[ntp:questions] ntpd -q and driftfile

unruh unruh at wormhole.physics.ubc.ca
Tue Mar 22 17:32:45 UTC 2011


On 2011-03-22, bombjack <bombjack99 at gmail.com> wrote:
> On Mar 22, 4:20?pm, "Richard B. Gilbert" <rgilber... 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.
>>
>> "Normal usage" is to run NTPD 24 hours a day, 365 days a year or 366 on
>> leap years.
>
> Hi,
> First: Thanks for quick response
>
> I am fully aware fo how ntpd should be used, i.e. 24/7/365, but that
> is not what I am asking for. As I stated above, I need to make sure
> the system clock is roughly (your wrist watch would do) the correct
> time ASAP during boot as other systems will use this time and can't
> easily be changed later if time deviates too much when ntpd (later)
> has initial sync. I presume you are aware of that ntpd will take some
> samples/time before syncing and that is not good enough. therefore, I
> still wonder if ntpd -q could be used in favour of rdate?

Yes. It is far better than rdate. 

IF you want rapid convergence, and you are running linux/bsd, you might
have a look at chrony which has far more rapid convergence of the time,
can be set up to initially step the clock to the right time (as can I
beleive ntp) and disciplines the clock to tighter tolerances than does
ntpd.


>
> thanks,
> Fredrik




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