[ntp:questions] Local clock question with dialup connection

Nigel Henry cave.dnb at tiscali.fr
Sun Apr 15 18:13:34 UTC 2007


On Sunday 15 April 2007 18:58, David Woolley wrote:
> In article <200704151700.57526.cave.dnb at tiscali.fr>,
>
> cave.dnb at tiscali.fr (Nigel Henry) wrote:
> > ntpd is still running, but has timed out on trying to contact the
> > Internet timeservers.  If I stop, then restart ntpd, the timeservers are
> > contacted ok,
>
> I'm not sure what you mean by timed out.  If a server becomes unreachable,
> it will continue to be polled and will start to be used again when it
> becomes reachable again.  The two machines may drift apart in the time, but
> they will also drift from UTC, so there is a risk of a time step whatever
> you do.

I presumed that was a limit to the times that the servers would be polled, and 
if there was no response, as in the case of no Internet connection, that 
there would be be what  I would describe as a time out. What you say though 
regarding dynamic IP addresses might come into the equation. I do get a new 
dynamically assigned address each time I connect to my ISP.
>
> Adding a local clock (remembering to make the stratum as high as possible)
> to the upstream one of the pair will keep the two in step with each other,
> but may slow down the re-acquisition of the true time.  For some people,
> that is the best approach.

The local clock is set as stratum 10
>
> However, if you are on a dynamic IP address, the servers will never be
> re-acquired, and you will have to unconfigure them and reconfigure them,
> or re-start the daemon, to get their addresses resolved again, regardless
> of whether you have the local clock configued.

Based on this i'm fairly well stuffed, apart from restarting the daemon when I 
an reconnected to the Internet with a new dynamic IP address.

So what I'm looking for is a script that will run when an Internet connection 
is re-established, and will then do a /etc/init.d/ntp stop, followed by 
a /etc/init.d/ntp start. Probably too much to ask as it as has to run as 
root.

Anyway I'm happy with NTP. If I have to do a few workarounds, that's no big 
deal.

Thanks for the info.

Nigel.
>
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