[ntp:questions] what happens if ntp server jumps time BIG TIME

unruh unruh at invalid.ca
Sat Feb 11 19:02:43 UTC 2012

On 2012-02-11, Dave Hart <hart at ntp.org> wrote:
> On Sat, Feb 11, 2012 at 01:03, unruh <unruh at invalid.ca> wrote:
>> On 2012-02-09, bombjack <bombjack99 at gmail.com> wrote:
>>> What happens if I change the time on the server, lets say 5 years
>>> forward? Will the client sync to the server? and If so, how? big leap?
>>> small steps? Will the flag "-g" affect how the client reacts to this
>>> changes?
>> No. If ntp finds the time out by >128ms, it steps the clock. If it finds
>> it out by 1000(?) sec it says "Something is horribly wrong here" and
>> abandons ship. (ntpd exits).
> Don't let facts get in the way of your recollections, I suppose.
> Quoting myself from this very thread: "-g allows a single step
> exceeding the panic threshold, not necessarily at startup."  The panic
> threshold defaults to 1000 s.  But don't take my word for it -- see
> the docs.

??? a) that -g is typically used at startup and was introduced in order
to handle wildly out of sync clocks at starup. I suspect that the fact
that -g will also works if startup has been OK, but 17 days into running
it suddenly finds the clock out by 5 days is a bug in the implimentation
of -g. 
And my recollection seems to have been dead on. 
> Cheers,
> Dave Hart

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