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F.2.2. UEFI-based x86 systems

The Unified Extensible Firmware Interface (UEFI) is designed, like BIOS, to control the boot process (through boot services) and to provide an interface between system firmware and an operating system (through runtime services). Unlike BIOS, it features its own architecture, independent of the CPU, and its own device drivers. UEFI can mount partitions and read certain file systems.
When an x86 computer equipped with UEFI boots, the interface searches the system storage for a partition labeled with a specific globally unique identifier (GUID) that marks it as the EFI System Partition (ESP). This partition contains applications compiled for the EFI architecture, which might include bootloaders for operating systems and utility software. UEFI systems include an EFI boot manager that can boot the system from a default configuration, or prompt a user to choose an operating system to boot. When a bootloader is selected, manually or automatically, UEFI reads it into memory and yields control of the boot process to it.