Resolution
To perform an unattended installation of updates it is necessary to run the following command on a server:vzupdate.exe /unattended
It downloads and installs all available Virtuozzo Containers, Parallels Infrastructure Manager and Parallels Management Console updates.
You will be able to see progress of installation in Virtuozzo Update Wizard window.
You are strongly recommended to reboot the server as soon as the installation is finished.
Note: Some Parallels Infrastructure Manager updates can require reboot of the server before its installation.