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

[Henrik Bieler <henrik.bieler@xxxxxx>]

Hey,

The problem seems indeed to be coming from the gpsd u-blox driver.
If I disable the automatic detection (gpsd -b .... ) gpsd uses the
legacy NMEA driver instead of the u-blox-driver and there is no wrong
time supplied.

I still would like to know a way of preferring the ntpd over the gps
when they are online. And switching back to gps when they go offline.

Maybe someone can explain how chrony selects sources or point to
documentation.

Thank you :-)




Am 10.03.2016 um 19:30 schrieb Olivier Delbeke:
> Hi Henrik,
> 
> On Thu, Mar 10, 2016 at 7:11 PM, Henrik Bieler <henrik.bieler@xxxxxx
> <mailto: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
> 
>     --
>     To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
>     <mailto:chrony-users-request@xxxxxxxxxxxxxxxxxxxx>
>     with "unsubscribe" in the subject.
>     For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
>     <mailto:chrony-users-request@xxxxxxxxxxxxxxxxxxxx>
>     with "help" in the subject.
>     Trouble?  Email listmaster@xxxxxxxxxxxxxxxxxxxx
>     <mailto:listmaster@xxxxxxxxxxxxxxxxxxxx>.
> 
> 
> 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


-- 
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx 
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx 
with "help" in the subject.
Trouble?  Email listmaster@xxxxxxxxxxxxxxxxxxxx.