[ntp:questions] Laptop

Danny Mayer mayer at ntp.isc.org
Tue Mar 14 13:27:56 UTC 2006

Danny Mayer wrote:
> Gerriet M. Denkmann wrote:
>> On 13 Mar 2006, at 08:50, Danny Mayer wrote:
>>> Gerriet M. Denkmann wrote:
>>>> ntpd seems to require a constant internet connection (although as far
>>>> as  I can see this is never explicitly stated).
>>>> But what about a computer, which is only occasionally (on average once a
>>>> day) connected to the internet, and for a few minutes (5 minutes on
>>>> average)?
>>> ntpd was designed at a time that Internet access was unreliable and you
>>> would be dialing the NIST number in Colorado, US, to get an accurate
>>> time source. So yes, this is actually normal.
>>>> Can ntpd be used in this case?
>>> Yes.
>>>> If yes, what paramters have to be set in ntp.conf?
>>> Set up your server with iburst options and don't use any restrict lines.
>>> in the startup line add -g which will allow it to reset you clock even
>>> if the clock is way off.
>>>> If no, are there any programs available to handle this?
>>> ntpd works fine. Just restart ntpd every time you connect as the IP
>>> address of your local system will change and ntpd does not yet handle
>>> dynamic address changes on the local machine.
>> This is what I currently do.
>> But the man page says: "After one hour the frequency file is created and
>> the current frequency offset written to it." 
>> And: "It may take some hours for the frequency and offset to settle down."
>> As the laptop is almost never connected to the internet for 1 hour, the
>> drift file exists, but just contains 0.00.
>> And so every day, when the computer connects to the internet and ntpd is
>> started, the clock jumps back by 2.2 seconds.
>> I would much prefer a more continous operation.
> Someone had supplied a patch to change the default drift file write
> frequency to a configurable value. This sounds like just what you need
> for your case.
> I'll have to look to see where that stands.
It's bug #472 but it didn't make it into RC1 for some reason. Harlan?


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