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All machines are Ubuntu I need to sync clock one time for all machine in order to do a latency test.

I read this article that said -

ntpdate is a bit of a blunt instrument - it can only adjust the time once a day

and i got confused . I thought that i can run ntpdate when ever I want.

If i just want one time sync for these computers. Do you recommend me to use ntpd or ntpdate? (simplicity and accuracy) Should I setup ntp server or since they all conect at the same time to the same ntp global server than it reasonable that they will get the same offset (i dont care if they will have offset, just want that they all will have the same offset)? Which server is the simplest to configure?

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What are you actually looking to achieve? Syncing once will get the systems to the same offset at that instant, but the reason you want to keep them syncing is that they'll drift apart over time. –  Shane Madden Nov 23 '12 at 7:35
    
I need just for the latency check that these computers will have the same time. In the latency test i add timestamp on packet that move throught all these computers , so i need to sync them for the test –  Avihai Marchiano Nov 23 '12 at 14:51

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If you want the times of two or more computers to be synchronized, you should run ntpd. That will take all the guesswork away, and keep the clocks synced.

You can certainly run ntpdate periodically. Some of your machines will have clocks that are running fast, and others will be running slow. But if none of them are drifting too badly, it's fine. You run into trouble with ntpdate when a computer has a clock that's drifting badly. Some programs get confused when ntpdate whacks the clock. So, if you run ntpdate, you have to figure out how often to run it to keep the clocks in sync, depending on how quickly they're deviating from the correct time.

It's easier to simply run ntpd. Point it at pool.ntp.org and forget about it.

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Please just run ntpd. There's really no reason not to. It consumes a trivial amount of memory, and an even smaller amount of bandwidth, and prevents your clock from drifting. You're really just going to be significantly happier running ntp instead of ntpdate on a cron. –  devicenull Dec 22 '12 at 5:19

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