[ntp:questions] Testing Sync Across Several Systems

Jan Ceuleers janspam.ceuleers at skynet.be
Mon Jul 20 13:21:45 UTC 2009

T wrote:
> We have about 50 Linux/Solaris/Windows boxes running ntpd at several
> different sites. Some of the systems from time to time go out of sync.
> My question is there a way to test ntpd machines are all in sync with
> the master
> server?

The easiest way I can think of is to poll those machines using ntpd from a monitoring host.

This monitoring host's ntpd.conf contains, for each of your to-be-monitored boxes, a line like the following:

   server box1thru50.domain.tld noselect

So that's about 50 lines like the above, in addition to your normal server lines (since the monitoring host itself also needs to be synced to the "master server"). (In fact, it might _be_ the "master server"). The "noselect" option on the server lines tells your monitoring host to only poll that box but never to try syncing to it itself.

Then you can inspect the state of play using ntpq:

   ntpq -p monitoringhost.domain.tld

This assumes that the to-be-monitored boxes have static IP addresses (or else you would need to restart the monitoring host's ntpd periodically). It also assumes (I've never tried it) that ntpd will scale to the number of hosts that you want to monitor.

If you need anything more elaborate, google for "ntp survey". There is a periodic project run by Brazilian academics whose toolset you might be able to reuse.

Cheers, Jan

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