[ntp:questions] Re: simple time server

Richard B. Gilbert rgilbert88 at comcast.net
Thu Aug 3 03:57:47 UTC 2006


Bryan Henderson wrote:

>>It takes a couple of hours for the program to figure out "what the time 
>>is precisely".
> 
> 
> Remember that in this thread, I'm talking about a situation where the
> local clock of one computer is the time standard.  If the time server
> is running on that computer, it knows by definition at all times
> precisely what time it is.
> 
> There is a whole class of applications of network time service where
> it's important that a bunch of computers adhere to a time standard,
> but that standard doesn't have to be UTC.  There's also a whole class
> of applications where wristwatch level precision is adequate.  In my
> case, I can't imagine making use of more than about 100 ms precision.
> 
> I think I've discovered in my brief investigation of the Ntpd
> reference implementation that it is not appropriate for those
> applications.  I'm still trying to figure out whether NTP itself is.
> 

If you are willing to settle for time to the nearest second you can use 
rdate.  If you need better; e.g. time to the nearest 100 milliseconds or 
better, SNTP *might* do it for you but I wouldn't want to rely on it myself.

You can, if you wish, use ntpdate to set your clocks from some NTP 
server.  You could run it in a cron job once an hour or something like 
that and it should keep your clock within a hundred milliseconds of the 
server unless you have a machine with a really bad local clock.  Ntpdate 
does not provide the full functionality of ntpd and it is "deprecated" 
and sooner or later will be dropped from the distribution.




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