Synchronize chrony with a Windows NTP Server

This document (000020824) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP3
SUSE Linux Enterprise Server 15 SP2
SUSE Linux Enterprise Server 15 SP1
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP4
SUSE Linux Enterprise Server 12 SP3
SUSE Linux Enterprise Server 12 SP2
SUSE Linux Enterprise Server 12 SP1

Situation

chronyd is a daemon for synchronization of the system clock. When setting chrony to synchronize with a Windows NTP, for instance and using the default configuration file (/etc/chrony.conf), the server will be displayed as “unusable”. The output is similar to the following:

# /usr/bin/chronyc -n sources
MS Name/IP address         Stratum Poll Reach LastRx Last sample               
===============================================================================
^? 172.16.96.11                  1   6   377    61   -11.4s[ -11.4s] +/-  11.0s

On the above output, the server 172.16.96.11 is marked with ^?:

^ means this is a server
? means this server is currently unusable.

Alternatively, use /usr/bin/chronyc -n sources -v for further details and explanation of each column on the output displayed.

Resolution

Edit the /etc/chrony.conf making sure to add the maxdistance parameter. Example below:

server win-samba.mydomain.com iburst 
driftfile /var/lib/chrony/drift
maxdistance 16.0    # <--- if your NTP is a Windows Server, then use this as starting value. Adapt if necessary.
makestep 1.0 3
rtcsync
keyfile /etc/chrony.keys
leapsectz right/UTC
logdir /var/log/chrony

From the chrony.conf man page:

By default, the maximum root distance is 3 seconds.
Setting maxdistance to a larger value can be useful to allow synchronisation with a server that only has a very infrequent connection to its sources and can accumulate a large dispersion between updates of its clock.

Cause

The default maximum root distance (of 3 seconds) is being used.

Additional Information

Reference:

https://documentation.suse.com/sles/15-SP4/html/SLES-all/cha-ntp.html
https://chrony.tuxfamily.org/doc/4.3/chrony.conf.html#maxdistance

Disclaimer

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