Milter-greylist

nlin wrote:
 > Emmanuel Dreyfus wrote:
 > > nlin wrote:
 > > > Does anyone know why it's doing that? I'm planning to upgrade
 > > > the other server today. But just trying to figure out why the
 > > > autowhitelist would be a negative number to begin with.
 > > 
 > > System clock skew?
 > 
 > Strange.  The two servers are synced up to ntpd server via a cron job every 
 > 30 minutes though.

Which is a perfect way to introduce system clock skew.  :-)

If you run ntpdate (or similar) at regular intervals, the
clock might be forced to make jumps, forward or backwards.
Normally, applications are not prepared to handle that
and might cause all kinds of subtle malfunctions.  I even
had cases where apps hung because they saw the same time
stamp twice during a time-out calculation.  Another typical
symptom is Makefiles sometimes failing randomly without
apparent reason.

It is much better to not run any time adjustments via cron,
but instead run ntpd as a daemon.  It will correct the
system clock continuously without jumps (except for an
initial jump at boot time if necessary, which shouldn't be
harmful).  Another advantage is that ntpd records the
drift of the local hardware clock, so it can correct it
even if you lose connection to your upstream NTP servers.

ntpdate is bad and should never be used.  I think it has
even been officially deprecated and will be removed in the
future (at least the manpage says so).

Best regards
   Oliver

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