[ntp:questions] problem with pool directive?

Rob nomail at example.com
Tue Nov 11 10:32:16 UTC 2014


Harlan Stenn <stenn at ntp.org> wrote:
> Rob writes:
>
>> There is now one remaining issue: this pool command has added 7 pool
>> servers.  That is a bit too much.
>
> ntpd doesn't think so.

I don't like to load the pool with queries from 7 servers for a setup
that only would need them to get the time when both my private servers
are down.
I could even use a "conditional" pool entry that it only starts using
when one or both of the hardwired servers fail.

>> I already have two hardwired own servers and only wanted to add maybe
>> 2 pool members to have redundancy.
>
> What about specifically using two "server" entries then?  You'll still
> need the "restrict source" directive because the IPs are unknown.

No, I tested that and the restrict source is NOT required in that case!
That is what made it so puzzling for me.

I have tried a config with two "server pool.ntp.org" lines and it just
worked.  No restrict lines other than the default required!

The reason I wanted to try the "pool" directive is that it promises to
refresh the DNS entry when the server fails.  I don't like to keep polling
the pool servers for a long time (these systems may well be up for a
year with no reboot) after they have decided to leave the pool or not
to serve time anymore.

>> I would have expected a "members" option for the pool directive, but
>> there does not appear to be one.
>
> Please describe what you think this "members" option should do.

It would determine the number of servers that "pool" attempts to add
to the running config.

> NTP is a low-load service, and accurate time can be a critical need.

In the parts of the system where we have critical time needs we have a
local GPSDO with PPS.  This is only for those systems that do not
require such accuracy, but are not on our LAN.  They are on internet
with a VPN, but I like them to acquire time even when the VPN does not
come up, and our own servers are not reachable.



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