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ntp config tech note

  • From: Randy Bush
  • Date: Thu May 20 15:30:28 2004

sorry to take you away from discussing spam with an actual
tech note, but twice this morning i have hit incidents where
much needed ntp clients were blown.  so, as i was gonna have
to write it up, i figured i would bore you all with it.


ntp config hint

ntpd will not work if your clock is off my a few minutes.
it just sits there forever with its finger in its ear.  so,

at boot, before you start ntpd, use ntpdate to whack your
system's time from a friendly low-numbered strat chimer.

do not background ntpdate with -b, because, if it is slow to
complete, ntpd can't get the port when you try to start it
next in the boot sequence.  

if ntpdate takes a minute and thus adds to your boot time,
then something is wrong anyway; fix it.

in case your dns resolver is slow, servers are in trouble,
etc. have an entry for your ntpdate chimer in /etc/hosts.
yes, i too hate /etc/hosts; but i have been bitten without
this hack; named is even more fragile than ntpd.

once ntpdate has run, then and only then, start your ntpd.
and read all the usual advice on configuration, selection
and solicitation of chimers with which to peer, ...

and then, if having accurate time on this host is critical,
cron a script which runs `ntpq -c peers` and pipes it to a
hack which looks to be sure that one of the chimers has a
splat in front of it.  run this script hourly, and scream
bloody hell via email if it finds problems.


now back to your regular spam discussion.  /*
   yes, spam is an important issue.  but, if your local
   organization, this mailing list, ... gets swamped with
   discussions of spam, then the spammers have won.

   you have to compartmentalize it, in your organization and
   in the general net culture.  that's why there are
   separate mailing lists for spam, ddos, and other net crap
   with which we have to deal.

   that's why we have more than one mailing list in the
   world, to compartmentalize so we can focus.