Re: [chrony-users] Chrony source selection algorithm documentation

Hi Henrik,

On Thu, Mar 10, 2016 at 7:11 PM, Henrik Bieler <henrik.bieler@xxxxxx> wrote:

Am 10.03.2016 um 18:27 schrieb Olivier Delbeke:
> Hi Henrik,
>

> I'm just a chrony user, but I would say that, in your case, you should
> address the root cause of the problem :
>>> Sometimes when the GPS has no fix the GPS-Time received by chrony
> through SHM is off by several years.
>
> GPS-sensors normally do not behave like that. They either don't provide
> a time, or provide a correct one. You should probably fix the software
> that provides that erroneous GPS time (if possible).
>
> Best regards,
>
> Olivier
>
>

I agree. However I would strongly prefer sticking with packages in the
standard repository.
When I display the GPS in "no fix state" using gpsmon. There is no time
indicated. This seems correct.
However chrony reads a grossly incorrect date from shared memory. That
might be a bug in gpsd or chrony. So fixing it would probably involve
compiling or using non-repository packages of some sort.
If I can work around this issue by configuring chrony in the way
described in my previous mail, that would be my first choice.

Cheers Henrik

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Combining gpsd and chronyd is indeed far from being exotic and should work just fine. With some luck, you will be able to work-around the problem with proper configuration files for chrony or gpsd, but you might also have stumbled onto an already fixed bug (and in that case, you could fix it by using a more recent version of the existing packages). I just downloaded chrony's source code (tag 1.30) and saw that there is a "valid" flag in the data structure passed on the SHM ; and it seems to be handled correctly by chrony. If I were you, I would look in the direction of gpsd (source code, config file, change history, try new version or mailing list).

Best regards,

Olivier