its usual plan of increasing the poll frequency back to 1024.  But right now, at this moment, I want it at 128.

Is there a way to do that?  The only way I know is to restart ntpd.

Paul Gear · Answer

It would be theoretically possible if you had configured authentication keys ahead of time in /etc/ntp.conf, found the association id with ntpq, and used the writevar command on the association id to change the polling interval.

Except that the only association variable you're allowed to change at runtime is the leap second indicator.  See https://lists.ntp.org/pipermail/questions/2005-February/004382.html for an explanation of this and a pointer to the code that implements it.

In short, no it's not possible.  Why do you think you want to change the polling interval anyway?

user3788685 · Answer

Yes - but you will need to restart ntpd to reload the config.

Have a look at the docs here.

You can set two options minpoll n and maxpoll n which you can adjust to give you the desired upper and lower limits.

These options specify the minimum and maximum poll intervals for NTP
  messages, in seconds to the power of two. The maximum poll interval
  defaults to 10 (1,024 s), but can be increased by the maxpoll option
  to an upper limit of 17 (36.4 h). The minimum poll interval defaults
  to 6 (64 s), but can be decreased by the minpoll option to a lower
  limit of 4 (16 s).

For example in my config I list;

server 127.127.28.1 minpoll 4 which polls my gps pps every 16sec.

minpoll & maxpoll cal be used together.

I don't believe there is any way to reduce the poll frequency 'now' and have it work back up to 1024 but you can reduce it and keep it within a more desired window.

can i change the polling frequency of a running ntpd?

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