[ntp:questions] Red Hat vote for chrony

Charles Swiger cswiger at mac.com
Sat Dec 6 12:50:46 UTC 2014


> On Dec 5, 2014, at 8:39 PM, William Unruh <unruh at invalid.ca> wrote:
> 
>>>> This is obviously false.  What do you think /etc/ntp.drift is?
>>> 
>>> It is the offset from the standard rate of the clock. That memory is
>>> never used except on bootup. ntpd has to know how much to alter the
>>> drift.
>> 
>> Ah, so you acknowledge that your original statement was wrong.
> 

That wasn't intended to be a trick question.

Hmm.  Unless one considers intellectual honesty to be tricky, perhaps....


>> Just like your claim whether the chrony docs recommend using maxpoll=4
>> across the network to a LAN timesource or not was wrong?
> 
> I have given you the quotes from the chrony docs. Where do you get your
> statement from?

The chrony docs, section 5.3.4:

http://chrony.tuxfamily.org/manual.html#How-can-I-improve-the-accuracy-of-the-system-clock-with-NTP-sources_003f

>> Just like your claim about whether ntpd cares about figuring out the local
>> clock frequency or whether it only chases the offset was wrong?
> 
> ntpd does not care about figuring out the local clock frequency.

You keep repeating this assertion when it is quite obviously wrong.

Above, you've acknowledged that ntp.drift contains the (frequency) offset
for the clock.  That's the single most important piece of data to have
around even if the machine loses network connectivity with other timeservers,
or ntpd is restarted, or the machine itself is rebooted.

Figuring out the local clock frequency is the most important thing
ntpd does.  Getting that right means that the local clock can be trusted
to provide reasonably accurate time for a decent while even if freewheeling.

(Or for the folks who don't care whether their noon is a minute off from
real time, just so long as everything on the LAN in their isolated island
is mutually synced and that there are 3600 computer seconds per hour of
wall clock time.)

Regards,
-- 
-Chuck


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