Virtuozzo is a container-based virtualization solution employed by a large number of service providers. Each Virtuozzo container is a separate virtual server that acts exactly like a stand-alone one.
The main way of installing an app to Virtuozzo Containers is to use a Virtuozzo template. A Virtuozzo app template is a package containing everything an app needs to be installed to a server. You install an app template to your server just once and then install the app from the template to a number of containers simultaneously. The main benefit of using Virtuozzo templates is that the software installed in containers is unified - you have one Virtuozzo template that is applied to all containers on your hardware node. If Plesk was installed to a container via a Virtuozzo template, we strongly recommend that you perform all further Plesk upgrades via templates. If you have a number of Plesk containers, this will allow you to keep all Plesk installations consistent within your hardware node.
Upgrade via Virtuozzo templates is performed in two steps: you install the latest available Plesk template to your hardware node and then start an upgrade on each container with the help of Virtuozzo commands.
As well as in the other upgrade scenarios, after the upgrade in Virtuozzo, Plesk may require the installation of a new license key. You can do this either manually or automatically. For more information about installing a license key after upgrade, refer to the section Installing a License Key.
In this section, we will describe how to perform an upgrade of Plesk installed to a Virtuozzo container via a Virtuozzo template on both Linux and Windows platforms.