Re: [chrony-users] Measuring system clock quality without setting system clock

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On Thu, Mar 02, 2017 at 08:39:40PM +0000, Trent Piepho wrote:
> Is there a way to get chrony to produce statistics on the clock quality,
> without actually setting the clock?
> I see the -Q option, but that only prints out the offset as a single
> shot.  I'd really like better data, as in what would be reported by
> "tracking".
> Is there some way to do this?  Or some reason why it would not be
> possible?

If you specify all sources with the noselect option, chronyd won't
touch the clock, but the skew and stddev printed by "chronyc
sourcestats" should still be useful.

> In the final end use of the device, it won't be connecting to NTP
> servers and won't be acting as one either.  So I'd rather not install an
> NTP server on it.  It looks like with hardpps in the kernel it should be
> possible to get a good clock without using an application like ntpd or
> chrony.

That could work. You will probably still need a program that would
bring the clock close to the right second and manage the kernel PPS
discipline. Depending on how good is the PPS signal and what are your
requirements on accuracy, it might be acceptable. Note that chronyd
can be compiled without support for NTP, CMDMON and RTC, which should
reduce the size of the chronyd binary by about third.

Miroslav Lichvar

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