[ntp:questions] ntpd -q and driftfile

Richard B. Gilbert rgilbert88 at comcast.net
Tue Mar 22 20:27:47 UTC 2011


On 3/22/2011 12:07 PM, bombjack 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:
>>
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>>>> 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?
>
> thanks,
> Fredrik

If you are satisfied with hours and minutes; e.g. 4:02PM you can use 
NTPDATE or NTP -g, (check this against the NPTD documentation, I'm 
running on memory and may have dropped at bit or two).  NTPDATE is
"deprecated"; it's no longer maintained or distributed.  There are, 
however, a few thousand or a few million copies either in use or just 
stored "in case we need it".

Many of the people who hang out here are trying to get a whole herd of 
computers and other devices to agree on a common time that is a 
reasonable approximation of the *correct* time.  This is necessary for 
things like analyzing log files.  Some have legal requirements for time 
stamping transactions.  Some are hobbyists who see it as a technical 
challenge.




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