OT NTP [Re: how can I not have to spend 40 minutes _waiting_ in the morning for each of 40 updates?]

[Todd Denniston]

chaitu wrote, On 10/09/2008 04:17 PM:
> Hi Todd/Arthur,
>
> Thanks for the insights. Unfortunately for me, I am that typical
> "young configuration manager" that software companies can afford
> easily when they dont have the patience or money to look for an
> expert. But with sound advice I intend to learn quickly and do my job
> well. Thanks a lot for your help especially!!
Glad to be of help.

> The exact background of the problem is here (I hope this answers your
> questions):
>
> 1. All 40 are different operating systems....well technically they are
> mostly Linux
<SNIP>
> 3. The cvs update command is not part of the build process, so the
<SNIP>
> I do
> observe the problem of the client boxes losing time daily........these
> linux boxes are connected to a Windows NT domain and for keeping
> correct time I have configured the NTPD on them by pointing to some
> servers in nasa.gov. But in spite of that the boxes lose time
> regularly....it's a nuisance I could not fix in the last 2 yrs (but
> that's for another thread in another forum, I guess). Does it sound
> ominous to you?
<SNIP>


A reasonably correct ntpd setup would be to have 2 or 3 of your machines 
peering together to follow reasonable sources such as nasa.gov, 
0.pool.ntp.org, 1.asia.pool.ntp.org, or in.pool.ntp.org [1].
and then all of your other machines should be following the 2 or 3 machines 
that are following the outside world.
Also to _one_ of the in.pool.ntp.org server lines on _one_ of the outside 
following machines I would add
maxpoll 12 burst
to the end of the server line, which lets it not hit the sever as often (only 
once every 4096 seconds), but when it does it hits it 8 (times in a minute) to 
get a really good reading. This probably still violates the 'Rules of 
Engagement'[2] but if you can't get a stable clock otherwise, something has to 
be done.
Of course if you had a bit of money to spend and some time to set it up, you 
could have your own reference clock[3] to go along with what you get from the 
world[1].



BTW I have been assuming you are running all your boxes on real hardware, 
because it is a known problem with vmware (other VMs may be affected, but I 
have had experience with vmware) that the hosted platform will not be able to 
keep good time.  If you are on vmware, periodic(cron) use of `hwclock hctosys` 
in the VM hosted OS, with the bare metal OS using NTP is the better option.


[1] a group of folks have banded together to help try to have a good time 
around the world :)
see http://www.pool.ntp.org/
in.pool.ntp.org is an pool for India, if I understand 
http://www.pool.ntp.org/zone/asia
also see: http://www.pool.ntp.org/use.html

[2] http://support.ntp.org/bin/view/Servers/RulesOfEngagement

[3] http://support.ntp.org/bin/view/Support/InexpensiveOemGps
http://support.ntp.org/bin/view/Support/DesigningYourNTPNetwork
http://support.ntp.org/bin/view/Support/ConfiguringNTP

--
Todd Denniston
Crane Division, Naval Surface Warfare Center (NSWC Crane)
Harnessing the Power of Technology for the Warfighter