You can use the CLI installer to perform an unattended upgrade of a vCenter Server Appliance or Platform Services Controller appliance on an ESXi host or vCenter Server instance.
The CLI upgrade process includes downloading the vCenter Server Appliance installer on a network virtual machine or physical server from which you want to perform the upgrade, preparing a JSON configuration file with the upgrade information, and running the upgrade command.
The vCenter Server Appliance ISO file contains templates of JSON files that contain the minimum configuration parameters that are required for upgrading a vCenter Server Appliance or Platform Services Controller appliance. For information about preparing JSON templates for CLI upgrade of the vCenter Server Appliance and Platform Services Controller appliance, see Prepare Your JSON Configuration File for CLI Upgrade.