If a host was deployed using vSphere Auto Deploy, you can use Auto Deploy to reprovision the host with a new image profile that contains a different version of ESXi. You can use the ESXi Image Builder PowerCLI to create and manage image profiles.
If you upgrade the host to use an ESXi 6.0 or later image, the Auto Deploy server provisions the ESXi host with certificates that are signed by VMCA. If you are currently using custom certificates, you can set up the host to use the custom certificates after the upgrade.
The Auto Deploy server is automatically upgraded if you upgrade the corresponding vCenter Server system to version 6. Starting with version 6, the Auto Deploy server is always on the same management node as the vCenter Server system.