When you install VMware Tools into a guest VM there is an option we are all familiar with, “Time synchronization between the virtual machine and the ESX Server”. Even with this setting unchecked what you probably don’t realise is that there are “special ” events that will still initiate a. If you turn on this advanced setting for time synchronization, the VMware Tools service, which runs inside the guest operating system, checks once every minute to determine whether the clocks on the guest and host operating systems still match. If not, the clock on the guest operating system is synchronized to match the clock on the host. Using the System Console to Configure VMware Tools in a NetWare Guest Operating System You can configure certain virtual machine options such as time synchronization, CPU idling and device configuration with VMware Tools in a NetWare virtual machine using the system console.
Using vmware vsphere server 6.0.0 with a VM running Windows 2016. I have Windows set up to sync time with time.nist.gov. The machine is using UTC time zone. After restoring to a snapshot the time does not update for a while (if ever?). I've tried various w32tm.exe commands to try to force resync but it says that the time difference is too large (it's usually off by days or weeks).
The only way I've been able to get it to update immediately is to go into this dialog and change the time server then click update now. Then change it back:
Vmware Tools Time Sync Registry Windows 10
This didn't happen with Windows 2012 in the same setup. I expect that after restoring a snapshot the time will sync immediately. Perhaps something changed in Windows 2016 and I need to do something differently before taking the snapshot or after restoring it? Or maybe something needs to be configured differently in vsphere?
1 Answer
As per VMware KB 1189, Vmware tools will usually sync time from the host when you take or restore a snapshot. So if you ensure that your host's time is reasonable then you shouldn't encounter excessive time difference and can use w32tm /resync to resync NTP. I would configure NTP on the hosts in Host > Configuration > Time Configuration > Properties and see if this helps.
EDIT: Also, according to MS KB 884776 you can configure registry entries that will allow the W32Time service to sync regardless of the size of the time difference. Set HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesW32TimeConfigMaxPosPhaseCorrection and MaxNegPhaseCorrection to 0xFFFFFFF
This value enables the computer to receive the time that is contained in any time sample, regardless of inaccuracy.
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