[ntp:questions] ntpd -q and driftfile

unruh unruh at wormhole.physics.ubc.ca
Tue Mar 22 17:29:31 UTC 2011

On 2011-03-22, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> On 3/22/2011 2:56 AM, prashant sherin wrote:
>>> ntpd is intended to for continuous, not periodic running.  You are not
>>> using it correctly.
>>> Cheers,
>>> David
>> Thanks for the quick reply.
>> ntpd does allow us to run this way. From the ntpd man page:
>>   -q      Exit the ntpd just after the first time the clock is set.
>> This behavior mimics that of the ntpdate program, which is to be
>> retired. The -g and -x  options  can
>>                 be used with this option. Note: The kernel time
>> discipline is disabled with this option.
>> The idea is to use it as ntp client.
>> Thanks and Regards,
>> Prashant
> The fact that it's possible to use NTPD that way does NOT mean that it 
> is anywhere close to using NTPD as designed nor is it the best way for 
> most purposes!  You could do almost as well by setting the time from 
> from my wrist watch which uses VLF radio to receive time broadcasts.

oh, come off it. Your reaction time is nowhere near what ntp -q would
give you. Using ntp -q run once every hour, and assuming say a 20PPM
drift for the crystal, his clock would be out by less than a 100 ms due to the
drifting, and your reaction time with your watch ( and wyour watch) are
nowhere near that accurate. 

> "Normal usage" is to run NTPD 24 hours a day, 365 days a year or 366 on 
> leap years.

Agreed. That is indeed the best, but not the only way to use ntpd.
And it is not "wrong" to use it in the other way. 
It is up to him to decide what he wants running on his machine. However,
he should know what his decisions mean and right now he is confused.


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