| Re: [chrony-users] How to read the RTC value? |
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- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] How to read the RTC value?
- From: Jan Claußen <jan.claussen10@xxxxxx>
- Date: Sat, 10 Aug 2024 10:20:06 +0200
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Thank you for the extended explanation again! I don’t view the RTC as a correct source. I was just playing around with very wrong RTC values and wanted to verify if chrony corrects them. I mean you can always do this with timedatectl after disabling chronyd, but it is just tedious. Anyway, not so important I guess.
> Am 09.08.2024 um 21:36 schrieb Bill Unruh <unruh@xxxxxxxxxxxxxx>:
>
> The rtc works correctly if it counts out its own seconds. It's seconds need
> not be the same as UTC seconds for it to work although they should not be too
> far off. It is not supposed to an accurate source of UTC time. Just good
> enough to start of nptd or chrony with roughly ( within a few hours) the
> correct UTC time. After that you use either a good clock (atomic clock, GPS
> time,..) or an internet ntp server to get the time reallywall ( to msec or
> microseconds which an RTC cannot do and was never designed to do) For nsec
> accuracy you need to put in much more work and money, and it is easy to get
> wrong (see the brouha about 10 years ago when neutrinos were measured to go
> faster than light. It turned out to be clock problem at nsec accuracy, not a neutrino problem.
> And that was a multi million dollar experiment, with some really very bright
> people running it. It turned out to be a bad fibre optics connection between
> the gps receiver and the experiment, which delayed the time signal by a nsec
> or so). nsec are hard. microseconds are cheap (<$100) and easy (even I can do
> it).
>
> William G. Unruh __| Canadian Institute for|____ Tel: +1(604)822-3273
> Physics&Astronomy _|___ Advanced Research _|____ Fax: +1(604)822-5324
> UBC, Vancouver,BC _|_ Program in Cosmology |____ unruh@xxxxxxxxxxxxxx
> Canada V6T 1Z1 ____|____ and Gravity ______|_ theory.physics.ubc.ca/
>
>> On Fri, 9 Aug 2024, Jan Claußen wrote:
>>
>> [CAUTION: Non-UBC Email]Well, it is simple. I want to compare if the RTC syncing was successfull and compare
>> the times like I can with timedatectl. This way you can visibly verify that the RTC works correctly. I don't
>> want to calculate anything for this.
>> It is just one line more to add to the rtcdata command. I really don't understand why this was never
>> implemented.
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