[ntp:questions] long time to report sync per leap indicator, when initial system time is set far into the future

Mike Cook michael.cook at sfr.fr
Tue Dec 12 09:39:22 UTC 2017


> Le 11 déc. 2017 à 12:49, Stephan E. <public-se at innominate.com> a écrit :
> 
> I want ntpd 4.2.8p10 to sync to public servers, then serve time to a local network. It is running with '-g' because initial system time on the host can be far off. I observe that, when initial system time of the host was set > 5 minutes into the future, the time it will take ntpd to report a synced leap second to its clients approaches the time of that initial offset. E.g., when the initial time was erroneously set 24 hours into the future, ntpd will take approximately 24 hours to report a synced time in the LI field to its clients, and they will reject to sync to my host during that period.
> 
> Is this behavior to be expected, or is it likely that am I doing something wrong? I would agree that it is a weird scenario, but it can not be ruled out in my application.
> 

I am pretty sure that this is expected behavior and a configuration error.

I have tried and failed to reproduce this in either 4.2.8p10 or 4.2.8p9 UNLESS there are NOT ENOUGH sufficiently stable servers available at start up.

That is to say, that if their reach values does not tend to 377. 

for example if I have only 2 servers configured and only one is stable such as here:

Tue Dec 12 08:19:11 UTC 2017
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 time-c-g.nist.g .NIST.           1 u    5   16  275   95.193  -398059   0.047
 india.colorado. .NIST.           1 u   14   16  377  130.526  -398062   0.050

The leap indicator  will remain 11, i.e. unsynchronized

Tue Dec 12 08:19:03 UTC 2017
processor="armv7l", system="Linux/3.8.13-bone47", leap=11, stratum=16,
Tue Dec 12 08:19:08 UTC 2017
processor="armv7l", system="Linux/3.8.13-bone47", leap=11, stratum=16,
Tue Dec 12 08:19:13 UTC 2017
processor="armv7l", system="Linux/3.8.13-bone47", leap=11, stratum=16,
Tue Dec 12 08:19:18 UTC 2017

So you should make sure that you select servers that have good connectivity ( closer is better ) and use a minimum of 5.

So to debug this,  change your date , restart ntpd with just -g and then monitor the server status.  If the servers are showing poor connectivity, change/add .

Hope this helps

> A workaround appears to be running with '-g -q' first, in which case ntpd will sync and exit under 1 minute; then run without either option, in which case the LI field will report a sync within approx. 300s.
> 
> Do you think the workaround is suitable, or am I inviting e.g. errors in leap second handling?
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