During operating system installations in Unified Extensible Firmware Interface (UEFI) mode, operating system installers will create UEFI Boot variables to be used in BIOS menus to select the operating system to boot. To avoid potential loss of a boot variable created by the operating system installer, you should not use any operating system tools or utilities to manage (create, modify, or delete) these boot variables. Loss of a boot variable will preclude users from being able to boot the operating system.
All supported UEFI-capable operating systems
Releases 1.0, 1.1, 1.2, 1.3, 1.4.4, 1.5, 1.6, and 1.8
If a UEFI Boot variable is lost, reinstall the operating system so as to create a new UEFI Boot variable.