[ntp:questions] Re: NTP clients not syncing up to servers?

Ted Beatie ted at permabit.com
Tue Oct 11 20:25:49 UTC 2005

Tom, thank you for the in-depth reply.

> If ntpd finds an offset of more than 1000 seconds, it will
> terminate itself unless "-g" is present on the ntpd command
> line. In that case, it will make one such adjustment and will
> terminate itself if a second such adjustment is required.

I'm confused then;

  server-04:~# ps aux|grep ntpd
  root     389  0.0  0.1  2328 2320 ?      SL   Jun13   0:05 /usr/sbin/ntpd -g

This instance of ntpd has been running since Jun13.  Shouldn't it have
terminated by now?  (not that I want it to terminate..  what I want is
for it to say, "ok upstream server, I think you're on crack, but I'm
going to believe you anyway.")

> Also make sure that each ntpd instance has at least 4
> reliable, consistent, and _working_ lower-stratum servers
> configured before you even start ntpd for the first time.

What if we can't guarantee that?  The docs certainly seem to say that
the more the better, but that only one is actually required.  Some of
our deployments have public internet access, in which case, we can
populate the ntp.conf file on the gateway machines with as many servers
as we'd like.  But a fair number of our deployments don't have outbound
internet access, and have only one internal NTP server, if even that.
And yet, we still want at a minimum, for all of our machines to be in sync.

> In any case, you should make no judgments about whether
> ntpd is working properly or not until it has been running
> for several hours, sometimes 2 days or more on a previously
> unitialized system.

This is also a problem.  Given our situation, the gateways and servers
all get powered on at roughly the same time.  Ideally, what we would
like is for the servers to sync up to the gateways, no matter what they
think of the accuracy of them, just so that they are all in sync.  Then,
if the gateways themselves get more reliable information, from internal
or external upstream servers, that the whole system asjusts accordingly.


Ted Beatie                         Permabit, Inc.             ted at permabit.com
Sr. Systems Engineer       One Kendall Sq, Cambridge, MA       +1-617-995-9317

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