xref: /freebsd/share/man/man8/uefi.8 (revision 9f747dc6dce54e03bb254f9ade85447587c0cf63)

.\" Copyright (c) 2014 The FreeBSD Foundation
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd January 24, 2018
.Dt UEFI 8
.Os
.Sh NAME
.Nm UEFI
.Nd Unified Extensible Firmware Interface bootstrapping procedures
.Sh DESCRIPTION
The
.Nm
Unified Extensible Firmware Interface provides boot- and run-time services
to operating systems.
.Nm
is a replacement for the legacy BIOS on the i386 and amd64 CPU architectures,
and is also used on arm, arm64 and ia64.
.Pp
The UEFI specification is the successor to the Extensible Firmware Interface
(EFI) specification.
The terms are often used interchangeably.
.Pp
The
.Nm
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
.Xr msdosfs 5
FAT file system with a specified file hierarchy.
.Bl -column -offset indent ".Sy Partition Scheme" ".Sy ESP Identifier"
.It Sy "Partition Scheme" Ta Sy "ESP Identifier"
.It GPT Ta C12A7328-F81F-11D2-BA4B-00A0C93EC93B
.It MBR Ta 0xEF
.El
.Pp
The
.Nm
boot process proceeds as follows:
.Bl -enum -offset indent -compact
.It
.Nm
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, the default is
.Pa /EFI/BOOT/BOOTX64.EFI .
The default
.Nm
boot configuration for
.Fx
installs
.Pa boot1.efi
as
.Pa /EFI/BOOT/BOOTX64.EFI .
.It
.Pa boot1.efi
reads boot configuration from
.Pa /boot.config
or
.Pa /boot/config .
Unlike other first-stage boot loaders,
.Pa boot1.efi
passes the configuration to the next stage boot loader and does not
itself act on the contents of the file.
.It
.Pa boot1.efi
searches partitions of type
.Li freebsd-ufs
and
.Li freebsd-zfs
for
.Pa loader.efi .
The search begins with partitions on the device from which
.Pa boot1.efi
was loaded, and continues with other available partitions.
If both
.Li freebsd-ufs
and
.Li freebsd-zfs
partitions exist on the same device the
.Li freebsd-zfs
partition is preferred.
.Pa boot1.efi
then loads and executes
.Pa loader.efi .
.It
.Pa loader.efi
loads and boots the kernel, as described in
.Xr loader 8 .
.El
.Pp
The
.Xr vt 4
system console is automatically selected when booting via
.Nm .
.Sh FILES
.Bl -tag -width /boot/loader -compact
.It Pa /boot/boot1.efi
First stage
.Nm
bootstrap
.It Pa /boot/boot1.efifat
.Xr msdosfs 5
FAT file system image containing
.Pa boot1.efi
for use by
.Xr bsdinstall 8
and the
.Ar bootcode
argument to
.Xr gpart 8 .
.It Pa /boot/loader.efi
Final stage bootstrap
.It Pa /boot/kernel/kernel
default kernel
.It Pa /boot/kernel.old/kernel
typical non-default kernel (optional)
.El
.Sh SEE ALSO
.Xr vt 4 ,
.Xr boot.config 5 ,
.Xr msdosfs 5 ,
.Xr boot 8 ,
.Xr efibootmgr 8 ,
.Xr efidp 8 ,
.Xr efivar 8 ,
.Xr gpart 8 ,
.Xr uefisign 8
.Sh HISTORY
EFI boot support for the ia64 architecture first appeared in
.Fx 5.0 .
.Nm
boot support for amd64 first appeared in
.Fx 10.1
and for arm64 in
.Fx 11.0 .
.Sh CAVEATS
EFI environment variables are not supported by
.Xr loader 8
or the kernel.