[ntp:questions] simple nt.conf cases for ntp-client

ardi peter.knezel at gmail.com
Thu Jan 23 09:18:44 UTC 2014


On Thursday, January 23, 2014 9:25:16 AM UTC+1, David Woolley wrote:
> On 23/01/14 07:29, ardi wrote:
> 
> 
> 
> >
> 
> > Why should i need the restrict line xx.xx.xx.xx?
> 
> > What does the first restrict line means?
> 
> 
> 
> You don't.
> 
> See the documentation.  Sets a fairly safe environment in which you can 
> 
> be used as a server, but not much else, by the general public.
> 
> 

Then I am still lost to understand using the restrict ...:-(
Will the following lines on client's ntp.conf be enough?:

restrict default noquery nomodify notrap
restrict 127.0.0.1
driftfile /var/lib/ntp/ntp.drift
server xx.xx.xx.xx  


> 
> >
> 
> > b1)In case using 2 ntp-servers from which my ntp-client can get time,
> 
> > is my ntp-client taking time from xx.xx.xx.xx
> 
> > and if this server is not reachable then from xx.xx.xx.yy?
> 
> 
> 
> No.  It is using a weighted average of both.
> 
> 
> 
> >
> 
> > What happens if xx.xx.xx.xx comes up again?
> 
> > Does client take time again from the xx.xx.xx.xx?
> 
> 
> 
> It starts using both again.
> 
> >
> 
> > b2)
> 
> > What does prefer do in this case b2)?
> 
> > Is there any difference between b1) and b2) case?
> 
> >
> 
> 
> 
> Never investigated prefer in detail.
> 
> >
> 
> > b3)
> 
> > what about this case b3) below?
> 
> > Is time taken for the ntp-client according to order of lines - i mean the xx.xx.xx.xx is taken as time source?
> 
> > or the 2nd server xx.xx.xx.yy is preferred?
> 
> 
> 
> See b1.  The only time the order of servers may have an effect is if you 
> 
> exceed the maximum number, and I'm not sure of that case.  Otherwise 
> 
> time quality metrics determine the weighting of the contribution of each 
> 
> server and which one is the figurehead system peer (there is also some 
> 
> hysteresis to avoid system peers changing too often).  I am pretty sure 
> 
> that the effect of the order is not specified.



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