The following are required for automatic upgrades:
Virtual machines must have a version of VMware Tools shipped with ESX Server 3.0.1 or greater installed.
Virtual machines must be hosted on an ESX Server 3.0.1 or greater, and the vCenter Server must be version 2.0.1 or greater.
Virtual machines must be running a Linux or Windows guest operating system that is supported by ESX Server 3.0.1 or greater and vCenter 2.0.1 or greater.
Virtual machines must be powered on.
To configure virtual machines to automatically upgrade VMware Tools:
Power off the virtual machine.
Right-click the virtual machine and click Edit Settings.
On the Options tab, click VMware Tools.
In the Advanced pane, select Check and upgrade Tools before each power-on and click OK.
Note: The next time the virtual machine is powered on, it checks the ESX/ESXi host for a newer version of VMware Tools. If one is available, it is installed and the guest operating system is restarted (if required).
The VMware Tools version in this scenario is checked only at virtual machine boot time. If you cannot reboot a virtual machine, upgrade the VMware Tools manually or schedule Update Manager to do so.
You may need to reboot the virtual machine after upgrading.
Based on VMware KB 1010796