[ntp:questions] NTP 4.2.8p10 released

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Tue May 9 16:04:02 UTC 2017

On 2017-05-09 01:45, ashu6486 at gmail.com wrote:
> How can we add redundant server into NTP 4.2.8p10 ? If we try to
> edit the configuration file it's not switching to the redundant
> server?

After changing the /etc/ntp.conf file, you need to restart any 
server ntp daemon using it to put changes into effect.
When dealing with ntp, patience is often required, to see if 
changes have any obvious effect.

If you have insufficient truechimer sources (3, 5, ...) to form 
a *majority* clique, the time will not be updated, as if you had 
no sources. 

The ntpd daemon looks at the time provided by all upstream sources 
using its algorithms and calculates the correctness interval of the 
majority clique survivors using averages weighted by the normalised 
reciprocal root distance to give the smallest maximum error in both 
offset and jitter. 

If the survivor source with the smallest root distance (and thus 
smallest maximum error), the candidate source, is not the same as 
the previous system source and the offset difference between the 
candidate source and the previous system source is less than the 
clockhop threshold (initially 1ms), the system source stays the 
same and the clockhop threshold is halved, so it could take more 
than one poll interval to replace the system source if offsets 
are very similar. 

These values are updated every time another packet is received 
from any upstream source and passes sanity checks, or the system 
source is unreachable after eight poll intervals. This could take  
128s (~2min) for LAN sources with minpoll 4, or 512s (~8min) for 
network sources with minpoll 6; except at startup with sources 
using iburst, when six packets are sent at poll 1 (2s intervals), 
or after operating for a long period, with network sources at 
default maxpoll 10/1024s, when it could take ~136min to become 

For more details see: 
and linked/related pages.

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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