[ntp:questions] Ignore one server except in extreme conditions?

Richard B. Gilbert rgilbert88 at comcast.net
Thu Nov 17 01:41:13 UTC 2011

On 11/16/2011 12:47 AM, A C wrote:
> Is there a way to configure ntpd to ignore a particular clock unless
> there is no other choice? What I'm thinking is to ignore the GPS
> receiver NMEA data and use only the PPS plus Internet servers for most
> of the synchronization. But if the Internet servers go down, accept the
> GPS NMEA data for seconds numbering and let the tick be controlled by PPS.
> I guess I'm asking for something opposite to the "prefer" flag, a "not
> unless you have to" flag. The GPS does get selected among the various
> clock sources but it's the worst of the bunch with respect to jitter and
> offset. Those two wander all over while the rest of the Internet servers
> and the PPS are stable. It is almost never rejected as an outlier or
> false ticker even if it's way out of line with the other sources.

Which GPS receiver are you using?  I have an old Motorola that has been 
ticking away flawlessly for the last six or seven years.

I found that getting time over the internet was not very satisfactory. 
 From local midnight until about 7:00 AM it was pretty good but once 
people woke up and started using the internet, NTP wasn't working very well.

I'd offer to serve time but my contract with Comcast forbids operating a 
server of any kind!

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