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 user name that you use to log in to the machine from which you want to run the CLI upgrade, the path to the vCenter Server Appliance ISO file, the path to your JSON configuration file, and the string values in your JSON configuration file, including the passwords, must contain only ASCII characters. Extended ASCII and non-ASCII characters are unsupported.
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.
For topologies with external Platform Services Controller instances, you must upgrade the replicating Platform Services Controller instances in a sequence. After the successful upgrdae of all Platform Services Controller instances in the domain, you can perform concurrent upgrades of multiple vCenter Server appliances that point to a common external Platform Services Controller instance.