NAME
UEFI —
Unified Extensible Firmware Interface
bootstrapping procedures
DESCRIPTION
TheUEFI 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:
UEFIfirmware 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 defaultUEFIboot configuration for DragonFly installs boot1.efi as /EFI/BOOT/BOOTX64.EFI.- 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.
- 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.
- loader.efi loads and boots the kernel, as described in loader(8).
FILES
- /boot/boot1.efi
- First stage
UEFIbootstrap - /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), efisetup(8), efivar(8), uefisign(8)
HISTORY
UEFI boot support first appeared in
FreeBSD 10.1 and was brought into
DragonFly 4.5.
AUTHORS
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.