Auto Deploy is a new feature in vSphere 5.0. Working with hosts managed by vCenter Server, Auto Deploy loads the ESXi image directly into the host memory, rather than installing it on the host hard disk. Therefore Auto Deploy cannot be used to upgrade or migrate version 4.x ESX and ESXi hosts to ESXi 5.0, as version 4.x ESX and ESXi hosts are deployed by the traditional method of installing the software on the host hard disk. But once a host is deployed with Auto Deploy, you can use Auto Deploy to upgrade or apply patches to the host, clearly replacing VUM.To do this, you reprovision the host by rebooting it with a new image profile that contains the ESXi upgrade or patch, a host configuration profile, and,optionally, third-party drivers or management agents provided by VMware partners. You can build custom images by using ESXi Image Builder CLI.