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- Subject: [chrony-users] Can't synchronise: no majority
- From: Niko Delarich <ndelarich@xxxxxxxxxx>
- Date: Wed, 25 Mar 2020 13:22:11 +0000
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- Thread-topic: Can't synchronise: no majority
Hi,
we use chrony 3.5 in an embedded network device (Linux 4.4.122 armv7l).
In some of our customers installations we've noticed that chrony is sometimes unable to synchronize correctly if the two configured NTP servers don't agree on a time (i.e. the source intervals don't overlap).
In one specific case the customer has two NTP servers:
#1: Windows Server 2012 R2 NTP Server (Stratum 14) running in a VM (yes, I know - probably not a good idea)
#2: Cisco router with NTP server (Stratum 3)
chronyc sources:
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^x <server 1> 14 7 377 90 +1518us[+1518us] +/- 23ms
^x <server 2> 3 10 377 248 -248ms[ -248ms] +/- 66ms
chronyc sourcestats:
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
==============================================================================
<server1> 13 7 25m +0.090 1.386 +2099us 543us
<server2> 7 5 102m -41.170 0.662 -258ms 371us
After comparing the source intervals, the "Can't synchronise: no majority" message is emitted if the two servers don't agree on a time.
sources.c:907
Could not even get half the reachable sources to agree and there are no trusted sources - clearly we can't synchronise
I know the situation is not ideal and the customer should probably just use better servers but shouldn't chrony just pick the "better" of the two servers in this case (#2 with stratum 3)?
There's a comment in sources.c:869 which seems to indicate it should:
The first case is just bad luck - we need extra sources to
detect the falseticker, so just make an arbitrary choice based
on stratum & stability etc.
Or is there maybe a configuration option I'm missing? Setting one of the sources to "trusted" manually is most likely not an option for us since the servers may be assigned by a DHCP server.
Thanks for your help,
Niko
------------
Niko Delarich
Product Manager
LOYTEC electronics GmbH
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