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I want to prove to another team that time is in sync on around 10 Linux servers. I have checked it and it looks good (ntp is setup etc). But they need some kind of validation.

Developers are claiming some piece of their code is not working and they suspected it tied to time sync.

Any thoughts ?

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  • Ask them what they want to see?
    – Michael Hampton
    Commented Dec 13, 2018 at 16:29
  • I updated my question.
    – user1074593
    Commented Dec 13, 2018 at 16:31
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    It sounds like they need to be proving to you that time sync is the problem.
    – Michael Hampton
    Commented Dec 13, 2018 at 16:35
  • ha ha agreed. Already done that but it keeps coming back to me :(
    – user1074593
    Commented Dec 13, 2018 at 16:36
  • You need to ask them to be more specific, then.
    – Michael Hampton
    Commented Dec 13, 2018 at 16:36

2 Answers 2

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If you have at least 3 trusted time sources for your ntp client to sync to. If the output of something like ntpq -p shows them all in sync with the local host, then you're good - not a whole lot more you can do beyond that.

BTW, having 3 or more clocks to sync to is important. There is an old saying "A man with 2 watches never knows what time it is." It's true. If you have two time sources, you can never trust either of them to be true. You need at least 3 so that a consensus can be formed.

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    And better yet, use 4 time sources like the BCP documents for NTP recommend, so that if one goes down, you still have three good ones.
    – Austin Hemmelgarn
    Commented Dec 14, 2018 at 15:31
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Setup an NTP daemon on all the systems and properly configure it. Also verify that your timezones are properly configured, both in the OS, and any software you are running (eg php config, and others).

Setup a monitoring system like nagios/icinga/etc, and use the check_ntp_time plugin to check the status of time on all your systems. If you setup the right graphing plugins you can even make nice graphs showing the time offsets.

If you don't want/need a full monitoring system, you could just install the monitoring tools, and occasionally run the check_ntp_time via a script in cron or something and log/email the results or something. Maybe just put a script somewhere that these devs can directly run and see the results.

Here is an example. This checks the time of my linux desktop against the time of my router, with a warning if the offset is greater than a second, or error if greater than 5.

# check_ntp_time -H 10.1.1.1 -w 1.0 -c 5.0
NTP OK: Offset 0.004163891077 secs|offset=0.004164s;1.000000;5.000000;
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