RE: [chrony-dev] makestep command sometimes makes chrony stop reading its sources

["Hattink, Tjalling (FINT)" <T.Hattink@xxxxxxxx>]

> From: Bill Unruh
> Sent: Wednesday, January 20, 2010 16:11
> 
> On Wed, 20 Jan 2010, Hattink, Tjalling (FINT) wrote:
> 
> >
> > The tricky part ofcourse is handling the situations where the GPS
time 
> > is not synchronised or when the RTC is way off. So far I've found
two 
> > issues with Chrony regarding these border cases. In this mail I'll 
> > describe my first issue. The second one will be in the next mail to 
> > properly separate the discussion of both issues.
> >
> > What I'm testing is how chrony recovers when the RTC is way off
during 
> > boot. In the bios I adjust the RTC clock with one year. Because
Chrony 
> > is only slewing the clock it would take ages to recover from this 
> > situation, so I made a script that checks if the offset is too large
> 
> chrony already handles this, with the configuration command
initstepslew
> 30 124.45.6.7 means when chrony starts up, it sends a number of ntp
> packets to the location 123.45.6.7 and it steps the clock to put the
> chrony time into sync with that clock if chrony finds that the system
> clock ( after being set with rtc) is out by more than 30 sec.
> 
>   You can adjust that 30 to anything you want.
> 
> So no need for you to make your own script.
> 

I've looked into the initstepslew command but I think it only works for
NTP
sources, and I only have a reference clock available (SHM, PPS). Also
the
reference clock is not immediately available after chronyd is started.
It
takes a minute before the SHM interface starts providing time samples,
as
GPS needs to lock in. It can even take much longer, for example when the
GPS antenna is not connected during start-up, but is attached an hour
later. So even if initstepslew is able to handle reference clocks I'm
not
sure if it will work when the reference clock is not immediately
available.

Best regards,

Tjalling Hattink

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