[ntp:questions] ntpdate works, but ntpd doesn't (reach = 0)

Martin Burnicki martin.burnicki at meinberg.de
Mon Feb 16 11:22:00 UTC 2009

Danny Mayer wrote:
> Martin Burnicki wrote:
>> Unruh wrote:
>>> Harlan Stenn <stenn at ntp.org> writes:
>>>>>>> In article <ST4ll.11327$Db2.8064 at edtnps83>, Unruh
>>>>>>> <unruh-spam at physics.ubc.ca> writes:
>>>> Unruh> Why is -g inappropriate from a resttart. If the clock is still
>>>> very Unruh> close to right, it will make no difference. If for some
>>>> reason on Unruh> restart the clock is out, then -g is appropriate. Ie,
>>>> I cannot see Unruh> why it would hinder anything if it were run on
>>>> restart. I'm getting tired of repeating myself.
>>> Repeating yourself is different from explaining yourself. You feel that
>>> ntpd should have "not -g" as the default. A number of us suggest that -g
>>> is a more appropriate default (ie so that to stop ntp from doing a time
>>> reset once would then require some flag).
>>> You say I can rewrite ntpd, or set up a special ntp.conf file or...
>>> But I still do not understand why -g should not be the default.
>> Again, I absolutely agree to the above.
>> I don't see any restrictions in cases where ntpd is re-(!)started with -g
>> even though this case is obviously which prevents -g from becoming the
>> default.
>> I'd just like to know a condition where -g is Bad in the particular case
>> of restarting ntpd.
> There are a couple of situations where a step rather than a slew would
> be really bad on a restart of ntp (as opposed to a reboot of the O/S).
> One of these cases is with databases timestamping a transaction where a
> step backward would result in a transaction taking place before some
> other transaction. These are real financial issues that are involved.
> Note that on a regular startup, ntpd should be started before the
> database so that the issue is not a problem. A restart *after* things
> are running becomes a real big problem. Another instance is in a lab
> network where time is extremely important. In addition I hear in TICTOC
> that there may be problems with different segments that they are trying
> to deal with.

However, from the discussion here it seems that only restarting ntpd with -g
is bad, without -g does not seem to be Bad, even though it may result in a
time step back up to the 1000 s sanity limit ...

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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