[ntp:questions] Re: ntpd, boot time, and hot plugging

Brad Knowles brad at stop.mail-abuse.org
Thu Feb 3 23:55:01 UTC 2005


At 9:03 PM -0200 2005-02-03, Alain wrote:

>  So, if I manage to set the initial time within a good aproximation od
>  "real" time using ntpdate using 5 servers as explained earlyer, would
>  you recomend to delete the drift file and let it start all over again?

	If the drift file states +/- 500ms, then I would be inclined to 
remove it on startup no matter what.  Of course, I would also be 
inclined to use "ntpd -g" instead of ntpdate, for the reasons I've 
previously given you, not to mention the issues that you have 
mentioned here regarding the use of ntpdate against servers that are 
not up.

>  Does this afect the time for the server to start serving?

	If the drift file is whacked out, it's better to remove it and 
let the server re-calculate, than to try to compensate for a whacked 
out drift file.  You'll start serving time faster if you let the 
system try to calculate the real situation once the clock has been 
set to a reasonable value on startup.

	Keep in mind that the server will have to take extra time to get 
to a state where it can start serving time to clients, if it has had 
to calculate a new drift file or try to deal with a whacked out drift 
file.  If you're sensitive to seven seconds of additional startup 
time, then you really, really want to make sure that you always keep 
a reasonable drift file.


	Given the kinds of time periods we're talking about, I still have 
yet to see a good reason for using "ntpdate; ntpd" instead of "ntpd 
-g".

-- 
Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.



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