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Ali Mezgani
Asked: 2015-08-04 10:57:06 +0800 CST

Trouble with NTP Sync between ntp servers and VMs

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I have many VMs on production that run vmware, with vmtools running and the sync between ESXI and hosts is disabled. I run ntp client on all hosts, the OS of hosts is RHEL.

The problem I have is that I get many incidents about loses sync with NTP servers with important latence, please can you tell me what's wrong with my VMs ? and what I have to check to troubleshoot sync between servers ?

The ntp server is reachable and the time is maintened for a while, I get a difference of offset of 4000ms. I thought that the cause of this lose of sync is that the ESXI sychronisation was enabled and there are two sync in each vm but is it not the case.

linux

2 Answers

  1. Have you verified your NTP settings are pointing to your NTP server and communicating to the server? Or if you do not have an internal NTP server, verify that they are all pointing to the same external NTP server and that they are properly communicating to that server?

    You mention that the servers "lose sync". What does this mean exactly? Are they straying beyond an acceptable measure or are they completely unable to maintain their time (usually it will be a 5 minute difference before NTP is unable to correct the time).

    What has the offset and delay during these periods shown? (Hint: Take a look at 'ntpdc -sn' output).

    We will need a bit more information on what you have tried, the specifics of the issues/errors (need more than "it is not working") so that we can provide some suggestions on possible causes.

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  2. Depending on version of RHEL (which for whatever reason you decided not to include), you have to make sure ntpd (RHE6) or chronyd.service (RHEL7) IS running and set to start after reboot, also make sure it's configured properly.

    for more information:

    • RHEL6: ntp.conf(5), ntpq(8), ntpdc(8)
    • RHEL7: chrony(1), chronyc(1), chrony.conf(5), hwclock(8), ntpd(8)

    oh and next time, please include MORE information as that would make it easier to help YOU! also include some logging as well, your question is incomplete and that's why you're getting all those votes to close your question!

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