[ntp:questions] ntpd on dial up machine: no DNS resolving => giving up on all servers

Danny Mayer mayer at ntp.org
Sun Jun 7 16:35:58 UTC 2009

Arno Wald wrote:
> Harlan Stenn wrote:
>> There is an option to have ntpd retry failed DNS lookups for "longer". 
>> This is in ntp-dev however (which is about to become ntp-4.2.6).
> It would be good if a retry for a lookup would be started in case of a new 
> network interface is showing up, too.

There is no need to do that it just if the interface changed unless you
have radically changed locations. When I complete the work for new
lookups I will try and make that a configuration option but it's usually
not necessary by default.

> Also if a ntp-server is no longer reachable it would be good to recheck the 
> IP address. E.g. if you are using a ntp-server-pool name and retrieve a 
> "random" IP address from this pool and the server is going offline after 
> some days, it would be a good idea to retrieve a new IP address.

Yes, that's in the work I'm doing.

>> Use IP numbers instead of names.
> I do not like to hard wire IP addresses in configs. It is less robust IMHO. 
> Also you drop the functionality of using server-pools.


>> Get a reasonably inexpensive GPS device and use that for time (or if
>> geographically convenient, one of the radio refclocks).
> This is a nice idea. But maybe it is a little bit oversized for just a 
> simple working PC? But I keept it in mind.
>> You really only want to prevent ntpd from stepping the time backwards.
> Yes, right.

That really depends on the circumstances. You should not care if you
have just rebooted your system, but you will care if you have a database
which timestamps records as they are entered or updated.


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