VMware

VMWare & Time Synchronization: Disabling using vmtoolsd.exe timesync

Hey all,

We’ve been having some timing issues in our environment on and off. It seems that some machines are losing their time configuration and are attempting to get their time set from the local CMOS battery, which is the host that the VM resides. I thought I had read somewhere that we should run C:\Program Files\VMware\VMware Tools\vmtoolsd.exe timesync disable.

My question is: Does this only need to be done on the remote site domain controllers, or does it have to be done on every single domain joined virtual machine?

Is it going to completely stop the machine from trying to check time using local CMOS, or do I have to go through every single VM, edit the VMX, and set the options so that time synchronization is false?

Thanks!


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5 Comments

  1. It will still sync the time on vMotions and a few other activities like power on. Make sure your hosts have the correct time (via NTP) and don’t worry about it. Windows machines should have the sync from tools off and get their time from the domain.

  2. On the Windows side, do you have a policy to set a time server like Microsoft or a local NTP like your DC? You don’t want CMOS time sync as a VM speeds up and slows down so the time would go out of sync. It’s emulated hardware so it just doesn’t work the same as a bare metal server. The command you are using is the correct one for the VMware side.

  3. VMware recommends NOT using the timesync feature of VMware Tools (or open-vm-tools). Timesync is disabled by default. If you have enabled it manually, you have to disable it again on every VM. There are PowerCLI scripts that set options under ‘advanced settings’ which prevent time sync too – but then you need to reboot your VM

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