uefi8

Overview

The UEFI Unified Extensible Firmware Interface provides boot- and run-time services to operating systems. UEFI is a replacement for the legacy BIOS on the i386 and amd64 CPU architectures, and is also used on arm, arm64 and riscv architectures.

The UEFI specification is the successor to the Extensible Firmware Interface (EFI) specification. The terms UEFI and EFI are often used interchangeably.

The UEFI boot process loads system bootstrap code located in an EFI System Partition (ESP). The ESP is a GPT or MBR partition with a specific identifier that contains an msdosfs(4) FAT file system with a specified file hierarchy.

The UEFI boot process proceeds as follows:

1. UEFI firmware runs at power up and searches for an OS loader in the EFI system partition. The path to the loader may be set by an EFI environment variable managed by efibootmgr(8). If not set, an architecture-specific default is used.

   Architecture	Default Path
   amd64	/EFI/BOOT/BOOTX64.EFI
   arm	/EFI/BOOT/BOOTARM.EFI
   arm64	/EFI/BOOT/BOOTAA64.EFI
   i386	/EFI/BOOT/BOOTIA32.EFI
   riscv	/EFI/BOOT/BOOTRISCV64.EFI

2. loader.efi reads boot configuration from /boot.config or /boot/config.

3. loader.efi loads and boots the kernel, as described in loader.efi(8).

The vt(4) system console is automatically selected when booting via UEFI.

Files

/boot/loader.efi

Final stage bootstrap

/boot/kernel/kernel

Default kernel

/boot/kernel.old/kernel

Typical non-default kernel (optional)

UEFI bootstrap