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I have a server where a lot of time chronyd isn't able to sync the system clock leading at a situation like that :

Reference ID    : 0A263C14 (10.38.60.20)
Stratum         : 4
Ref time (UTC)  : Tue Jun 04 12:20:09 2019
System time     : 4576.955566406 seconds fast of NTP time
Last offset     : +0.000107134 seconds
RMS offset      : 1.026136756 seconds
Frequency       : 80.575 ppm slow
Residual freq   : -0.003 ppm
Skew            : 0.019 ppm
Root delay      : 0.024930937 seconds
Root dispersion : 0.071089722 seconds
Update interval : 1030.2 seconds
Leap status     : Normal

If a issue a command like chronyc makestep which force the synchronization the system time went back to normal but after one days or two i have the same problem, the only thing which i have noticed is that the "last sample" from chronyc sources is very high :

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^? 10.37.23.20                   0   6     0     -     +0ns[   +0ns] +/-    0ns
^? 10.13.186.21                  0   6     0     -     +0ns[   +0ns] +/-    0ns
^* 10.38.60.20                   3  10   377   222  -4128us[-3993us] +/-  105ms
^? 10.15.214.60                  0   6     0     -     +0ns[   +0ns] +/-    0ns
^? 10.29.147.252                 0   6     0     -     +0ns[   +0ns] +/-    0ns
^? 10.25.100.172                 0   6     0     -     +0ns[   +0ns] +/-    0ns
^? 10.32.117.205                 0   6     0     -     +0ns[   +0ns] +/-    0ns
^? 10.32.62.252                  0   6     0     -     +0ns[   +0ns] +/-    0ns
^? 10.38.156.92                  0   6     0     -     +0ns[   +0ns] +/-    0ns
^+ 10.25.144.92                  4  10   377   242  -4371us[-4235us] +/-  121ms
^+ 10.38.27.76                   4  10   265   568  -4863us[-4724us] +/-

Any clue about what could be ? The server is a vmware virtual machine.

Thanks, Tommaso.

1

Before makestep, you were +4576 seconds offset from 10.38.60.20. After, you are -0.003993 seconds. Microseconds unit is important, that's 6 decimal places difference.

Estimated error in the last column is +/- 0.105 seconds. That is on the high end of what I expect from a LAN, because it only takes about 0.200 s latency on many paths to the other side of Earth.

Improve on this by making more, low latency NTP servers reachable; none should be reach 0. Confirm each is a NTP server. Remove any firewall rules unnecessarily blocking you from accessing NTP servers.


Regarding hypervisors, be sure the host clock is synced to the same NTP service as everything else.

  • Hi, thanks for your explanation hovewer i didn't do any makestep yet the value of -3993us is taken when the clock is out of sync of 4576s what i can't undestand is why chronyd isn't able to correct the system clock automatically as should be, this happen only with these virtual machine. Best regards Tommaso. – thomas Jun 5 at 6:33
  • Then fix the VM host's NTP, plus on the guest stop any services that don't like being stepped and run makestep. Do so before some event happens that forces a guest time sync, like a guest snapshot. Depends on the makestep directive in chrony.conf, but usually step is not allowed after chronyd is started. – John Mahowald Jun 5 at 9:57

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