1.\" Copyright (c) 2014 The FreeBSD Foundation 2.\" 3.\" Redistribution and use in source and binary forms, with or without 4.\" modification, are permitted provided that the following conditions 5.\" are met: 6.\" 1. Redistributions of source code must retain the above copyright 7.\" notice, this list of conditions and the following disclaimer. 8.\" 2. Redistributions in binary form must reproduce the above copyright 9.\" notice, this list of conditions and the following disclaimer in the 10.\" documentation and/or other materials provided with the distribution. 11.\" 12.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 13.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 14.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 15.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 16.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 17.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 18.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 19.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 20.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 21.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 22.\" SUCH DAMAGE. 23.\" 24.\" $FreeBSD$ 25.\" 26.Dd March 18, 2022 27.Dt UEFI 8 28.Os 29.Sh NAME 30.Nm UEFI 31.Nd Unified Extensible Firmware Interface bootstrapping procedures 32.Sh DESCRIPTION 33The 34.Nm 35Unified Extensible Firmware Interface provides boot- and run-time services 36to operating systems. 37.Nm 38is a replacement for the legacy BIOS on the i386 and amd64 CPU architectures, 39and is also used on arm, arm64 and riscv architectures. 40.Pp 41The UEFI specification is the successor to the Extensible Firmware Interface 42(EFI) specification. 43The terms UEFI and EFI are often used interchangeably. 44.Pp 45The 46.Nm 47boot process loads system bootstrap code located in an EFI System Partition 48(ESP). 49The ESP is a GPT or MBR partition with a specific identifier that contains an 50.Xr msdosfs 5 51FAT file system with a specified file hierarchy. 52.Bl -column -offset indent "Partition Scheme" "ESP Identifier" 53.It Sy "Partition Scheme" Ta Sy "ESP Identifier" 54.It GPT Ta C12A7328-F81F-11D2-BA4B-00A0C93EC93B 55.It MBR Ta 0xEF 56.El 57.Pp 58The 59.Nm 60boot process proceeds as follows: 61.Bl -enum -offset indent -compact 62.It 63.Nm 64firmware runs at power up and searches for an OS loader in the EFI system 65partition. 66The path to the loader may be set by an EFI environment variable managed by 67.Xr efibootmgr 8 . 68If not set, an architecture-specific default is used. 69.Bl -column -offset indent "Architecture" "Default Path" 70.It Sy Architecture Ta Sy Default Path 71.It amd64 Ta Pa /EFI/BOOT/BOOTX64.EFI 72.It arm Ta Pa /EFI/BOOT/BOOTARM.EFI 73.It arm64 Ta Pa /EFI/BOOT/BOOTAA64.EFI 74.It i386 Ta Pa /EFI/BOOT/BOOTIA32.EFI 75.It riscv Ta Pa /EFI/BOOT/BOOTRISCV64.EFI 76.El 77.Pp 78The default 79.Nm 80boot configuration for 81.Fx 82installs 83.Pa loader.efi 84in the default path. 85.It 86.Pa loader.efi 87reads boot configuration from 88.Pa /boot.config 89or 90.Pa /boot/config . 91.It 92.Pa loader.efi 93loads and boots the kernel, as described in 94.Xr loader 8 . 95.El 96.Pp 97The 98.Xr vt 4 99system console is automatically selected when booting via 100.Nm . 101.Sh FILES 102.Bl -tag -width /boot/loader -compact 103.Nm 104bootstrap 105.It Pa /boot/loader.efi 106Final stage bootstrap 107.It Pa /boot/kernel/kernel 108Default kernel 109.It Pa /boot/kernel.old/kernel 110Typical non-default kernel (optional) 111.El 112.Sh SEE ALSO 113.Xr vt 4 , 114.Xr boot.config 5 , 115.Xr msdosfs 5 , 116.Xr boot 8 , 117.Xr efibootmgr 8 , 118.Xr efidp 8 , 119.Xr efivar 8 , 120.Xr gpart 8 , 121.Xr uefisign 8 122.Sh HISTORY 123EFI boot support for the ia64 architecture first appeared in 124.Fx 5.0 . 125.Nm 126boot support for amd64 first appeared in 127.Fx 10.1 ; 128for arm64 in 129.Fx 11.0 ; 130for armv6 and armv7 in 131.Fx 12.0 ; 132and for riscv in 133.Fx 13.0 . 134.Sh BUGS 135There is no support for 32-bit i386 booting via UEFI. 136