[ntp:questions] Will ntpd tell me if it encounters problems?

David Woolley david at djwhome.demon.co.uk
Thu Apr 12 06:25:27 UTC 2007


In article <1176350563.617445.166520 at l77g2000hsb.googlegroups.com>,
gluino at gmail.com wrote:

> Anyway, I'm happy with keeping my machines within say 1/4 seconds of
> UTC, considering that for many years the the company network

You need to do better than that if you want to avoid time steps, as ntpd
will step if the local clock apears to differ from the estimated time
from the servers by more than one eighth of a second, for a significant
amouunt of time (about 15 minutes).  A quarter second delay only results
in a worst case eighth second error, and then only if it is possible
for transmission in one direction to have no effective delay.

> not sure what to check for, will the asterisk always disappear after a
> problem?

It should never disappear (except during a time step), as your local clock
will never fail, which is one of the reasons why you should think whether
you really need the local clock driver; the local clock driver prevents
the time being marked invalid when you lose real servers.  It will move,
so you could check for no asterisk or asterisk on the local clock line.

I think a more reliable test would be to monitor the stratum.

ntpd also has a trap reporting mechanism, but I don't know of any
standard trap receiver for ntpd and you will still have the problem
of inferring the failure as the local clock will prevent ntpd detecting
it as a failure.

> If so, I would just check for presence of the string:
> "*203.117.180.36" (it's my government's public time server)

But you lose a lot of the benefit of your fallback servers.




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