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When you install VMware Tools into a guest from the ISO images that came with ESXi, you'll get a status of OK, not running, or out of date. The out of date status indicates that the host has a newer version available than the guest is running. So if you've updated from ESXi 3.5 to ESXi 4.1, you'll see that status.
Unmanaged is a status shown when you install Operating System Specific Packages for VMware Tools (OSPs). These are available for a number of flavors of Linux. You can read about those options at the below links. If you have guests that show a status of unmanaged then you should not use the ISO vmware tools image that comes with ESXi to update that guest.
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