Manual Pages  — UEFI

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. If not set, an architecture-specific default is used.

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

   The default UEFI boot configuration for FreeBSD installs boot1.efi in the default path.

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 freebsd-ufs and freebsd-zfs for loader.efi. The search begins with partitions on the device from which boot1.efi was loaded, and continues with other available partitions. If both freebsd-ufs and freebsd-zfs partitions exist on the same device the freebsd-zfs partition is preferred. boot1.efi then loads and executes loader.efi.
4. loader.efi loads and boots the kernel, as described in loader(8).

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