[ntp:questions] Long term disciplining against 1PPS reference only

Charbonneau, André Andre.Charbonneau at nrc-cnrc.gc.ca
Mon Oct 22 13:36:21 UTC 2018

Thanks for the follow-up on this.
Yes, I did try what you suggested and indeed it now allows me to use minsane  = 0 and behaves as documented.
I opened a bug report for this:


Best regards,
From: questions <questions-bounces+andre.charbonneau=nrc-cnrc.gc.ca at lists.ntp.org> on behalf of Dan Drown <dan-ntp at drown.org>
Sent: Friday, October 19, 2018 4:47 PM
To: questions at lists.ntp.org
Subject: Re: [ntp:questions] Long term disciplining against 1PPS reference only

Quoting "Charbonneau, André" <Andre.Charbonneau at nrc-cnrc.gc.ca>:
> Recently I've been trying to get one of my NTP server (a Raspberry
> Pi), to stay synchronized to a 1PPS signal coming from a Rb clock
> over long periods of time when all other sources are unavailable.
> The NTP server on the RPi is configured to have a couple upstream
> stratum 2 servers, plus the 1PPS driver, and a local clock driver.
> Reading more about this, it is documented (Computer Network Time
> Synchronization 2nd edition, by D. L. Mills, section 3.11.4) that I
> should be using the following command to tell NTP to keep the 1PPS
> synchronization even if no other sources are present:
> "tos minsane 0"

Looks like this code was added around 2 years ago to ntpd/ntp_config.c:

                 case T_Minsane:
                         val = tos->value.d;
                         if ((int)tos->value.d < 1)
                                 tos->value.d = 1;
                         l_minsane = (int)tos->value.d;

I've verified that changing the minimum from 1 to 0 in that code lets
this feature work again.  Can you give that a try?
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