1.\" Copyright (c) 2014 The FreeBSD Foundation 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd January 25, 2018 28.Dt UEFI 8 29.Os 30.Sh NAME 31.Nm UEFI 32.Nd Unified Extensible Firmware Interface bootstrapping procedures 33.Sh DESCRIPTION 34The 35.Nm 36Unified Extensible Firmware Interface provides boot- and run-time services 37to operating systems. 38.Nm 39is a replacement for the legacy BIOS on the i386 and amd64 CPU architectures, 40and is also used on arm, arm64 and ia64. 41.Pp 42The UEFI specification is the successor to the Extensible Firmware Interface 43(EFI) specification. 44The terms are often used interchangeably. 45.Pp 46The 47.Nm 48boot process loads system bootstrap code located in an EFI System Partition 49(ESP). 50The ESP is a GPT or MBR partition with a specific identifier that contains an 51.Xr msdosfs 5 52FAT file system with a specified file hierarchy. 53.Bl -column -offset indent ".Sy Partition Scheme" ".Sy ESP Identifier" 54.It Sy "Partition Scheme" Ta Sy "ESP Identifier" 55.It GPT Ta C12A7328-F81F-11D2-BA4B-00A0C93EC93B 56.It MBR Ta 0xEF 57.El 58.Pp 59The 60.Nm 61boot process proceeds as follows: 62.Bl -enum -offset indent -compact 63.It 64.Nm 65firmware runs at power up and searches for an OS loader in the EFI system 66partition. 67The path to the loader may be set by an EFI environment variable. 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 arm64 Ta Pa /EFI/BOOT/BOOTAA64.EFI 73.El 74.Pp 75The default 76.Nm 77boot configuration for 78.Fx 79installs 80.Pa boot1.efi 81in the default path. 82.It 83.Pa boot1.efi 84reads boot configuration from 85.Pa /boot.config 86or 87.Pa /boot/config . 88Unlike other first-stage boot loaders, 89.Pa boot1.efi 90passes the configuration to the next stage boot loader and does not 91itself act on the contents of the file. 92.It 93.Pa boot1.efi 94searches partitions of type 95.Li freebsd-ufs 96and 97.Li freebsd-zfs 98for 99.Pa loader.efi . 100The search begins with partitions on the device from which 101.Pa boot1.efi 102was loaded, and continues with other available partitions. 103If both 104.Li freebsd-ufs 105and 106.Li freebsd-zfs 107partitions exist on the same device the 108.Li freebsd-zfs 109partition is preferred. 110.Pa boot1.efi 111then loads and executes 112.Pa loader.efi . 113.It 114.Pa loader.efi 115loads and boots the kernel, as described in 116.Xr loader 8 . 117.El 118.Pp 119The 120.Xr vt 4 121system console is automatically selected when booting via 122.Nm . 123.Sh FILES 124.Bl -tag -width /boot/loader -compact 125.It Pa /boot/boot1.efi 126First stage 127.Nm 128bootstrap 129.It Pa /boot/boot1.efifat 130.Xr msdosfs 5 131FAT file system image containing 132.Pa boot1.efi 133for use by 134.Xr bsdinstall 8 135and the 136.Ar bootcode 137argument to 138.Xr gpart 8 . 139.It Pa /boot/loader.efi 140Final stage bootstrap 141.It Pa /boot/kernel/kernel 142default kernel 143.It Pa /boot/kernel.old/kernel 144typical non-default kernel (optional) 145.El 146.Sh SEE ALSO 147.Xr vt 4 , 148.Xr boot.config 5 , 149.Xr msdosfs 5 , 150.Xr boot 8 , 151.Xr efibootmgr 8 , 152.Xr efidp 8 , 153.Xr efivar 8 , 154.Xr gpart 8 , 155.Xr uefisign 8 156.Sh HISTORY 157EFI boot support for the ia64 architecture first appeared in 158.Fx 5.0 . 159.Nm 160boot support for amd64 first appeared in 161.Fx 10.1 162and for arm64 in 163.Fx 11.0 . 164.Sh CAVEATS 165EFI environment variables are not supported by 166.Xr loader 8 167or the kernel. 168