[ntp:questions] NTPD silently not tracking

Magnus Danielson magnus at rubidium.dyndns.org
Fri Aug 30 06:07:38 UTC 2013

On 08/30/2013 04:17 AM, E-Mail Sent to this address will be added to the
BlackLists wrote:
> Magnus Danielson wrote:
>> We had another incident where a node configured with multiple NTP
>> sources had an NTPD which when asked with ntpdc have peers, looks like
>> things are all OK, but with offsets less than a second, while the node
>> in fact was 6 days off the mark. Only on a number of ntpdc querries did
>> some of the peers expose a gigantic offset. Everything looked OK, but
>> time was off such that normal remote login did not work.
>> The error was way to non-obvious and felt like a Heisenbug in that only
>> when we looked more carefully at it, it started to see itself that it
>> was out of touch with reality.
>> ii  ntp   1:4.2.6.p5+d i386   Network Time Protocol daemon and
> What ntpdc commands did you issue, and what results did you get?
> Did you also try ntpq commands, did you see differing results?
> ntpq -n -c "rv 0 leap"
> ntpq -n -c "rv 0 stratum"
> ntpq -n -c "rv 0 refid"
> ntpq -n -c "rv 0 offset"
> ntpq -n -c "rv 0 rootdisp"
Unfortunatly no. I got the call after the fact, but lack of remote login
due to time error would prohibit  me from doing anything anyway. The
server needed to be operational rather than optimize for NTP debugging.
> Have you tried a newer version of NTP ?
> <http://www.ntp.org/downloads.html>
> <http://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-dev/>
> <http://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-dev/ntp-dev-4.2.7p385.tar.gz>
No, I listed the affected version as packaged by Debian.
> Don't use Undisciplined Local Clock
>  Try Orphan instead is you need LAN NTP clients to stick together
>   while LAN and/or Internet NTP servers become unavailable.
>  ...
>  keys "/etc/ntp.keys" # e.g. contains: 123 M LAN_MD5_KEY , 321 M Corp_MD5_KEY , ...
>  trustedkey 123 321
>  tos cohort 1 orphan 10
>  restrict source nomodify
>  manycastserver
>  manycastclient key 123 preempt
>  ...
It has 2 stratum 1 and 3 stratum 2 unicast servers configured. NTP wise
this machine is a client with 5 configured servers. The problem was that
it was way off time with no apparent indication, which is wrong.


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