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.
  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 Delarich
Product Manager
LOYTEC electronics GmbH

To unsubscribe email chrony-users-requ...@chrony.tuxfamily.org
with "unsubscribe" in the subject.
For help email chrony-users-requ...@chrony.tuxfamily.org
with "help" in the subject.
Trouble?  Email listmas...@chrony.tuxfamily.org.

Reply via email to