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Q. How should I manage time synchronization in VMware virtual machines (VMs)?

A. You should already know that time in VMs gets skewed because of virtualization effects. VMs that don't receive attention from their hypervisor will eventually have their time skewed unless there's a mechanism in place to fix it. Typically, you can synchronize time between VMware VMs and the real world either using the VMware Tools built-in synchronization service or through some kind of NTP client.

You must have the VMware Tools installed into a guest OS to use its time synchronization service. You can turn on periodic synchronization from within the VMware Tools control panel inside the guest OS. Alternatively, you can set the tools.syncTime=true configuration file option in the VM's .VMX file to turn on this periodic tune up.

The VMware Tools' time resolution is fairly coarse. It only verifies its time against the local OS, and only once per minute by default. That interval can be modified by adjusting the tools.syncTime.period value in the VM's .VMX file to a desired number of seconds.

That resolution might not be enough for some computing requirements. If your time resolution requirements are greater than what the VMware Tools can provide, consider installing an NTP client into each VM. If you use an NTP client in the VM, VMware recommends disabling periodic clock synchronization, but not disabling VMware Tools altogether. In addition to its periodic clock synchronization, VMware Tools also perform additional time synchronization at startup, as well as after being resumed from suspend or restored from a snapshot.

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