UEFI(8)

NAME
UEFI - Unified Extensible Firmware Interface bootstrapping procedures

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 arm64 and ia64.

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 msdos(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. If not set, the default is /EFI/BOOT/BOOTX64.EFI. The default UEFI boot configuration for DragonFly installs boot1.efi as /EFI/BOOT/BOOTX64.EFI.
2.  boot1.efi reads boot configuration from /boot.config or /boot/config. Unlike other first-stage boot loaders, boot1.efi passes the configuration to the next stage boot loader and does not itself act on the contents of the file.
3.  boot1.efi searches partitions of type ‘DragonFly UFS1’ and the first disklabel64(5) partition in GPT partitions of type ‘DragonFly Label64’ for loader.efi. The search begins with partitions on the device from which boot1.efi was loaded, and continues with other available partitions. boot1.efi then loads and executes loader.efi.
4.  loader.efi loads and boots the kernel, as described in loader(8).

FILES
/boot/boot1.efi
    First stage UEFI bootstrap
/boot/loader.efi
    Final stage bootstrap
/boot/kernel/kernel
    default kernel
/boot/kernel.old/kernel
    typical non-default kernel (optional)

SEE ALSO
efivar(3), disklabel64(5), msdos(5), boot(8), efibootmgr(8), efidp(8), efisetup(8), efivar(8), uefisign(8)

HISTORY
UEFI boot support first appeared in FreeBSD 10.1 and was brought into DragonFly 4.5.

AUTHORS
-nosplit UEFI boot support was developed by Benno Rice <benno@FreeBSD.org>, Ed Maste <emaste@FreeBSD.org>, and Nathan Whitehorn <nwhitehorn@FreeBSD.org>. The FreeBSD Foundation sponsored portions of the work.

CAVEATS
EFI environment variables are not supported by loader(8) or the kernel.