[ntp:questions] PSYCHO PC clock is advancing at 2 HR per second

unruh unruh at invalid.ca
Tue Mar 20 23:36:23 UTC 2012

On 2012-03-20, David Lord <snews at lordynet.org> wrote:
> Ron Frazier (NTP) wrote:
>> Hi David L,
>> See below.
>> On 3/20/2012 1:00 PM, David Lord wrote:
>>> Ron Frazier (NTP) wrote:
> ....
>>>> Hi David T,
>>>> Eventually, I do plan to have the server preferences as follows:
>>>> Time server machine:
>>>>    GPS
>>>>    Internet as backup
>>>> Hypothetically speaking, what if I don't want it to distribute time 
>>>> if it's working in internet mode?
>>> Easy, configure it that way.
>> I'm not sure how to do that within the confines of ntp.conf.  David T. 
>> suggested I could run a Perl script every minute to shut down NTP if the 
>> GPS fails.  But, I'd rather keep NTP running and just not distribute 
>> time on the LAN when my time server is polling the internet.  Which 
>> brings up a question.  If my time server on my LAN is attached to the 
>> GPS, that GPS is considered stratum zero and my time server on the LAN 
>> appears to be a stratum 1 device to other computers, right?  Then, what 
>> if the time server stops using the GPS and begins using internet stratum 
>> 2 servers as it's time source?  Does my LAN time server now present 
>> itself as a stratum 3 device to the other PC's on the LAN?  If so, they 
>> might automatically stop using it and poll the internet stratum 2 
>> servers themselves.  That would be fine.
> "ntpd" is not designed to be restarted often, either by
> scripts or by reboot to another operating system. If that
> is your requirement use ntpdate to get you perhaps within
> a second.
> Ntp.conf provides options to limit responses from ntpd.
> That begs the question, was your ntpd answering requests
> when your server was 50 seconds out?

Since all it has was LOCL as a time source, there is no reason why it
shouldn't answer requests. For all it knew it was exactly on time.
Every time it measured the offset, the offset was 0. That is pretty good
timekeeping! :-)

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