| Re: [chrony-users] Chrony 3.1 refuses to sync with ntp server |
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On Tue, Nov 28, 2017 at 06:10:29PM +0000, Assaf Vainsencher wrote:
> We recently updated from RHEL 7.3 to RHEL 7.4 which updated chrony to version 3.1 and we can't get it to sync properly with NTP server running on windows server 2008R2 - chronyc sources reports ^? Status for any of the windows 2008 NTP servers we try. Version 2.1.1 in RHEL 7.3 syncs fine. One of our software engineers tried compiling and installing version chrony 3.2 and it still didn't work. Downgrading chrony fixes the issue. Is there a suggested fix for this that we can try with our chrony configuration or is this a known incompatibility issue?
>
> We also found this post on stackexchange with someone experiencing a similar, if not the same, issue:
>
> https://unix.stackexchange.com/questions/404046/chrony-3-1-refuses-to-sync-with-ntp-server
The debug output attached there shows that the NTP server has a root
dispersion which is too large to pass the source selection in the
default configuration. As I understand it, this is a common issue with
the Windows NTP server if it uses a long polling interval. If you run
"chronyc ntpdata", it should print the value from the last response.
There is a hardcoded limit of 16 seconds for the root distance, which
includes the root dispersion, but since chrony-2.2 there is an
additional requirement applied in the source selection. By default it
is 3 seconds. If your server has a larger dispersion (and distance),
you will need to increase the maximum distance with "maxdistance XX"
in chrony.conf.
--
Miroslav Lichvar
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