[ntp:questions] NTP settings for machine with irregular, short connections to the Net

Jason Rabel jason at extremeoverclocking.com
Sat Sep 8 14:07:39 UTC 2007


>> If only the human scale is required, how about ntpdate run via cron or
>> its platform-specific equivalent.  On the laptop, it would try to get
>> time from the ISP's NTP server(s).  On the other systems it would try
>> to get time from the laptop.  So, when the laptop is connected to the
>> ISP network, it gets time from there and the clients simply time-out
>> their ntpdate commands.  Then when it is on the little network, the
>> laptop's attempt at ntpdate is the one that times-out and the clients
>> get time from the laptop.

'iburst' (and possibly 'burst') will probably yield you the most benefit for
the minimal amount of time the notebook is online. You could also change the
'minpoll' & 'maxpoll' values to keep them somewhat low so ntp can build up
data faster.

>A few more points need to be made in order to make this work.
>
>The laptop needs to run ntpd while it serves time to the other LAN 
>clients. For ntpd to convince itself that it is capable of serving time 
>while not connected to the ISP, it needs permission to "synchronise to" 
>its own local clock.

Well, that's not entirely true. If he is running Windows (2K & Up) you can
use a registry hack to enable a local SNTP server. So for simplicity's sake
he doesn't actually need to install NTP (unless it is *nix).

>Given that the OP won't want to change the configuration of his laptop 
>each time he moves between the ISP and the LAN, he in fact won't be able 
>to use ntpdate to synchronise the laptop to the ISP (because ntpd will 
>be running), and instead will have to use ntpd itself for the purpose of 
>synchronising the laptop to the ISP.

I don't know how good a notebook really is for a time sync device. Mine is
horrible, I don't know if it is speed-step or what doing it, but in a single
day I could be off by quite a few seconds. I always go in & out of suspend
and hibernate so I don't run NTP on it, but I do have the Windows SNTP
client update several times a day (registry change) to keep things sane.




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