Score:0

Is chronyc preventing big jumps by itself?

ca flag

I just realized that Windows server time (w32t service) has two default values limiting how much the offset of the time is allowed to be in negative and positive values. This value is huge by default and this allows for big time jumps if you dont correct the necessary regedit values.

On Ubuntu Server, I use chronyc for time sync. Is chronyc allowing this same fatal error or does it only allow smaller steps? I can provide any configurations if needed, just dont know what to provide.

Thanks!

Status print from one of our servers:

xxxxxxxxxxx:~$ chronyc tracking
Reference ID    : D9C6DB66 (n1.taur.dk)
Stratum         : 2
Ref time (UTC)  : Fri Apr 21 20:15:09 2023
System time     : 0.000020651 seconds fast of NTP time
Last offset     : +0.000022519 seconds
RMS offset      : 0.000074701 seconds
Frequency       : 5.647 ppm slow
Residual freq   : +0.000 ppm
Skew            : 0.005 ppm
Root delay      : 0.001985608 seconds
Root dispersion : 0.000785804 seconds
Update interval : 1034.6 seconds
Leap status     : Normal

UPDATE:

https://chrony.tuxfamily.org/doc/3.4/chrony.conf.html

From this documentation, it looks like maxslewrate is the value that defines how much the clock is allowed to jump. Is that correct?

Score:0
ca flag

I think I can conclude that as default, chronyc wont suffer from big jumps as is the case with default behaviour of the w32t service.

https://chrony.tuxfamily.org/doc/3.1/chronyc.html

"In normal operation, chronyd by default never steps the system clock, because any jump in the time can have adverse consequences for certain application programs. Instead, any error in the system clock is corrected by slightly speeding up or slowing down the system clock until the error has been removed [...]"

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