[Novalug] linux fundamentals: ntpd

Derek LaHousse dlahouss@mtu.edu
Mon Mar 2 16:38:13 EST 2015


I think Debian calls it ntpd and rpm calls it ntp.  Sorry.

On Mon, Mar 2, 2015 at 3:58 PM, pereira via Novalug
<novalug@firemountain.net> wrote:
> Hi,
>
> I checked (I think) and 'locate' can't find ntpd; 'man ntpd' doesn't exist
> either.
>
> Do I need it? Which package is it in?
>
> Nino
>
>
> On 03/02/2015 01:46 PM, Jon LaBadie via Novalug wrote:
>>
>> On Mon, Mar 02, 2015 at 09:32:24AM -0800, Walt Smith via Novalug wrote:
>>>
>>> HI,
>>>
>>> I've had years of linux boxes that don't seem
>>> preconfigured to sync nptd.  I'm not sur ewhy that
>>> is.  OR I missed something, which is why I'm here.
>>>
>>>
>>> I do:
>>> service ntpd restart
>>> # wait a few minutes
>>> service ntpd stop
>>>
>>> Then wait for the gnome desktop in CentoOS 6.x
>>> to sync up.  Thats fine.  Based on prior reading, I would
>>> expect a magic number ( for drift ) to be placed somewhere.
>>>
>>>
>>> However, nptd doesn't seem to retain the data that helps
>>> keep the system clock in sync:   ( here's where I might
>>> distinguish system ( software ) clock from the hardware clock ).
>>
>> Perhaps your "few minutes" were too short.  Check this from
>> the man page, particularly the 2nd and 3rd sentences.
>>
>>    "The frequency file, usually called ntp.drift, contains the
>>     latest estimate of clock frequency. If this file does not
>>     exist when ntpd is started, it enters a special mode
>>     designed to measure the particular frequency directly.
>>     The measurement takes 15 minutes, after which the frequency
>>     is set and ntpd resumes normal mode where the time and
>>     frequency are continuously adjusted.  The frequency file is
>>     updated at intervals of an hour or more depending on the
>>     measured clock stability."
>>
>>> I simply don't want to run nptd all the time, and believe
>>> over several months the magic number which should have
>>> been  saved should  keep the clock pretty accurate.
>>
>> As an alternative to ntpd, consider running ntpdate
>> periodically from cron.
>>
>>> So, I guess it's a 2 part q:
>>> 1. Why do the distros not set this up.
>>> 2.  What is needed to make this happen ?
>>>
>>> A quick read of the man page seems to indicate the user needs to start
>>> ntpd with a "drift" filename option.  But, also,  how does the system
>>> clock
>>> stay in sync if I don't run nptd all the time.... ( maybe I should )?
>>> I would think aquiring the accurate time over some network,
>>> and performing a box clock sync ( system or hardware) would be 2
>>> different
>>> functions...
>>>
>>> In retrospect, I guess I'd like to aquire drift every 6 months, and sync
>>> once a day or week??  (I don't need extreme accuracy).
>>>
>> For a long time I ran ntpdate a couple of times a day.
>> Given multiple time servers it improves its accuracy by
>> adjusting for network transit times.  I collected a bunch
>> of time server addresses and randomly picked 4 each cron run.
>>
>> jl
>
>
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