Re: [chrony-users] PTP TAI Query

[Chris Hodgetts <chris@xxxxxxxxxxxxxxxx>]

Hello,

Just a quick follow-up in case anyone else runs into this.

I was initially seeing all zeros and a “?” on the PHC source line, which made it look like chrony wasn’t treating the PHC as a valid source, but there were no errors when iit started, or that I could see in any log. 

I originally suspected a chrony issue after upgrading, but it turned out not to be related to chrony at all.

The actual cause was that right/UTC was no longer present in my tzdata after upgrading to Debian 13 (at least on my system). 

Without that file, the TAI offset couldn’t be read correctly. Removing the TAI directive resulted in a 37-second offset, and enabling it again produced no usable time source.

Once I restored the correct tzdata files, everything returned to normal.

Reference ID    : 50484330 (PHC0)

Stratum         : 1

Ref time (UTC)  : Mon Nov 24 12:32:38 2025

System time     : 0.000000001 seconds fast of NTP time

Last offset     : +0.000000003 seconds

RMS offset      : 0.000000016 seconds

Frequency       : 13.669 ppm slow

Residual freq   : +0.000 ppm

Skew            : 0.005 ppm

Root delay      : 0.000000001 seconds

Root dispersion : 0.000000911 seconds

Update interval : 1.0 seconds

Leap status     : Normal

MS Name/IP address         Stratum Poll Reach LastRx Last sample               

===============================================================================

#* PHC0                          0   0   377     0    +55ns[  +59ns] +/-   38ns

^- time-a-g.nist.gov             1  10   377   117    -35ms[  -35ms] +/-  140m

That NIST will go away shortly - it was there to attempt to work out what was going on with my PHC and work out if it was actually working or not. 

On 24 Nov 2025, at 21:39, Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:

On Sun, Nov 23, 2025 at 09:23:05PM +1300, Chris Hodgetts wrote:

Hello,

I have just upgraded to chrony version 4.6.1 on Debian 13

I have noticed my PTP time has not failed, and it appears to be when I put :

refclock PHC /dev/ptp0 poll 0 dpoll 0 tai

If I remove tai - I get 37 second offset and Chrony does not sync to PTP.

What exactly failed means here? Not being selected for
synchronization? Please provide output from the chronyc sources
command.

How is the PHC synchronized? Is it ptp4l?

--
Miroslav Lichvar