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Manual Pages  — UEFI

NAME

UEFI – Unified Extensible Firmware Interface bootstrapping procedures

CONTENTS

DESCRIPTION

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(5) FAT file system with a specified file hierarchy.
Partition Scheme ESP Identifier

GPT		 C12A7328-F81F-11D2-BA4B-00A0C93EC93B

MBR		 0xEF

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

    The default UEFI boot configuration for FreeBSD installs loader.efi in the default path.

  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

UEFI bootstrap
/boot/loader.efi
  Final stage bootstrap
/boot/kernel/kernel
  Default kernel
/boot/kernel.old/kernel
  Typical non-default kernel (optional)

SEE ALSO

vt(4), boot.config(5), msdosfs(5), boot(8), efibootmgr(8), efidp(8), efivar(8), gpart(8), loader.efi(8), uefisign(8)

HISTORY

EFI boot support for the ia64 architecture first appeared in FreeBSD 5.0 . UEFI boot support for amd64 first appeared in FreeBSD 10.1 ; for arm64 in FreeBSD 11.0 ; for armv6 and armv7 in FreeBSD 12.0 ; and for riscv in FreeBSD 13.0 .

BUGS

There is no support for 32-bit i386 booting via UEFI.
UEFI (8) August 31, 2023
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