[ntp:questions] ntpd and database servers

unruh unruh at wormhole.physics.ubc.ca
Fri Jan 15 16:30:33 UTC 2010

On 2010-01-15, David Woolley <david at ex.djwhome.demon.invalid> wrote:
> unruh wrote:
>> Note, chrony, another implimentation of ntp, can adjust the clock much
> Although I tend to agree that for most users chrony may behave better 
> than ntpd, it is a user of the NTP wire formats, but not an 
> implementation of NTP. Obeying the slew rate limit is necessary before 
> you can claim to implement NTP, rather than SNTP.

Sorry, I do not buy that. The reference implimentation does not honour
that limit. It will step the clock, which is an infinite slew rate. And
as David Mills himself has said, that 500PPM was a figure hauled off the
top of his head-- there is not particular justification for it. 
The advice is that you adjust your computer's c;lock by hand using the
tick adjust so that it
is withing 500PPM and then use ntp. All chrony does is to automate that
procedure and adjust the tick to bring the system time within 500PPM.
So, let me phrase it this way. Chrony impliments the ntp. It also has a
mechanism to automatically adjust the system clock tick size to bring it
within the ntp 500PPM limit. Does that make you happier?

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