xref: /freebsd/share/man/man8/uefi.8 (revision 32100375a661c1e16588ddfa7b90ca8d26cb9786)
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25.\" $FreeBSD$
26.\"
27.Dd May 9, 2020
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 arm Ta Pa /EFI/BOOT/BOOTARM.EFI
73.It arm64 Ta Pa /EFI/BOOT/BOOTAA64.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
91searches partitions of type
92.Li freebsd-ufs
93and
94.Li freebsd-zfs
95for
96.Pa loader.efi .
97The search begins with partitions on the device from which
98.Pa loader.efi
99was loaded, and continues with other available partitions.
100If both
101.Li freebsd-ufs
102and
103.Li freebsd-zfs
104partitions exist on the same device the
105.Li freebsd-zfs
106partition is preferred.
107.It
108.Pa loader.efi
109loads and boots the kernel, as described in
110.Xr loader 8 .
111.El
112.Pp
113The
114.Xr vt 4
115system console is automatically selected when booting via
116.Nm .
117.Sh FILES
118.Bl -tag -width /boot/loader -compact
119.Nm
120bootstrap
121.It Pa /boot/loader.efi
122Final stage bootstrap
123.It Pa /boot/kernel/kernel
124default kernel
125.It Pa /boot/kernel.old/kernel
126typical non-default kernel (optional)
127.El
128.Sh SEE ALSO
129.Xr vt 4 ,
130.Xr boot.config 5 ,
131.Xr msdosfs 5 ,
132.Xr boot 8 ,
133.Xr efibootmgr 8 ,
134.Xr efidp 8 ,
135.Xr efivar 8 ,
136.Xr gpart 8 ,
137.Xr uefisign 8
138.Sh HISTORY
139EFI boot support for the ia64 architecture first appeared in
140.Fx 5.0 .
141.Nm
142boot support for amd64 first appeared in
143.Fx 10.1
144and for arm64 in
145.Fx 11.0 .
146.Sh CAVEATS
147EFI environment variables are not supported by
148.Xr loader 8
149or the kernel.
150