Re: Clock problems

[coderman <coderman@xxxxxxxxx>]

On Sun, Mar 8, 2009 at 6:16 PM, downie - <downgeoff2@xxxxxxxxxxx> wrote:
>...
> "[warn] Your system clock just jumped 160 seconds forward; assuming
> established circuits no longer work."
> There are big blocks of these errors occuring 3 minutes 40 seconds or so
> apart, for 3 hours.
> The reported clock jump is always 150-170 seconds, and always forwards.
...

this sounds like the expected behavior of ntpd issuing adjtime() calls
to slowly bring your clock skew down to current time.  this can take
hours depending on how large of an adjustment is needed.

is the computer off for a longer period of time than usual when such
behavior occurs?

from OSX adjtime man page:

DESCRIPTION
Adjtime() makes small adjustments to the system time, as returned by
gettimeofday(2), advancing or retarding it by the time specified by
the timeval delta.  If delta is negative, the clock is slowed down by
incrementing it more slowly than normal until the correction is
complete.  If delta is positive, a larger increment than normal is
used.  The skew used to perform the correction is generally a fraction
of one percent.  Thus, the time is always a monotonically increasing
function...


also, ntpd / ntpdate may also perform similar incremental adjustment themselves:

"""
[ntpd|ntpdate may] step the time using settimeofday(2) if the offset
is greater than +-128 ms.  Note that, if the offset is much greater
than +-128 ms in this case, it can take a long time (hours) to slew
the clock to the correct value.  During this time, the host should not
be used to synchronize clients.
"""

best regards,