Re: [chrony-users] How to avoid oversteering

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chronyd should not be doing that. It has a very efficient way of determining
what the correct rate should be, and uses an extra drift to drive the offset
to zero.


Is this on real hardware on a virtual machine? Chrony should not be run on
virtual machines, because the timing on those is a mess. Their internal clocks
are not regular.

Alternatively it could be a severe hardware issue, or you could be running the
system on a tickless clock.


On Mon, 5 Feb 2018, Ariel Garcia wrote:

Hello,

i am trying to get Chrony 3.2 running without stepping the clock, but i
find that it oversteers by a huge amount.  I observe that it starts driving
the system clock to the right value, but then moves it more that the
initial offset in the opposite direction, and starts "oscillating".

I rebooted to make sure the system clock runs at the "default" speed
initially, having previously set the RTC ~10s off from the correct time
for testing. After chrony started it reported:
    System time     : 10.891304016 seconds slow of NTP time
After ~ 10 minutes running it was already:
    System time     : 2.529696226 seconds slow of NTP time
but then after ~20 minutes  it was already in the opposite direction:
    System time     : 12.160170555 seconds fast of NTP time
After one hour running it is worse than at the beginning:
   System time     : 16.009445190 seconds slow of NTP time


What am i doing wrong, am i having the wrong expectation, or could
it be a hardware or a configuration issue?
(the drift  values shown above are consistent with the device's RTC
--which is not being adjusted-- and an external PC)

I've tried to collect all details below,
thanks in advance for any hints/help!!
Ariel


================================================================
Running on a BeagleBone black-similar board, with an AM335X CPU.

My configuration was chosen as simple as possible to start:
--------------------------------
pool de.pool.ntp.org   minpoll 4
makestep 3600 3
logchange 0.05
cmdallow 127.0.0.1
bindcmdaddress /run/chrony/chronyd.sock
pidfile /run/chrony/chronyd.pid
-------------------------------

Of course i made sure there is no other NTP daemon running.
These are all running processes (only deleted my open ssh connections)
--------------------------------
   1 ?        Ss     0:10 /sbin/init
 978 ?        Ss     0:03 /usr/sbin/rngd -f
 985 ?        Ss     0:04 /lib/systemd/systemd-journald
1773 ?        Ss     0:00 /lib/systemd/systemd-udevd
1805 ttyO0    Ss+    0:00 /sbin/agetty --keep-baud 115200 38400 9600 ttyO0 vt220
1812 ?        Ss     0:00 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
1813 ?        Ss     0:00 /usr/sbin/crond -b
1827 ?        Ss     0:00 /lib/systemd/systemd-networkd
1834 ?        Ss     0:00 /lib/systemd/systemd-resolved
15344 ?        S      0:00 /usr/sbin/chronyd -4 -f /etc/chrony/chrony.conf
--------------------------------

The servers are reachable and seem ok:
--------------------------------
$ chronyc -n sources
210 Number of sources = 4
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^- 172.104.239.150               2   4   377     3  -1158ms[-1158ms] +/-   58ms
^- 138.201.135.108               2   4   377     4  -1057ms[-1057ms] +/-   47ms
^* 195.34.187.132                2   4   377    14    +17ms[-1527ms] +/-   28ms
^- 5.9.78.71                     2   4   377    13   -142ms[ -142ms] +/-   50ms

$ chronyc -n sourcestats
210 Number of sources = 4
Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
==============================================================================
172.104.239.150             6   3    75    -103422   1668.695  -1033ms    14ms
138.201.135.108             6   3    75    -103305   1165.815  -1020ms    11ms
195.34.187.132              6   3    75    -103052   2391.831  -1021ms    15ms
5.9.78.71                   6   3    75    -102973   2085.425  -1017ms    14ms
--------------------------------

The logs show
---------------------------------
Feb 05 17:18:22 BBx systemd[1]: Starting NTP client/server...
Feb 05 17:18:22 BBx chronyd[15344]: chronyd version 3.2 starting (+CMDMON +NTP +REFCLOCK +RTC +PRIVDROP -SCFILTER -SECHASH -SIGND +ASYNCDNS +IPV6 -DEBUG)
Feb 05 17:18:22 BBx chronyd[15344]: Initial frequency 42.124 ppm
Feb 05 17:18:22 BBx systemd[1]: Started NTP client/server.
Feb 05 17:18:55 BBx chronyd[15344]: Selected source 129.70.132.35
Feb 05 17:18:56 BBx chronyd[15344]: System clock wrong by 11.087803 seconds, adjustment started
Feb 05 17:19:11 BBx chronyd[15344]: Can't synchronise: no majority
Feb 05 17:19:12 BBx chronyd[15344]: Selected source 129.70.132.35
Feb 05 17:19:12 BBx chronyd[15344]: System clock wrong by 1.096591 seconds, adjustment started
Feb 05 17:19:27 BBx chronyd[15344]: Selected source 138.201.135.108
Feb 05 17:19:27 BBx chronyd[15344]: System clock wrong by 0.943644 seconds, adjustment started
Feb 05 17:19:43 BBx chronyd[15344]: System clock wrong by 1.241887 seconds, adjustment started
...
(lots or similar lines, but always the system clock is reported to be wrong
 by +2 to -2 seconds, never by the amount shown by "chronyc tracking")
...
---------------------------------

The tracking data at different times:
---------------------------------
$ chronyc tracking
Reference ID    : 81468423 (stratum2-2.NTP.TechFak.NET)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 17:19:05 2018
System time     : 10.891304016 seconds slow of NTP time
Last offset     : -11.087802887 seconds
RMS offset      : 11.087802887 seconds
Frequency       : 42.124 ppm fast
Residual freq   : +1.113 ppm
Skew            : 1000000.000 ppm
Root delay      : 0.037714522 seconds
Root dispersion : 3.768865824 seconds
Update interval : 0.0 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : 8AC9876C (srv23.globale-gruppe.com)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 17:19:37 2018
System time     : 9.804729462 seconds slow of NTP time
Last offset     : -0.943643808 seconds
RMS offset      : 0.943643808 seconds
Frequency       : 42.124 ppm fast
Residual freq   : -41046.902 ppm
Skew            : 1000000.000 ppm
Root delay      : 0.033498995 seconds
Root dispersion : 12.330061913 seconds
Update interval : 14.3 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : 81468423 (stratum2-2.NTP.TechFak.NET)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 17:24:13 2018
System time     : 9.454131126 seconds slow of NTP time
Last offset     : +0.030433958 seconds
RMS offset      : 0.640062451 seconds
Frequency       : 90705.453 ppm slow
Residual freq   : +86.611 ppm
Skew            : 1054.889 ppm
Root delay      : 0.035278354 seconds
Root dispersion : 0.017751774 seconds
Update interval : 16.1 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : 81468423 (stratum2-2.NTP.TechFak.NET)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 17:31:07 2018
System time     : 2.529696226 seconds slow of NTP time
Last offset     : +0.029113885 seconds
RMS offset      : 0.166937038 seconds
Frequency       : 77410.445 ppm slow
Residual freq   : +1074.334 ppm
Skew            : 1991.644 ppm
Root delay      : 0.035502460 seconds
Root dispersion : 0.027657172 seconds
Update interval : 15.8 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : 8AC9876C (srv23.globale-gruppe.com)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 17:37:24 2018
System time     : 6.902931690 seconds fast of NTP time
Last offset     : +0.189766780 seconds
RMS offset      : 1.233845592 seconds
Frequency       : 108520.094 ppm fast
Residual freq   : +12504.339 ppm
Skew            : 30318.885 ppm
Root delay      : 0.034667145 seconds
Root dispersion : 0.311530590 seconds
Update interval : 16.1 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : 81468423 (stratum2-2.NTP.TechFak.NET)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 17:45:10 2018
System time     : 13.315183640 seconds fast of NTP time
Last offset     : -0.028802348 seconds
RMS offset      : 0.300014675 seconds
Frequency       : 106800.570 ppm fast
Residual freq   : -74.106 ppm
Skew            : 1022.886 ppm
Root delay      : 0.034821544 seconds
Root dispersion : 0.017649684 seconds
Update interval : 16.2 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : C322BB84 (powered.by.inet.de)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 18:06:29 2018
System time     : 4.486146450 seconds slow of NTP time
Last offset     : -0.437962651 seconds
RMS offset      : 1.165199637 seconds
Frequency       : 19659.746 ppm slow
Residual freq   : -14884.478 ppm
Skew            : 39623.336 ppm
Root delay      : 0.025750067 seconds
Root dispersion : 0.237240255 seconds
Update interval : 3.7 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : C322BB84 (powered.by.inet.de)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 18:19:55 2018
System time     : 16.009445190 seconds slow of NTP time
Last offset     : +0.026499212 seconds
RMS offset      : 0.694284379 seconds
Frequency       : 102772.656 ppm slow
Residual freq   : +110.795 ppm
Skew            : 1070.995 ppm
Root delay      : 0.027395297 seconds
Root dispersion : 0.030097129 seconds
Update interval : 16.3 seconds
Leap status     : Normal
---------------------------------
$ chronyc tracking
Reference ID    : AC68EF96 (watch.no-such-agency.net)
Stratum         : 3
Ref time (UTC)  : Mon Feb 05 18:52:14 2018
System time     : 17.909534454 seconds fast of NTP time
Last offset     : -0.021534055 seconds
RMS offset      : 0.502140403 seconds
Frequency       : 106267.859 ppm fast
Residual freq   : -85.290 ppm
Skew            : 1018.805 ppm
Root delay      : 0.025392590 seconds
Root dispersion : 0.026234277 seconds
Update interval : 13.1 seconds
Leap status     : Normal
---------------------------------


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