[ntp:questions] iburst

George N. White III aa056 at chebucto.ns.ca
Fri Dec 1 00:17:42 UTC 2006


On Tue, 28 Nov 2006, Uwe Klein wrote:

> You are here:
>        echo -n $"$prog: Synchronizing with time server: "
>        /usr/sbin/ntpdate $dropstr -s -b $tickers 2>/dev/null >/dev/null
>
> i.e. the clock is hard set on start up.
>
> echo the ntpdate line to stderr to see what args are used.
> 	echo "/usr/sbin/ntpdate $dropstr -s -b $tickers " >&2
>
> If the server connections run into silent dropping of packets this
> takes for ages to time out.
>
> Incidentally i have a similar problem with invoking "ntpq -c peers"
> on a host that has a funky DNS. takes for ages.

There are even more extreme cases (e.g., ppp via modem) where typical 
startup scripts try to start the ntp service before the network is up.

There are other ntp clients that are better suited to sites with 
intermittent operation or network access, but they will still suffer from 
the problems of temperature changes in systems that run intermittently.

You can construct a list of server IP numbers using the pool URL's to get 
avoid delays due to DNS issues.  This should be legit, since a normal 24/7 
ntp client will establish a list of servers at startup and continue 
to use the same servers for as long as they are running.

For systems that run continuously but don't have reliable network access 
I've had good results using chrony <http://chrony.sunsite.dk/>:

   "It  is designed so that it can work on computers which only have inter-
   mittent access to reference sources, for example computers which use  a
   dial-up  account  to  access  the Internet. "

I'd try letting chronyd run continuously overnight to get a good 
drift value, then switch to the power conserving regime and see what 
happens.

Many systems can measure temperature at various places on the system 
board.  Maybe this could be used to develop a relationship between drift 
and startup so the drift value could be fudged on cold starts.

-- 
George N. White III  <aa056 at chebucto.ns.ca>




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