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

Danny Mayer mayer at ntp.org
Sun Feb 15 18:31:32 UTC 2009

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.


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