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.Dd August 31, 2023 25.Dt UEFI 8 26.Os 27.Sh NAME 28.Nm UEFI 29.Nd Unified Extensible Firmware Interface bootstrapping procedures 30.Sh DESCRIPTION 31The 32.Nm 33Unified Extensible Firmware Interface provides boot- and run-time services 34to operating systems. 35.Nm 36is a replacement for the legacy BIOS on the i386 and amd64 CPU architectures, 37and is also used on arm, arm64 and riscv architectures. 38.Pp 39The UEFI specification is the successor to the Extensible Firmware Interface 40(EFI) specification. 41The terms UEFI and EFI are often used interchangeably. 42.Pp 43The 44.Nm 45boot process loads system bootstrap code located in an EFI System Partition 46(ESP). 47The ESP is a GPT or MBR partition with a specific identifier that contains an 48.Xr msdosfs 5 49FAT file system with a specified file hierarchy. 50.Bl -column -offset indent "Partition Scheme" "ESP Identifier" 51.It Sy "Partition Scheme" Ta Sy "ESP Identifier" 52.It GPT Ta C12A7328-F81F-11D2-BA4B-00A0C93EC93B 53.It MBR Ta 0xEF 54.El 55.Pp 56The 57.Nm 58boot process proceeds as follows: 59.Bl -enum -offset indent -compact 60.It 61.Nm 62firmware runs at power up and searches for an OS loader in the EFI system 63partition. 64The path to the loader may be set by an EFI environment variable managed by 65.Xr efibootmgr 8 . 66If not set, an architecture-specific default is used. 67.Bl -column -offset indent "Architecture" "Default Path" 68.It Sy Architecture Ta Sy Default Path 69.It amd64 Ta Pa /EFI/BOOT/BOOTX64.EFI 70.It arm Ta Pa /EFI/BOOT/BOOTARM.EFI 71.It arm64 Ta Pa /EFI/BOOT/BOOTAA64.EFI 72.It i386 Ta Pa /EFI/BOOT/BOOTIA32.EFI 73.It riscv Ta Pa /EFI/BOOT/BOOTRISCV64.EFI 74.El 75.Pp 76The default 77.Nm 78boot configuration for 79.Fx 80installs 81.Pa loader.efi 82in the default path. 83.It 84.Pa loader.efi 85reads boot configuration from 86.Pa /boot.config 87or 88.Pa /boot/config . 89.It 90.Pa loader.efi 91loads and boots the kernel, as described in 92.Xr loader.efi 8 . 93.El 94.Pp 95The 96.Xr vt 4 97system console is automatically selected when booting via 98.Nm . 99.Sh FILES 100.Bl -tag -width /boot/loader -compact 101.Nm 102bootstrap 103.It Pa /boot/loader.efi 104Final stage bootstrap 105.It Pa /boot/kernel/kernel 106Default kernel 107.It Pa /boot/kernel.old/kernel 108Typical non-default kernel (optional) 109.El 110.Sh SEE ALSO 111.Xr vt 4 , 112.Xr boot.config 5 , 113.Xr msdosfs 5 , 114.Xr boot 8 , 115.Xr efibootmgr 8 , 116.Xr efidp 8 , 117.Xr efivar 8 , 118.Xr gpart 8 , 119.Xr loader.efi 8 , 120.Xr uefisign 8 121.Sh HISTORY 122EFI boot support for the ia64 architecture first appeared in 123.Fx 5.0 . 124.Nm 125boot support for amd64 first appeared in 126.Fx 10.1 ; 127for arm64 in 128.Fx 11.0 ; 129for armv6 and armv7 in 130.Fx 12.0 ; 131and for riscv in 132.Fx 13.0 . 133.Sh BUGS 134There is no support for 32-bit i386 booting via UEFI. 135