[mythtv-users] Zotac ION + NTP clock too fast?

[David Brodbeck]

David Brodbeck wrote:
> Matt W wrote:
>> I would go through your ntp.conf file and rip out a lot of the
>> 'cruft'. I still don't understand why so many Linux distros' feel the
>> need to put the LOCAL clock as a peer in the stock config. Rip that
>> out if it's there.
>>
> I think it's because of what happens if you're using that machine as an
> NTP server as well as a client. By putting in a LOCAL clock with a
> really high stratum number, if the machine loses its other peers, its
> overall stratum number goes high and other hosts know not rely on it too
> heavily.

Turns out I was wrong about this, but the real reason is pretty
interesting.  NTP normally maintains a drift file where it stores its
calculated value for the internal clock's drift rate.  It automatically
uses this value to trim the clock to cancel out drift and make it more
accurate -- but it will only trim the clock if it has at least one valid
peer.  So adding a LOCAL entry allows NTP to keep trimming the clock even
if it loses network access for a while, say on a laptop.