Difference between revisions of "Unified Extensible Firmware Interface"

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[[Category:Boot process]]
 
[[Category:Boot process]]
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[[es:Unified Extensible Firmware Interface]]
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[[it:Unified Extensible Firmware Interface]]
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[[ja:Unified Extensible Firmware Interface]]
 
[[ru:Unified Extensible Firmware Interface]]
 
[[ru:Unified Extensible Firmware Interface]]
{{Article summary start}}
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[[zh-hans:Unified Extensible Firmware Interface]]
{{Article summary text|An overview of the Unified Extensible Firmware Interface.}}
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{{Related articles start}}
{{Article summary heading|Overview}}
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{{Related|EFI system partition}}
{{Article summary text|{{Boot process overview}}}}
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{{Related|Arch boot process}}
{{Article summary heading|Related}}
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{{Related|GUID Partition Table}}
{{Article summary wiki|GUID Partition Table}}
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{{Related|Secure Boot}}
{{Article summary wiki|Master Boot Record}}
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{{Related articles end}}
{{Article summary wiki|Arch Boot Process}}
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{{Warning|While the choice to install in UEFI mode is forward looking, early vendor UEFI implementations ''may'' carry more bugs than their BIOS counterparts. It is advised to do a search relating to your particular motherboard model before proceeding.}}
{{Article summary end}}
 
  
'''Unified Extensible Firmware Interface''' (or UEFI for short) is a new type of firmware that was initially designed by Intel (known as EFI then) mainly for its Itanium based systems. It introduces new ways of booting an OS that is distinct from the commonly used "MBR boot code" method followed for BIOS systems. It started as Intel's EFI in versions 1.x and then a group of companies called the UEFI Forum took over its development from which it was called Unified EFI starting with version 2.0 . As of 23 May 2012, UEFI Specification 2.3.1 is the most recent version.
+
The [https://www.uefi.org/ Unified Extensible Firmware Interface] (UEFI or EFI for short) is a new model for the interface between operating systems and firmware. It provides a standard environment for booting an operating system and running pre-boot applications.
  
{{Note|Unless specified as EFI 1.x , EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware. Also unless stated explicitely, these instructions are general and not Mac specific. Some of them may not work or may be different in Macs. Apple's EFI implementation is neither a EFI 1.x version nor UEFI 2.x version but mixes up both. This kind of firmware does not fall under any one UEFI Specification version and therefore it is not a standard UEFI firmware.}}
+
It is distinct from the commonly used "[[Partitioning#Master Boot Record (bootstrap code)|MBR boot code]]" method followed for [[Wikipedia:BIOS|BIOS]] systems. See [[Arch boot process]] for their differences and the boot process using UEFI. To set up UEFI boot loaders, see [[Arch boot process#Boot loader]].
  
== Booting an OS using BIOS ==
+
== UEFI versions ==
  
A BIOS or Basic Input-Output System is the very first program that is executed once the system is switched on. After all the hardware has been initialized and the POST operation has completed, the BIOS executes the first boot code in the first device in the device booting list.  
+
* UEFI started as Intel's EFI in versions 1.x.
 +
* Later, a group of companies called the UEFI Forum took over its development, which renamed it as Unified EFI starting with version 2.0.
 +
* Unless specified as EFI 1.x, EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware.
 +
* Apple's EFI implementation is neither a EFI 1.x version nor UEFI 2.x version but mixes up both. This kind of firmware does not fall under any one (U)EFI specification and therefore is not a standard UEFI firmware. Unless stated explicitly, these instructions are general and some of them may not work or may be different in [[MacBook|Apple Macs]].
  
If the list starts with a CD/DVD drive, then the El-Torito entry in the CD/DVD is executed. This is how bootable CD/DVD works. If the list starts with a HDD, then BIOS executes the very first 440 bytes MBR boot code. The boot code then chainloads or bootstraps a much larger and complex bootloader which then loads the OS.
+
The latest UEFI specification can be found at https://uefi.org/specifications.
  
Basically, the BIOS does not know how to read a partition table or filesystem. All it does is initialize the hardware, then load and run the 440-byte boot code.
+
== UEFI firmware bitness ==
  
=== Multiboot on BIOS ===
+
Under UEFI, every program whether it is an OS loader or a utility (e.g. a memory testing app or recovery tool), should be a EFI application corresponding to the UEFI firmware bitness/architecture.
  
Since very little can be achieved by a program that fits into the 440-byte boot code area, multi-booting using BIOS requires a multi-boot capable bootloader (multi-boot refers to booting multiple operating systems, not to booting a kernel in the Multiboot format specified by the GRUB developers). So usually a common bootloader like [[GRUB]] or [[GRUB2]] or [[Syslinux]] or [[LILO]] would be loaded by the BIOS, and it would load an operating system by either chain-loading or directly loading the kernel.
+
The vast majority of UEFI firmwares, including recent Apple Macs, use x86_64 UEFI firmware. The only known devices that use IA32 (32-bit) UEFI are older (pre 2008) Apple Macs, Intel Atom System-on-Chip systems (as on 2 November 2013)[https://software.intel.com/en-us/blogs/2015/07/22/why-cheap-systems-run-32-bit-uefi-on-x64-systems] and some older Intel server boards that are known to operate on Intel EFI 1.10 firmware.
  
== Booting an OS using UEFI ==
+
An x86_64 UEFI firmware does not include support for launching 32-bit EFI applications (unlike x86_64 Linux and Windows versions which include such support). Therefore the EFI application must be compiled for that specific firmware processor bitness/architecture.
  
UEFI firmware does not support booting through the above mentioned method which is the only way supported by BIOS. UEFI has support for reading both the partition table as well as understanding filesystems.  
+
{{Note|The official ISO does not support booting on 32-bit (IA32) UEFI systems, see [[#Booting 64-bit kernel on 32-bit UEFI]] for available workarounds. The installed system will require using a boot loader that supports IA32 UEFI, for example, [[GRUB]] with the {{ic|i386-efi}} target.}}
  
The commonly used UEFI firmwares support both MBR and GPT partition table. EFI in Apple-Intel Macs are known to support Apple Partition Map also apart from MBR and GPT. Most of the UEFI firmwares have support for accessing FAT12 (floppy disks) , FAT16 and FAT32 filesystems in HDD and ISO9660 (and UDF) in CD/DVDs. EFI in Apple-Intel Macs can access HFS/HFS+ filesystems also apart from the mentioned ones.
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=== Checking the firmware bitness ===
  
UEFI does not launch any boot code in the MBR whether it exists or not. Instead it uses a special partition in the partition table called "EFI SYSTEM PARTITION" in which files required to be launched by the firmware is stored. Each vendor can store its files under <EFI SYSTEM PARTITION>/EFI/<VENDOR NAME>/ folder and can use the firmware or its shell (UEFI shell) to launch the boot program. An EFI System Partition is usually formatted as FAT32.
+
The firmware bitness can be checked from a booted operating system.
  
Under UEFI, every program whether they are OS loaders or some utilities (like memory testing apps) or recovery tools outside the OS, should be a UEFI Application corresponding to the EFI firmware architecture. Most of the UEFI firmware in the market, including recent Apple Macs use x86_64 EFI firmware. Only some older macs use i386 EFI firmware while no non-Apple UEFI system is known to use i386 EFI firmware.
+
==== From Linux ====
  
A x86_64 EFI firmware does not include support for launching 32-bit EFI apps unlike the 64-bit Linux and Windows which include such support. Therefore the bootloader must be compiled for that architecture correctly.
+
On distributions running Linux kernel 4.0 or newer, the UEFI firmware bitness can be found via the sysfs interface. Run:
  
=== Multibooting on UEFI ===
+
$ cat /sys/firmware/efi/fw_platform_size
  
Since each OS or vendor can maintain its own files within the EFI SYSTEM PARTITION without affecting the other, multi-booting using UEFI is just a matter of launching a different UEFI application corresponding to the particular OS's bootloader. This removes the need for relying on chainloading mechanisms of one bootloader to load another to switch OSes.
+
It will return {{ic|64}} for a 64-bit (x86_64) UEFI or {{ic|32}} for a 32-bit (IA32) UEFI. If the file does not exist, then you have not booted in UEFI mode.
  
==== Linux Windows x86_64 UEFI-GPT Multiboot ====
+
==== From macOS ====
  
Windows Vista (SP1+) and 7 pr 8 x86_64 versions support booting natively using UEFI firmware. But for this they need [[GPT]] partitioning of the disk used for UEFI booting. Windows x86_64 versions support either UEFI-GPT booting or BIOS-MBR booting. Windows 32-bit versions support only BIOS-MBR booting. Follow the instructions provided in the forum link given in the references sections as to how to do this. See http://support.microsoft.com/default.aspx?scid=kb;EN-US;2581408 for more info.
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Pre-2008 [[Mac]]s mostly have IA32 EFI firmware while >=2008 Macs have mostly x86_64 EFI. All Macs capable of running Mac OS X Snow Leopard 64-bit Kernel have x86_64 EFI 1.x firmware.
  
This limitation does not exist in Linux Kernel but rather depends on the bootloader used. For the sake of Windows UEFI booting, the Linux bootloader used should also be installed in UEFI-GPT mode if booting from the same disk.
+
To find out the arch of the EFI firmware in a Mac, type the following into the Mac OS X terminal:
  
== Boot Process under UEFI ==
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$ ioreg -l -p IODeviceTree | grep firmware-abi
  
# System switched on - Power On Self Test, or POST process.
+
If the command returns {{ic|EFI32}} then it is IA32 (32-bit) EFI firmware. If it returns {{ic|EFI64}} then it is x86_64 EFI firmware. Most of the Macs do not have UEFI 2.x firmware as Apple's EFI implementation is not fully compliant with UEFI 2.x specification.
# UEFI firmware is loaded.
 
# Firmware reads its Boot Manager to determine which UEFI application to be launched and from where (ie. from which disk and partition).
 
# Firmware launches the UEFI application from the FAT32 formatted UEFISYS partition as defined in the boot entry in the firmware's boot manager.
 
# UEFI application may launch another application (in case of UEFI Shell or a boot manager like rEFInd) or the kernel and initramfs (in case of a bootloader like GRUB2) depending on how the UEFI application was configured.
 
  
== Detecting UEFI Firmware Arch ==
+
==== From Microsoft Windows ====
  
If you have a non-mac UEFI system, then you have a x86_64 (aka 64-bit) UEFI 2.x firmware.
+
64-bit versions of Windows do not support booting on a 32-bit UEFI. So, if you have a 32-bit version of Windows booted in UEFI mode, you have a 32-bit UEFI.
  
Some of the known x86_64 UEFI 2.x firmwares are Phoenix SecureCore Tiano, AMI Aptio, Insyde H2O.
+
To check the bitness run {{ic|msinfo32.exe}}. In the ''System Summary'' section look at the values of "System Type" and "BIOS mode".
  
Some of the known systems using these firmwares are Asus EZ Mode BIOS (in Sandy Bridge P67 and H67 motherboards), MSI ClickBIOS, HP EliteBooks, Sony Vaio Z series, many Intel Server and Desktop motherboards
+
For a 64-bit Windows on a 64-bit UEFI it will be {{ic|System Type: x64-based PC}} and {{ic|BIOS mode: UEFI}}, for a 32-bit Windows on a 32-bit UEFI - {{ic|System Type: x86-based PC}} and {{ic|BIOS mode: UEFI}}. If the "BIOS mode" is not {{ic|UEFI}}, then Windows is not installed in UEFI mode.
  
 +
== Linux kernel config options for UEFI ==
  
Pre-2008 Macs mostly have i386-efi firmware while >=2008 Macs have mostly x86_64-efi. All macs capable of running Mac OS X Snow Leopard 64-bit Kernel have x86_64 EFI 1.x firmware.
+
The required Linux Kernel configuration options[https://www.kernel.org/doc/Documentation/x86/x86_64/uefi.txt] for UEFI systems are:
  
To find out the arch of the efi firmware in a Mac, boot into Mac OS X and type the following command
+
CONFIG_RELOCATABLE=y
 +
CONFIG_EFI=y
 +
CONFIG_EFI_STUB=y
 +
CONFIG_X86_SYSFB=y
 +
CONFIG_FB_SIMPLE=y
 +
CONFIG_FRAMEBUFFER_CONSOLE=y
  
<pre>
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UEFI Runtime Variables Support ('''efivarfs''' filesystem - {{ic|/sys/firmware/efi/efivars}}). This option is important as this is required to manipulate UEFI runtime variables using tools like {{ic|/usr/bin/efibootmgr}}. The below config option has been added in kernel 3.10 and above.
ioreg -l -p IODeviceTree | grep firmware-abi
 
</pre>
 
  
If the command returns EFI32 the it is i386 EFI 1.x firmware. If it returns EFI64 then it is x86_64 EFI 1.x firmware. Macs do not have UEFI 2.x firmware as Apple's efi implementation is not fully compliant with UEFI Specification.
+
CONFIG_EFIVAR_FS=y
  
== UEFI Support in Linux Kernel ==
+
UEFI Runtime Variables Support (old '''efivars sysfs''' interface - {{ic|/sys/firmware/efi/vars}}). This option should be disabled to prevent any potential issues with both efivarfs and sysfs-efivars enabled.
  
=== Linux Kernel config options for UEFI ===
+
CONFIG_EFI_VARS=n
  
The required Linux Kernel configuration options for UEFI systems are :
+
[[GUID Partition Table]] (GPT) config option - mandatory for UEFI support
  
  CONFIG_EFI=y
+
  CONFIG_EFI_PARTITION=y
  CONFIG_EFI_STUB=y
+
 
CONFIG_RELOCATABLE=y
+
EFI mixed-mode support - to boot a x64_64 kernel on a IA32 UEFI.
CONFIG_FB_EFI=y
+
 
CONFIG_FRAMEBUFFER_CONSOLE=y
+
  CONFIG_EFI_MIXED=y
 +
 
 +
{{Note|All of the above options are enabled in Arch Linux [[kernels]] in the official repositories.}}
 +
 
 +
== UEFI variables ==
  
UEFI Runtime Variables/Services Support - 'efivars' kernel module . This option is important as this is required to manipulate UEFI Runtime Variables using tools like '''efibootmgr'''.
+
UEFI defines variables through which an operating system can interact with the firmware. UEFI boot variables are used by the boot loader and used by the OS only for early system start-up. UEFI runtime variables allow an OS to manage certain settings of the firmware like the UEFI boot manager or managing the keys for UEFI Secure Boot protocol etc. You can get the list using:
 
 
CONFIG_EFI_VARS=m
 
  
{{Note| This option is compiled as module in Arch core/testing kernel.}}
+
$ efivar --list
  
{{Note|For Linux to access UEFI Runtime Services, the UEFI Firmware processor architecture and the Linux kernel processor architecture must match. This is independent of the bootloader used.}}
+
=== UEFI variables support in Linux kernel ===
  
{{Note|If the UEFI Firmware arch and Linux Kernel arch are different, then the "'''noefi'''" kernel parameter must be used to avoid the kernel panic and boot successfully. The "noefi" option instructs the kernel not to access the UEFI Runtime Services.}}
+
Linux kernel exposes UEFI variables data to userspace via '''efivarfs''' ('''EFI''' '''VAR'''iable '''F'''ile'''S'''ystem) interface ({{ic|CONFIG_EFIVAR_FS}}) - mounted using {{ic|efivarfs}} kernel module at {{ic|/sys/firmware/efi/efivars}} - it has no maximum per-variable size limitation and supports UEFI Secure Boot variables. Introduced in kernel 3.8.
  
GUID Partition Table [[GPT]] config option - mandatory for UEFI support
+
=== Requirements for UEFI variable support ===
  
CONFIG_EFI_PARTITION=y
+
# Kernel should be booted in UEFI mode via [[EFISTUB]] (optionally using a [[boot manager]]) or by a UEFI [[boot loader]] (using either the EFI handover protocol or the UEFI LoadImage function), not via BIOS or CSM, or Apple's Boot Camp which is also a CSM.
 +
# EFI Runtime Services support should be present in the kernel ({{ic|1=CONFIG_EFI=y}}, check if present with {{ic|zgrep CONFIG_EFI /proc/config.gz}}).
 +
# EFI Runtime Services in the kernel SHOULD NOT be disabled via kernel cmdline, i.e. {{ic|noefi}} kernel parameter SHOULD NOT be used.
 +
# {{ic|efivarfs}} filesystem should be mounted at {{ic|/sys/firmware/efi/efivars}}, otherwise follow [[#Mount efivarfs]] section below.
 +
# {{ic|efivar}} should list (option {{ic|-l}}/{{ic|--list}}) the UEFI variables without any error.
  
{{Note|All of the above options are required to boot Linux via UEFI, and are enabled in Archlinux kernels in official repos.}}
+
If UEFI Variables support does not work even after the above conditions are satisfied, try the below workarounds:
  
Retrieved from http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob_plain;f=Documentation/x86/x86_64/uefi.txt;hb=HEAD .
+
# If any userspace tool is unable to modify UEFI variable data, check for existence of {{ic|/sys/firmware/efi/efivars/dump-*}} files. If they exist, delete them, reboot and retry again.
 +
# If the above step does not fix the issue, try booting with {{ic|efi_no_storage_paranoia}} kernel parameter to disable kernel UEFI variable storage space check that may prevent writing/modification of UEFI variables.
  
== UEFI Variables Support ==
+
{{Warning|{{ic|efi_no_storage_paranoia}} should only be used when needed and should not be left as a normal boot option. The effect of this kernel command line parameter turns off a safeguard that was put in place to help avoid the bricking of machines when the NVRAM gets too full. See {{Bug|34641}} for more information.}}
  
UEFI defines variables through which an operating system can interact with the firmware. UEFI Boot Variables are used by the boot-loader and used by the OS only for early system start-up. UEFI Runtime Variables allow an OS to manage certain settings of the firmware like the UEFI Boot Manager or managing the keys for UEFI Secure Boot Protocol etc.
+
==== Mount efivarfs ====
  
{{Note|The below steps will not work if the system has been booted in BIOS mode and will not work if the UEFI processor architecture does not match the kernel one, i.e. x86_64 UEFI + ix86 32-bit Kernel and vice-versa config will not work. This is true only for efivars kernel module and efibootmgr step. The other steps (ie. upto setting up <UEFISYS>/efi/arch/grub.{efi,cfg} ) can be done even in BIOS/Legacy boot mode.}}
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If {{ic|efivarfs}} is not automatically mounted at {{ic|/sys/firmware/efi/efivars}} by [[systemd]] during boot, then you need to manually mount it to expose UEFI variables to [[#Userspace tools|userspace tools]] like ''efibootmgr'':
  
Access to UEFI Runtime services is provided by "efivars" kernel module which is enabled through the {{ic|<nowiki>CONFIG_EFI_VAR=m</nowiki>}} kernel config option. This module once loaded exposes the variables under the directory {{ic|/sys/firnware/efi/vars}}. One way to check whether the system has booted in UEFI boot mode is to load the "efivars" kernel module and check for the existence of {{ic|/sys/firnware/efi/vars}} directory with contents similar to :
+
# mount -t efivarfs efivarfs /sys/firmware/efi/efivars
  
Sample output (x86_64-UEFI 2.3.1 in x86_64 Kernel):
+
{{Note|The above command should be run both '''outside''' ('''before''') and '''inside''' the [[chroot]], if any.}}
 
# ls -1 /sys/firmware/efi/vars/
 
Boot0000-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
BootCurrent-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
BootOptionSupport-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
BootOrder-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
ConIn-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
ConInDev-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
ConOut-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
ConOutDev-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
ErrOutDev-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
Lang-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
LangCodes-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
MTC-eb704011-1402-11d3-8e77-00a0c969723b/
 
MemoryTypeInformation-4c19049f-4137-4dd3-9c10-8b97a83ffdfa/
 
PlatformLang-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
PlatformLangCodes-8be4df61-93ca-11d2-aa0d-00e098032b8c/
 
RTC-378d7b65-8da9-4773-b6e4-a47826a833e1/
 
del_var
 
new_var
 
  
The UEFI Runtime Variables will not be exposed to the OS if you have used "noefi" kernel parameter in the boot-loader menu. This parameter instructs the kernel to completely ignore UEFI Runtime Services.
+
See [https://www.kernel.org/doc/Documentation/filesystems/efivarfs.txt efivarfs.txt] for kernel documentation.
  
=== Userspace Tools ===
+
=== Userspace tools ===
  
 
There are few tools that can access/modify the UEFI variables, namely
 
There are few tools that can access/modify the UEFI variables, namely
  
# efibootmgr - Used to create/modify boot entries in the UEFI Boot Manager - {{Pkg|efibootmgr}} or {{AUR|efibootmgr-git}}
+
* {{App|efivar|Library and Tool to manipulate UEFI variables (used by efibootmgr)|https://github.com/rhboot/efivar|{{Pkg|efivar}}, {{AUR|efivar-git}}}}
# uefivars - simply dumps the variables - {{AUR|uefivars-git}} - uses efibootmgr library
+
* {{App|efibootmgr|Tool to manipulate UEFI Firmware Boot Manager Settings|https://github.com/rhboot/efibootmgr|{{Pkg|efibootmgr}}}}
# Ubuntu's Firmware Test Suite - fwts - {{AUR|fwts-git}} - uefidump command - {{ic|fwts uefidump}}  
+
* {{App|uefivars|Dumps list of UEFI variables with some additional PCI related info (uses efibootmgr code internally)|https://github.com/fpmurphy/Various/tree/master/uefivars-2.0|{{AUR|uefivars-git}}}}
 +
* {{App|efitools|Tools for manipulating UEFI secure boot platforms|https://git.kernel.org/pub/scm/linux/kernel/git/jejb/efitools.git|{{Pkg|efitools}}}}
 +
* {{App|Ubuntu's Firmware Test Suite|Test suite that performs sanity checks on Intel/AMD PC firmware|https://wiki.ubuntu.com/FirmwareTestSuite/|{{AUR|fwts-git}}}}
 +
 
 +
==== efibootmgr ====
 +
 
 +
You will have to [[install]] the {{Pkg|efibootmgr}} package.
  
=== Non-Mac UEFI systems ===
+
{{Note|
 +
* If ''efibootmgr'' does not work on your system, you can reboot into [[#UEFI Shell]] and use {{ic|bcfg}} to create a boot entry for the bootloader.
 +
* If you are unable to use {{ic|efibootmgr}}, some UEFI firmwares allow users to directly manage UEFI boot entries from within its boot-time interface. For example, some firmwares have an "Add New Boot Option" choice which enables you to select a local EFI system partition and manually enter the EFI application location e.g. {{ic|\EFI\refind\refind_x64.efi}}.
 +
* The below commands use [[rEFInd]] boot manager as example.
 +
}}
  
==== efibootmgr ====
+
To add a new boot option using ''efibootmgr'' you need to know three things:
 +
 
 +
# The disk containing the [[EFI system partition]] (ESP). E.g.: {{ic|/dev/sda}}, {{ic|/dev/nvme0n1}}.
 +
# The partition number of the ESP on that disk. The {{ic|''Y''}} in {{ic|/dev/sda''Y''}} or {{ic|/dev/nvme0n1p''Y''}}.
 +
# The path to the EFI application (relative to the root of the ESP)
 +
 
 +
For example, if you want to add a boot option for {{ic|/efi/EFI/refind/refind_x64.efi}} where {{ic|/efi}} is the mount point of the ESP, run
 +
 
 +
{{hc|$ findmnt /efi|2=
 +
TARGET SOURCE    FSTYPE OPTIONS
 +
/efi  /dev/sda1 vfat  rw,flush,tz=UTC
 +
}}
 +
 
 +
In this example, this indicates that the ESP is on disk {{ic|/dev/sda}} and has partition number 1. The path to the EFI application relative to the root of the ESP is {{ic|/EFI/refind/refind_x64.efi}}. So you would create the boot entry as follows:
 +
 
 +
# efibootmgr --create --disk /dev/sda --part 1 --loader /EFI/refind/refind_x64.efi --label "rEFInd Boot Manager" --verbose
 +
 
 +
{{Accuracy|{{ic|/dev/nvme0n1p1}} is a partition not a disk, the partition number should be specified using the {{ic|--part}} option.}}
 +
 
 +
# efibootmgr --create --disk /dev/nvme0n1p1 --loader /EFI/refind/refind_x64.efi --label "rEFINd Boot Manager" --verbose
 +
 
 +
See {{man|8|efibootmgr}} or [https://raw.githubusercontent.com/rhinstaller/efibootmgr/master/README efibootmgr README] for more info.
 +
 
 +
{{Note|UEFI uses backward slash {{ic|\}} as path separator but ''efibootmgr'' automatically converts UNIX-style {{ic|/}} path separators.}}
  
{{Warning|Using {{ic|efibootmgr}} in Apple Macs will brick the firmware and may need reflash of the motherboard ROM. There have been bug reports regarding this in Ubuntu/Launchpad bug tracker. Use bless command alone in case of Macs. Experimental "bless" utility for Linux by Fedora developers - {{AUR|mactel-boot}}.}}
+
== UEFI Shell ==
  
{{Note|{{ic|efibootmgr}} command will work only if you have booted the system in UEFI mode itself, since it '''requires access to UEFI Runtime Variables''' which are '''available only in UEFI boot mode''' (with "noefi" kernel parameter NOT being used). Otherwise the message {{ic|Fatal: Couldn't open either sysfs or procfs directories for accessing EFI variables}} is shown.}}
+
The UEFI Shell is a shell/terminal for the firmware which allows launching EFI applications which include UEFI bootloaders. Apart from that, the shell can also be used to obtain various other information about the system or the firmware like memory map (memmap), modifying boot manager variables (bcfg), running partitioning programs (diskpart), loading UEFI drivers, editing text files (edit), hexedit etc.
  
Initially the user may be required to manually launch the boot-loader from the firmware itself (using maybe the UEFI Shell) if the UEFI boot-loader was installed when the system is booted in BIOS mode. Then {{ic|efibootmgr}} should be run to make the UEFI boot-loader entry as the default entry in the UEFI Boot Manager.
+
=== Obtaining UEFI Shell ===
  
To use efibootmgr, first load the 'efivars' kernel module:
+
You can download a BSD licensed UEFI Shell from Intel's TianoCore UDK/EDK2 project:
  
# modprobe efivars
+
* [[AUR]] package {{AUR|uefi-shell-git}} (recommended) - provides x86_64 Shell for x86_64 (64-bit) UEFI and IA32 Shell for IA32 (32-bit) UEFI - compiled directly from latest TianoCore EDK2 source.
 +
* There are copies of Shell v1 and Shell v2 in the EFI directory on the Arch install media image.
 +
* [https://github.com/tianocore/edk2/releases/latest/download/ShellBinPkg.zip Precompiled UEFI Shell v2 binaries] (the binary package was moved from its original location in the source tree to the GitHub release assets, as laid out [https://lists.01.org/pipermail/edk2-devel/2019-April/thread.html#38524 here]).
 +
* [https://github.com/tianocore/edk2/tree/UDK2018/EdkShellBinPkg Precompiled UEFI Shell v1 binaries] (not updated anymore upstream as of Jan 10, 2014).
 +
* [https://drive.google.com/uc?export=download&id=1OBXYj6MEs7VAZbYnjD9FxOYcZYIQoq36 Precompiled UEFI Shell v2 binary with bcfg modified to work with UEFI pre-2.3 firmware] - from Clover EFI bootloader.
  
If you get '''no such device found''' error for this command, that means you have not booted in UEFI mode or due to some reason the kernel is unable to access UEFI Runtime Variables (noefi?).
+
Shell v2 works best in UEFI 2.3+ systems and is recommended over Shell v1 in those systems. Shell v1 should work in all UEFI systems irrespective of the spec. version the firmware follows. More info at [https://github.com/tianocore/tianocore.github.io/wiki/ShellPkg ShellPkg] and [https://edk2-devel.narkive.com/zCN4CEnb/inclusion-of-uefi-shell-in-linux-distro-iso this mail].
  
Verify whether there are files in ''/sys/firmware/efi/vars/'' directory. This directory and its contents are created by "efivars" kernel module and it will exist only if you have booted in UEFI mode, without the "noefi" kernel parameter.
+
=== Launching UEFI Shell ===
  
If ''/sys/firmware/efi/vars/'' directory is empty or does not exist, then {{ic|efibootmgr}} command will not work. If you are unable to make the ISO/CD/DVD/USB boot in UEFI mode try https://gitorious.org/tianocore_uefi_duet_builds/pages/Linux_Windows_BIOS_UEFI_boot_USB.
+
Few Asus and other AMI Aptio x86_64 UEFI firmware based motherboards (from Sandy Bridge onwards) provide an option called {{ic|"Launch EFI Shell from filesystem device"}} . For those motherboards, download the x86_64 UEFI Shell and copy it to your EFI system partition as {{ic|<EFI_SYSTEM_PARTITION>/shellx64.efi}}.
  
{{Note| The below commands use grub-efi-x86_64 boot-loader as example.}}
+
Systems with Phoenix SecureCore Tiano UEFI firmware are known to have embedded UEFI Shell which can be launched using either {{ic|F6}}, {{ic|F11}} or {{ic|F12}} key.
  
Assume the boot-loader file to be launched is {{ic|/boot/efi/efi/arch_grub/grubx64.efi}}. {{ic|/boot/efi/efi/arch_grub/grubx64.efi}} can be split up as {{ic|/boot/efi}} and {{ic|/efi/arch_grub/grubx64.efi}}, wherein {{ic|/boot/efi}} is the mountpoint of the UEFI System Partition, which is assumed to be /dev/sdXY (here X and Y are just placeholders for the actual values - eg:- in /dev/sda1 , X=a Y=1).
+
{{Note|If you are unable to launch UEFI Shell from the firmware directly using any of the above mentioned methods, create a [[FAT32]] USB pen drive with {{ic|Shell.efi}} copied as {{ic|(USB)/EFI/BOOT/BOOTx64.EFI}}. This USB should come up in the firmware boot menu. Launching this option will launch the UEFI Shell for you.}}
  
To determine the actual device path for the UEFI System Partition, try :
+
=== Important UEFI Shell commands ===
  
# cat /proc/self/mounts | grep /boot/efi | awk '{print $1}'
+
UEFI Shell commands usually support {{ic|-b}} option which makes output pause after each page. Run {{ic|help -b}} to list available internal commands. Available commands are either built into the shell or discrete EFI applications.
/dev/sdXY
 
  
Then create the boot entry using efibootmgr as follows :
+
For more info see [https://software.intel.com/en-us/articles/efi-shells-and-scripting/ Intel Scripting Guide 2008] and [https://software.intel.com/en-us/articles/uefi-shell Intel "Course" 2011].
  
# efibootmgr --create --gpt --disk /dev/sdX --part Y --write-signature --label "Arch Linux (GRUB2)" --loader '\EFI\arch_grub\grubx64.efi'
+
==== bcfg ====
  
In the above command {{ic|/boot/efi/efi/arch_grub/grubx64.efi}} translates to {{ic|/boot/efi}} and {{ic|/efi/arch_grub/grubx64.efi}} which in turn translate to drive {{ic|/dev/sdX}} -> partition Y -> file {{ic|/EFI/arch_grub/grubx64.efi}}.
+
{{ic|bcfg}} modifies the UEFI NVRAM entries which allows the user to change the boot entries or driver options. This command is described in detail in page 83 (Section 5.3) of the [https://www.uefi.org/sites/default/files/resources/UEFI_Shell_Spec_2_0.pdf UEFI Shell Specification 2.0] document.
  
UEFI uses backward slash as path separator (similar to Windows paths).
+
{{Note|
 +
* Try {{ic|bcfg}} only if {{ic|efibootmgr}} fails to create working boot entries on your system.
 +
* UEFI Shell v1 official binary does not support {{ic|bcfg}} command. See [[#Obtaining UEFI Shell]] for a modified UEFI Shell v2 binary which may work in UEFI pre-2.3 firmwares.
 +
}}
  
The 'label' is the name of the menu entry shown in the UEFI boot menu. This name is user's choice and does not affect the booting of the system. More info can be obtained from [http://linux.dell.com/cgi-bin/gitweb/gitweb.cgi?p=efibootmgr.git;a=blob_plain;f=README;hb=HEAD efibootmgr GIT README] .
+
To dump a list of current boot entries:
  
FAT32 filesystem is case-insensitive since it does not use UTF-8 encoding by default. In that case the firmware uses capital 'EFI' instead of small 'efi', therefore using {{ic|\EFI\arch_grub\grubx64.efi}} or {{ic|\efi\arch_grub\grubx64.efi}} does not matter (this will change if the filesystem encoding is UTF-8).
+
Shell> bcfg boot dump -v
  
== Linux Bootloaders for UEFI ==
+
To add a boot menu entry for rEFInd (for example) as 4th (numbering starts from zero) option in the boot menu:
  
See [[UEFI Bootloaders]].
+
Shell> bcfg boot add 3 FS0:\EFI\refind\refind_x64.efi "rEFInd"
  
== Create an UEFI System Partition in Linux ==
+
where {{ic|FS0:}} is the mapping corresponding to the EFI system partition and {{ic|FS0:\EFI\refind\refind_x64.efi}} is the file to be launched.
  
{{Note|The UEFISYS partition can be of any size supported by FAT32 filesystem. According to Microsoft Documentation, the minimum partition/volume size for FAT32 is 512 MiB. Therefore it is recommended for UEFISYS partition to be atleast 512 MiB. Higher partition sizes are fine, especially if you use multiple UEFI bootloaders, or multiple OSes booting via UEFI, so that there is enough space to hold all the related files. If you are using Linux EFISTUB booting, then you need to make sure there is adequate space available for keeping the Kernel and Initramfs files in the UEFISYS partition.}}
+
To add an entry to boot directly into your system without a bootloader, configure a boot option using your kernel as an [[EFISTUB#UEFI_Shell|EFISTUB]]:
  
=== For GPT partitioned disks ===
+
Shell> bcfg boot add '''N''' fs'''V''':\vmlinuz-linux "Arch Linux"
Two choices:
+
Shell> bcfg boot -opt '''N''' "root='''/dev/sdX#''' initrd=\initramfs-linux.img"
* Using GNU Parted/GParted: Create a FAT32 partition. Set "boot" flag on for that partition.
 
* Using GPT fdisk (aka gdisk): Create a partition with gdisk type code "EF00". Then format that partition as FAT32 using {{ic|mkfs.vfat -F32 /dev/<THAT_PARTITION>}}
 
  
{{Note|Setting "boot" flag in parted in a MBR partition marks that partition as active, while the same "boot" flag in a GPT partition marks that partition as "UEFI System Partition".}}
+
where {{ic|N}} is the priority, {{ic|V}} is the volume number of your EFI system partition, and {{ic|/dev/sdX#}} is your root partition.
  
{{Warning|Do not use util-linux fdisk, cfdisk or sfdisk to change the type codes in a GPT disk. Similarly do not use gptfdisk gdisk, cgdisk or sgdisk on a MBR disk, it will be automatically converted to GPT (no data loss will occur, but the system will fail to boot).}}
+
To remove the 4th boot option:
  
=== For MBR partitioned disks ===
+
Shell> bcfg boot rm 3
Two choices:
 
* Using GNU Parted/GParted: Create FAT32 partition. Change the type code of that partition to 0xEF using fdisk, cfdisk or sfdisk.
 
* Using fdisk: Create a partition with partition type 0xEF and format it as FAT32 using {{ic|mkfs.vfat -F32 /dev/<THAT_PARTITION>}}
 
  
{{Note|It is recommended to use always GPT for UEFI boot as some UEFI firmwares do not allow UEFI-MBR boot.}}
+
To move the boot option #3 to #0 (i.e. 1st or the default entry in the UEFI Boot menu):
  
== UEFI Shell ==
+
Shell> bcfg boot mv 3 0
 +
 
 +
For bcfg help text:
 +
 
 +
Shell> help bcfg -v -b
 +
 
 +
or:
 +
 
 +
Shell> bcfg -? -v -b
 +
 
 +
==== map ====
 +
 
 +
{{ic|map}} displays a list of device mappings i.e. the names of available file systems ({{ic|FS0}}) and storage devices ({{ic|blk0}}).
  
The UEFI Shell is a shell/terminal for the firmware which allows launching uefi applications which include uefi bootloaders. Apart from that, the shell can also be used to obtain various other information about the system or the firmware like memory map (memmap), modifying boot manager variables (bcfg), running partitioning programs (diskpart), loading uefi drivers, editing text files (edit), hexedit etc.
+
Before running file system commands such as {{ic|cd}} or {{ic|ls}}, you need to change the shell to the appropriate file system by typing its name:
  
=== UEFI Shell download links ===
+
Shell> FS0:
 +
FS0:\> cd EFI/
  
You can download a BSD licensed UEFI Shell from Intel's Tianocore UDK/EDK2 Sourceforge.net project.
+
==== edit ====
  
* [https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2/ShellBinPkg/UefiShell/X64/Shell.efi x86_64 UEFI Shell 2.0 (Beta)]
+
{{ic|edit}} provides a basic text editor with an interface similar to nano, but slightly less functional. It handles UTF-8 encoding and takes care or LF vs CRLF line endings.
* [https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2/EdkShellBinPkg/FullShell/X64/Shell_Full.efi x86_64 UEFI Shell 1.0 (Old)]
 
* [https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2/ShellBinPkg/UefiShell/Ia32/Shell.efi i386 UEFI Shell 2.0 (Beta)]
 
* [https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2/EdkShellBinPkg/FullShell/Ia32/Shell_Full.efi i386 UEFI Shell 1.0 (Old)]
 
  
Shell 2.0 works only in UEFI 2.3+ systems and is recommended over Shell 1.0 in those systems. Shell 1.0 should work in all UEFI systems irrespective of the spec. version the firmware follows. More info at [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=ShellPkg ShellPkg] and [http://sourceforge.net/mailarchive/message.php?msg_id=28690732 this mail]
+
For example, to edit rEFInd's {{ic|refind.conf}} in the EFI system partition ({{ic|FS0:}} in the firmware),
  
=== Launching UEFI Shell ===
+
Shell> edit FS0:\EFI\refind\refind.conf
  
Few Asus and other AMI Aptio x86_64 UEFI firmware based motherboards (from Sandy Bridge onwards) provide an option called {{ic|"Launch EFI Shell from filesystem device"}} . For those motherboards, download the x86_64 UEFI Shell and copy it to your UEFI SYSTEM PARTITION as {{ic|<UEFI_SYSTEM_PARTITION>/shellx64.efi}} (mostly {{ic|/boot/efi/shellx64.efi}}) .
+
Type {{ic|Ctrl-E}} for help.
  
Systems with Phoenix SecureCore Tiano UEFI firmware are known to have embedded UEFI Shell which can be launched using either F6, F11 or F12 key.
+
== UEFI drivers ==
  
{{Note|If you are unable to launch UEFI Shell from the firmware directly using any of the above mentioned methods, create a FAT32 USB pen drive with Shell.efi copied as (USB)/efi/boot/bootx64.efi . This USB should come up in the firmware boot menu. Launching this option will launch the UEFI Shell for you.}}
+
{{Expansion|Explain what are and how to use UEFI drivers.}}
  
=== Important UEFI Shell Commands ===  
+
== UEFI bootable media ==
  
More info at http://software.intel.com/en-us/articles/efi-shells-and-scripting/
+
=== Create UEFI bootable USB from ISO ===
  
==== bcfg ====
+
Follow [[USB flash installation media#BIOS and UEFI bootable USB]].
  
BCFG command is used to modify the UEFI NVRAM entries, which allow the user to change the boot entries or driver options. This command is described in detail in page 83 (Section 5.3) of "UEFI Shell Specification 2.0" pdf document.
+
=== Remove UEFI boot support from optical media ===
  
{{Note| Users are recommended to try {{ic|bcfg}} only if {{ic|efibootmgr}} fails to create working boot entries in their system.}}
+
{{Note|This section mentions removing UEFI boot support from a '''CD/DVD only''' (Optical Media), not from a USB flash drive.}}
  
{{Note| UEFI Shell 1.0 does not support {{ic|bcfg}} command.}}
+
Most of the 32-bit EFI Macs and some 64-bit EFI Macs refuse to boot from a UEFI(X64)+BIOS bootable CD/DVD. If one wishes to proceed with the installation using optical media, it might be necessary to remove UEFI support first.
  
To dump a list of current boot entries -
+
* Mount the official installation media and obtain the {{ic|archisolabel}} as shown in the previous section.
  
  Shell> bcfg boot dump -v
+
  # mount -o loop ''input.iso'' /mnt/iso
  
To add a boot menu entry for grub2's grubx64.efi (for example) as 4th (numbeering starts from zero) option in the boot menu
+
* Then rebuild the ISO, excluding the UEFI optical media booting support, using {{ic|xorriso}} from {{pkg|libisoburn}}. Be sure to set the correct archisolabel, e.g. "ARCH_201411" or similar:
  
Shell> bcfg boot add 3 fs0:\EFI\arch\grubx64.efi "Arch Linux (GRUB2)"
+
{{bc|1=
 +
$ xorriso -as mkisofs -iso-level 3 \
 +
    -full-iso9660-filenames\
 +
    -volid "''archisolabel''" \
 +
    -appid "Arch Linux CD" \
 +
    -publisher "Arch Linux <https://www.archlinux.org>" \
 +
    -preparer "prepared by $USER" \
 +
    -eltorito-boot isolinux/isolinux.bin \
 +
    -eltorito-catalog isolinux/boot.cat \
 +
    -no-emul-boot -boot-load-size 4 -boot-info-table \
 +
    -isohybrid-mbr "/mnt/iso/isolinux/isohdpfx.bin" \
 +
    -output ''output.iso'' /mnt/iso/
 +
}}
  
where fs0: is the mapping corresponding to the UEFI System Partition and \EFI\arch\grubx64.efi is the file to be launched.
+
* Burn {{ic|''output.iso''}} to optical media and proceed with installation normally.
  
To remove the 4th boot option
+
=== Booting 64-bit kernel on 32-bit UEFI ===
  
Shell> bcfg boot rm 3
+
Official ISO ([[Archiso]]) does not support booting on 32-bit (IA32) UEFI systems ({{Bug|53182}}) since it uses EFISTUB (via [[systemd-boot]] boot manager for menu) for booting the kernel in UEFI mode. To boot a 64-bit kernel with 32-bit UEFI you have to use a boot loader that does not rely on EFI boot stub for launching kernels.
  
To move the boot option #3 to #0 (i.e. 1st or the default entry in the UEFI Boot menu)
+
{{Tip|[[Archboot]] iso supports booting on 32-bit (IA32) UEFI systems.}}
  
Shell> bcfg boot mv 3 0
+
==== Using GRUB ====
  
For bcfg help text
+
This section describes how to setup [[GRUB]] as the USB's UEFI bootloader.
  
Shell> help bcfg -v -b
+
* [[USB flash installation media#Using_manual_formatting|Create an editable USB Flash Installation]]. Since we are going to use GRUB, you only need to follow the steps up until the {{ic|syslinux}} part
  
or
+
* [[GRUB/Tips and tricks#GRUB standalone|Create a GRUB standalone image]] for 32-bit UEFI systems:
  
  Shell> bcfg -? -v -b
+
  # echo 'configfile ${cmdpath}/grub.cfg' > /tmp/grub.cfg
 +
# grub-mkstandalone -d /usr/lib/grub/i386-efi -O i386-efi --modules="part_gpt part_msdos" --locales="en@quot" --themes="" -o "''/mnt/usb/''EFI/boot/bootia32.efi" "boot/grub/grub.cfg=/tmp/grub.cfg" -v
  
==== edit ====
+
* Create {{ic|''/mnt/usb''/EFI/boot/grub.cfg}} with the following contents (replace {{ic|ARCH_YYYYMM}} with the required archiso label e.g. {{ic|ARCH_201507}}):
  
EDIT command provides a basic text editor with an interface similar to nano text editor, but slightly less functional. It handles UTF-8 encoding and takes care or LF vs CRLF line endings.
+
{{Tip|
 +
* The archiso label can be aquired from the ''.iso'' file with {{ic|isoinfo}} from {{Pkg|cdrtools}} or {{ic|iso-info}} from {{Pkg|libcdio}}.
 +
* The given configuration entries can also be entered inside a [[GRUB#Using_the_command_shell|GRUB command-shell]].
 +
}}
  
To edit, for example grub2's grub.cfg in the UEFI System Partition (fs0: in the firmware)
+
For the official ISO:
  
Shell> fs0:
+
{{hc|''/mnt/usb''/EFI/boot/grub.cfg|2=
FS0:\> cd \efi\grub
+
insmod part_gpt
FS0:\efi\grub\> edit grub.cfg
+
insmod part_msdos
 +
insmod fat
  
== Hardware Compatibility ==
+
insmod efi_gop
 +
insmod efi_uga
 +
insmod video_bochs
 +
insmod video_cirrus
  
Main page [[HCL/Firmwares/UEFI]]
+
insmod font
  
 +
if loadfont "${prefix}/fonts/unicode.pf2" ; then
 +
    insmod gfxterm
 +
    set gfxmode="1024x768x32;auto"
 +
    terminal_input console
 +
    terminal_output gfxterm
 +
fi
  
== Create UEFI bootable USB from ISO ==
+
menuentry "Arch Linux archiso x86_64 UEFI USB" {
 +
    set gfxpayload=keep
 +
    search --no-floppy --set=root --label ''ARCH_YYYYMM''
 +
    linux /arch/boot/x86_64/vmlinuz archisobasedir=arch archisolabel=''ARCH_YYYYMM'' add_efi_memmap
 +
    initrd /arch/boot/intel_ucode.img /arch/boot/x86_64/archiso.img
 +
}
 +
}}
  
{{Note|dd'ing the ISO (isohybrid method) to the USB drive will not work for UEFI boot.}}
+
Durring installation, in the [[Installation guide#Boot loader|boot loader installation step]], [[GRUB#Installation_2|install GRUB]] using the option {{ic|1=--target=i386-efi}}.
  
=== Archiso ===
+
== Testing UEFI in systems without native support ==
  
1. Create a directory {{ic|/tmp/archiso}} and extract the archiso file contents to it.
+
=== OVMF for virtual machines ===
  
2. Create a directory {{ic|/tmp/archiso_efiboot}} and extract {{ic|/tmp/archiso/EFI/archiso/efiboot.img}} to it using {{ic|7z}} command from {{Pkg|p7zip}} package.
+
[https://tianocore.github.io/ovmf/ OVMF] is a TianoCore project to enable UEFI support for Virtual Machines. OVMF contains a sample UEFI firmware and a separate non-volatile variable store for QEMU.
  
3. Run the below commands:
+
You can install {{pkg|ovmf}} from the extra repository.
  
# mkdir -p /tmp/archiso/EFI/{archiso,boot}
+
It is [https://www.linux-kvm.org/downloads/lersek/ovmf-whitepaper-c770f8c.txt advised] to make a local copy of the non-volatile variable store for your virtual machine:
# cp /tmp/archiso/arch/boot/x86_64/vmlinuz /tmp/archiso/EFI/archiso/vmlinuz.efi
 
# cp /tmp/archiso/arch/boot/x86_64/archiso.img /tmp/archiso/EFI/archiso/archiso.img
 
# cp /tmp/archiso_efiboot/EFI/boot/bootx64.efi /tmp/archiso/EFI/boot/bootx64.efi
 
# cp /tmp/archiso_efiboot/EFI/boot/startup.nsh /tmp/archiso/EFI/boot/startup.nsh
 
  
4. Find out the filesystem label to be used for the USB by reading "{{ic|1=archisolabel=}}" part in {{ic|/tmp/archiso/EFI/boot/startup.nsh}}. For example if {{ic|/tmp/archiso/EFI/boot/startup.nsh}} has {{ic|1=archisolabel=ARCH_201208}} then the filesystem label to be used is {{ic|ARCH_201208}} .  
+
$ cp /usr/share/ovmf/x64/OVMF_VARS.fd my_uefi_vars.bin
  
5. Create a directory {{ic|/tmp/archisousb}} . Format the USB drive as FAT32 (or FAT16) (no other filesystem is supported) and set the filesystem label same as the one obtained in step 4, and mount it to {{ic|/tmp/archisousb}} .
+
To use the OVMF firmware and this variable store, add following to your QEMU command:
  
6. Copy the contents of {{ic|/tmp/archiso}} to {{ic|/tmp/archisousb}} and then umount {{ic|/tmp/archisousb}} .
+
-drive if=pflash,format=raw,readonly,file=/usr/share/ovmf/x64/OVMF_CODE.fd \
 +
-drive if=pflash,format=raw,file=my_uefi_vars.bin
  
=== [[Archboot]] ===
+
For example:
  
1. Create a directory {{ic|/tmp/archboot}} and extract the archiso file contents to it.
+
$ qemu-system-x86_64 -enable-kvm -m 1G -drive if=pflash,format=raw,readonly,file=/usr/share/ovmf/x64/OVMF_CODE.fd -drive if=pflash,format=raw,file=my_uefi_vars.bin …
  
{{Note|Follow steps 2 and 3 only if {{ic|/tmp/archboot/EFI/boot/bootx64.efi}} does not exist, even after extracting archboot iso to {{ic|/tmp/archboot}} .}}
+
=== DUET for BIOS only systems ===
  
2. Create a directory {{ic|/tmp/archboot_efiboot}} and extract {{ic|/tmp/archboot/boot/grub/grub_uefi_x86_64.bin}} to it using {{ic|7z}} command from {{Pkg|p7zip}} package.
+
DUET was a TianoCore project that enabled chainloading a full UEFI environment from a BIOS system, in a way similar to BIOS OS booting. This method is being discussed extensively in https://www.insanelymac.com/forum/topic/186440-linux-and-windows-uefi-boot-using-tianocore-duet-firmware/. Pre-build DUET images can be downloaded from one of the repos at https://gitlab.com/tianocore_uefi_duet_builds/tianocore_uefi_duet_installer. Specific instructions for setting up DUET is available at https://gitlab.com/tianocore_uefi_duet_builds/tianocore_uefi_duet_installer/blob/master/Migle_BootDuet_INSTALL.txt . However, as of November 2018, the DUET code has been removed from TianoCore git repository.
  
3. Run the below commands:
+
You can also try https://sourceforge.net/projects/cloverefiboot/ which provides modified DUET images that may contain some system specific fixes and is more frequently updated compared to the gitlab repos.
  
# mkdir -p /tmp/archboot/EFI/boot
+
== Troubleshooting ==
# cp /tmp/archboot_efiboot/EFI/boot/bootx64.efi /tmp/archboot/EFI/boot/bootx64.efi
 
  
4. Create a directory {{ic|/tmp/archbootusb}} . Format the USB drive as FAT32 (or FAT16) (no other filesystem is supported) and mount it to {{ic|/tmp/archbootusb}} .
+
=== Windows 7 will not boot in UEFI mode ===
  
5. Copy the contents of {{ic|/tmp/archboot}} to {{ic|/tmp/archbootusb}} and then umount {{ic|/tmp/archbootusb}} .
+
If you have installed Windows to a different hard disk with GPT partitioning and still have a MBR partitioned hard disk in your computer, then it is possible that the firmware (UEFI) is starting its CSM support (for booting MBR partitions) and therefore Windows will not boot. To solve this merge your MBR hard disk to GPT partitioning or disable the SATA port where the MBR hard disk is plugged in or unplug the SATA connector from this hard disk.
  
== Remove UEFI boot support from ISO ==
+
Mainboards with this kind of problem:
  
Most of the 32-bit EFI Macs and some 64-bit EFI Macs refuse to boot from a UEFI(X64)+BIOS bootable CD/DVD. In these cases the iso should be rebuilt without UEFI boot support, retaining only BIOS boot.
+
* Gigabyte Z77X-UD3H rev. 1.1 (UEFI version F19e)
 +
** The firmware option for booting "UEFI Only" does not prevent the firmware from starting CSM.
  
=== Archiso ===
+
=== Windows changes boot order ===
  
1. Obtain the ISO label from the output of {{ic|file <path_to_iso>}}. Let it be {{ic|ARCH_201208}} for example.
+
If you [[dual boot with Windows]] and your motherboard just boots Windows immediately instead of your chosen EFI application, there are several possible causes and workarounds.
  
2. Create a directory {{ic|/tmp/archiso}} and extract the archiso file contents to it.
+
* Ensure [[Dual boot with Windows#Fast_Start-Up|Fast Startup]] is disabled in your Windows power options
 +
* Ensure [[Secure Boot]] is disabled in your BIOS (if you are not using a signed boot loader)
 +
* Ensure your UEFI boot order does not have Windows Boot Manager set first e.g. using [[#efibootmgr]] and what you see in the configuration tool of the UEFI. Some motherboards override by default any settings set with efibootmgr by Windows if it detects it. This is confirmed in a Packard Bell laptop.
 +
* If your motherboard is booting the default boot path ({{ic|\EFI\BOOT\BOOTX64.EFI}}), this file may have been overwritten with the Windows boot loader. Try setting the correct boot path e.g. using [[#efibootmgr]].
 +
* If the previous steps do not work, you can tell the Windows boot loader to run a different EFI application. From a Windows Administrator command prompt: {{bc|# bcdedit /set "{bootmgr}" path "\EFI\''path''\''to''\''app.efi''"}}
 +
* Alternatively, you can set a startup script in Windows that ensures that the boot order is set correctly every time you boot Windows.
 +
*# Open a command prompt with admin privlages. Run {{ic|bcdedit /enum firmware}} and find your desired boot entry.
 +
*# Copy the Identifier, including the brackets, e.g. {{ic|<nowiki>{31d0d5f4-22ad-11e5-b30b-806e6f6e6963}</nowiki>}}
 +
*# Create a batch file with the command {{ic|bcdedit /set "{fwbootmgr}" DEFAULT "{''copied boot identifier''}"}}
 +
*# Open ''gpedit.msc'' and under ''Local Computer Policy > Computer Configuration > Windows Settings > Scripts(Startup/Shutdown)'', choose ''Startup''
 +
*# Under the ''Scripts'' tab, choose the ''Add'' button, and select your batch file
  
3. Run xorriso (part of {{Pkg|libisoburn}} package) as shown below:
+
=== USB media gets struck with black screen ===
  
$ xorriso -as mkisofs -iso-level 3 \
+
This issue can occur due to [[KMS]] issue. Try [[Kernel mode setting#Disabling_modesetting|Disabling KMS]] while booting the USB.
          -full-iso9660-filenames \
 
          -volid "ARCH_201208" \
 
          -appid "Arch Linux Live/Rescue CD" \
 
          -publisher "Arch Linux <http://www.archlinux.org>" \
 
          -preparer "prepared by user" \
 
          -eltorito-boot isolinux/isolinux.bin \
 
          -eltorito-catalog isolinux/boot.cat \
 
          -no-emul-boot -boot-load-size 4 -boot-info-table \
 
          -isohybrid-mbr "/tmp/archiso/isolinux/isohdpfx.bin" \
 
          -output "/tmp/archiso.iso" "/tmp/archiso/"
 
  
4. Burn {{ic|/tmp/archiso.iso}} to a CD and boot into your Mac using that CD.
+
=== UEFI boot loader does not show up in firmware menu ===
  
=== [[Archboot]] ===
+
On certain UEFI motherboards like some boards with an Intel Z77 chipset, adding entries with {{ic|efibootmgr}} or {{ic|bcfg}} from the UEFI Shell will not work because they do not show up on the boot menu list after being added to NVRAM.
  
1. Create a directory {{ic|/tmp/archboot}} and extract the archboot iso file contents to it.
+
This issue is caused because the motherboards can only load Microsoft Windows. To solve this you have to place the ''.efi'' file in the location that Windows uses.
  
2. Run xorriso (part of {{Pkg|libisoburn}} package) as shown below:
+
Copy the {{ic|bootx64.efi}} file from the Arch Linux installation medium ({{ic|FSO:}}) to the Microsoft directory your [[ESP]] partition on your hard drive ({{ic|FS1:}}). Do this by booting into EFI shell and typing:
  
  $ xorriso -as mkisofs -iso-level 3 -rock -joliet \
+
  Shell> mkdir FS1:\EFI\Microsoft
          -max-iso9660-filenames -omit-period \
+
Shell> mkdir FS1:\EFI\Microsoft\Boot
          -omit-version-number -allow-leading-dots \
+
Shell> cp FS0:\EFI\BOOT\bootx64.efi FS1:\EFI\Microsoft\Boot\bootmgfw.efi
          -relaxed-filenames -allow-lowercase -allow-multidot \
 
          -volid "ARCHBOOT" -preparer "prepared by user" \
 
          -eltorito-boot boot/syslinux/isolinux.bin \
 
          -eltorito-catalog boot/syslinux/boot.cat \
 
          -no-emul-boot -boot-load-size 4 -boot-info-table \
 
          -isohybrid-mbr /tmp/archboot/boot/syslinux/isohdpfx.bin \
 
          -output "/tmp/archboot.iso" "/tmp/archboot/"
 
  
3. Burn {{ic|/tmp/archboot.iso}} to a CD and boot into your Mac using that CD.
+
After reboot, any entries added to NVRAM should show up in the boot menu.
  
 
== See also ==
 
== See also ==
  
* Wikipedia's page on [http://en.wikipedia.org/wiki/UEFI UEFI]
+
* [[Wikipedia:UEFI]]
* Wikipedia's page on [http://en.wikipedia.org/wiki/EFI_System_partition UEFI SYSTEM Partition]
+
* [https://www.uefi.org/home/ UEFI Forum] - contains the official [https://uefi.org/specifications UEFI Specifications] - GUID Partition Table is part of UEFI Specification
* [http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob_plain;f=Documentation/x86/x86_64/uefi.txt;hb=HEAD Linux Kernel UEFI Documentation]
+
* [https://www.happyassassin.net/2014/01/25/uefi-boot-how-does-that-actually-work-then/ UEFI boot: how does that actually work, then? - A blog post by AdamW]
* [http://www.uefi.org/home/ UEFI Forum] - contains the official [http://www.uefi.org/specs/ UEFI Specifications] - GUID Partition Table is part of UEFI Specification
+
* [https://www.kernel.org/doc/Documentation/x86/x86_64/uefi.txt Linux Kernel x86_64 UEFI Documentation]
* [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=Welcome_to_TianoCore Intel's Tianocore Project] for Open-Source UEFI firmware which includes DuetPkg for direct BIOS based booting and OvmfPkg used in QEMU and Oracle VirtualBox
+
* [https://www.intel.com/content/www/us/en/architecture-and-technology/unified-extensible-firmware-interface/efi-homepage-general-technology.html Intel's page on EFI]
* [http://www.intel.com/technology/efi/ Intel's page on EFI]
+
* [https://firmware.intel.com/ Intel Architecture Firmware Resource Center]
* [http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/efi-boot-process.html FGA: The EFI boot process]
+
* [https://firmware.intel.com/blog/linux-efi-boot-stub Matt Fleming - The Linux EFI Boot Stub]
* [http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx Microsoft's Windows and GPT FAQ] - Contains info on Windows UEFI booting also
+
* [https://firmware.intel.com/blog/accessing-uefi-variables-linux Matt Fleming - Accessing UEFI Variables from Linux]
* [https://gitorious.org/tianocore_uefi_duet_builds/pages/Windows_x64_BIOS_to_UEFI Convert Windows Vista SP1+ or 7 x86_64 boot from BIOS-MBR mode to UEFI-GPT mode without Reinstall]
+
* [https://www.rodsbooks.com/linux-uefi/ Rod Smith - Linux on UEFI: A Quick Installation Guide]
* [https://gitorious.org/tianocore_uefi_duet_builds/pages/Linux_Windows_BIOS_UEFI_boot_USB Create a Linux BIOS+UEFI and Windows x64 BIOS+UEFI bootable USB drive]
 
* [http://rodsbooks.com/bios2uefi/ Rod Smith - A BIOS to UEFI Transformation]
 
 
* [https://lkml.org/lkml/2011/6/8/322 UEFI Boot problems on some newer machines (LKML)]
 
* [https://lkml.org/lkml/2011/6/8/322 UEFI Boot problems on some newer machines (LKML)]
* [http://software.intel.com/en-us/articles/efi-shells-and-scripting/ EFI Shells and Scripting - Intel Documentation]
+
* [https://linuxplumbers.ubicast.tv/videos/plumbing-uefi-into-linux/ LPC 2012 Plumbing UEFI into Linux]
* [http://software.intel.com/en-us/articles/uefi-shell/ UEFI Shell  - Intel Documentation]
+
* [https://linuxplumbers.ubicast.tv/videos/uefi-tutorial-part-1/ LPC 2012 UEFI Tutorial : part 1]
* [http://www.hpuxtips.es/?q=node/293 UEFI Shell - bcfg command info]
+
* [https://linuxplumbers.ubicast.tv/videos/uefi-tutorial-part-2/ LPC 2012 UEFI Tutorial : part 2]
* [http://hackthejoggler.freeforums.org/download/file.php?id=28 Some useful 32-bit UEFI Shell utilities]
+
* [https://www.tianocore.org/ Intel's TianoCore Project] for Open-Source UEFI firmware which includes DuetPkg for direct BIOS based booting and OvmfPkg used in QEMU and Oracle VirtualBox
 +
* [https://jdebp.eu/FGA/efi-boot-process.html FGA: The EFI boot process]
 +
* [https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/windows-and-gpt-faq Microsoft's Windows and GPT FAQ]
 +
* [https://gitlab.com/tianocore_uefi_duet_builds/tianocore_uefi_duet_installer/wikis/Windows_x64_BIOS_to_UEFI Convert Windows x64 from BIOS-MBR mode to UEFI-GPT mode without Reinstall]
 +
* [https://gitlab.com/tianocore_uefi_duet_builds/tianocore_uefi_duet_installer/wikis/Linux_Windows_BIOS_UEFI_boot_USB Create a Linux BIOS+UEFI and Windows x64 BIOS+UEFI bootable USB drive]
 +
* [https://rodsbooks.com/bios2uefi/ Rod Smith - A BIOS to UEFI Transformation]
 +
* [https://software.intel.com/en-us/articles/efi-shells-and-scripting/ EFI Shells and Scripting - Intel Documentation]
 +
* [https://software.intel.com/en-us/articles/uefi-shell/ UEFI Shell  - Intel Documentation]
 +
* [https://web.archive.org/web/20130929114218/http://www.hpuxtips.es/?q=node/293 UEFI Shell - bcfg command info]

Latest revision as of 01:35, 10 June 2019

Warning: While the choice to install in UEFI mode is forward looking, early vendor UEFI implementations may carry more bugs than their BIOS counterparts. It is advised to do a search relating to your particular motherboard model before proceeding.

The Unified Extensible Firmware Interface (UEFI or EFI for short) is a new model for the interface between operating systems and firmware. It provides a standard environment for booting an operating system and running pre-boot applications.

It is distinct from the commonly used "MBR boot code" method followed for BIOS systems. See Arch boot process for their differences and the boot process using UEFI. To set up UEFI boot loaders, see Arch boot process#Boot loader.

UEFI versions

  • UEFI started as Intel's EFI in versions 1.x.
  • Later, a group of companies called the UEFI Forum took over its development, which renamed it as Unified EFI starting with version 2.0.
  • Unless specified as EFI 1.x, EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware.
  • Apple's EFI implementation is neither a EFI 1.x version nor UEFI 2.x version but mixes up both. This kind of firmware does not fall under any one (U)EFI specification and therefore is not a standard UEFI firmware. Unless stated explicitly, these instructions are general and some of them may not work or may be different in Apple Macs.

The latest UEFI specification can be found at https://uefi.org/specifications.

UEFI firmware bitness

Under UEFI, every program whether it is an OS loader or a utility (e.g. a memory testing app or recovery tool), should be a EFI application corresponding to the UEFI firmware bitness/architecture.

The vast majority of UEFI firmwares, including recent Apple Macs, use x86_64 UEFI firmware. The only known devices that use IA32 (32-bit) UEFI are older (pre 2008) Apple Macs, Intel Atom System-on-Chip systems (as on 2 November 2013)[1] and some older Intel server boards that are known to operate on Intel EFI 1.10 firmware.

An x86_64 UEFI firmware does not include support for launching 32-bit EFI applications (unlike x86_64 Linux and Windows versions which include such support). Therefore the EFI application must be compiled for that specific firmware processor bitness/architecture.

Note: The official ISO does not support booting on 32-bit (IA32) UEFI systems, see #Booting 64-bit kernel on 32-bit UEFI for available workarounds. The installed system will require using a boot loader that supports IA32 UEFI, for example, GRUB with the i386-efi target.

Checking the firmware bitness

The firmware bitness can be checked from a booted operating system.

From Linux

On distributions running Linux kernel 4.0 or newer, the UEFI firmware bitness can be found via the sysfs interface. Run:

$ cat /sys/firmware/efi/fw_platform_size

It will return 64 for a 64-bit (x86_64) UEFI or 32 for a 32-bit (IA32) UEFI. If the file does not exist, then you have not booted in UEFI mode.

From macOS

Pre-2008 Macs mostly have IA32 EFI firmware while >=2008 Macs have mostly x86_64 EFI. All Macs capable of running Mac OS X Snow Leopard 64-bit Kernel have x86_64 EFI 1.x firmware.

To find out the arch of the EFI firmware in a Mac, type the following into the Mac OS X terminal:

$ ioreg -l -p IODeviceTree | grep firmware-abi

If the command returns EFI32 then it is IA32 (32-bit) EFI firmware. If it returns EFI64 then it is x86_64 EFI firmware. Most of the Macs do not have UEFI 2.x firmware as Apple's EFI implementation is not fully compliant with UEFI 2.x specification.

From Microsoft Windows

64-bit versions of Windows do not support booting on a 32-bit UEFI. So, if you have a 32-bit version of Windows booted in UEFI mode, you have a 32-bit UEFI.

To check the bitness run msinfo32.exe. In the System Summary section look at the values of "System Type" and "BIOS mode".

For a 64-bit Windows on a 64-bit UEFI it will be System Type: x64-based PC and BIOS mode: UEFI, for a 32-bit Windows on a 32-bit UEFI - System Type: x86-based PC and BIOS mode: UEFI. If the "BIOS mode" is not UEFI, then Windows is not installed in UEFI mode.

Linux kernel config options for UEFI

The required Linux Kernel configuration options[2] for UEFI systems are:

CONFIG_RELOCATABLE=y
CONFIG_EFI=y
CONFIG_EFI_STUB=y
CONFIG_X86_SYSFB=y
CONFIG_FB_SIMPLE=y
CONFIG_FRAMEBUFFER_CONSOLE=y

UEFI Runtime Variables Support (efivarfs filesystem - /sys/firmware/efi/efivars). This option is important as this is required to manipulate UEFI runtime variables using tools like /usr/bin/efibootmgr. The below config option has been added in kernel 3.10 and above.

CONFIG_EFIVAR_FS=y

UEFI Runtime Variables Support (old efivars sysfs interface - /sys/firmware/efi/vars). This option should be disabled to prevent any potential issues with both efivarfs and sysfs-efivars enabled.

CONFIG_EFI_VARS=n

GUID Partition Table (GPT) config option - mandatory for UEFI support

CONFIG_EFI_PARTITION=y

EFI mixed-mode support - to boot a x64_64 kernel on a IA32 UEFI.

CONFIG_EFI_MIXED=y
Note: All of the above options are enabled in Arch Linux kernels in the official repositories.

UEFI variables

UEFI defines variables through which an operating system can interact with the firmware. UEFI boot variables are used by the boot loader and used by the OS only for early system start-up. UEFI runtime variables allow an OS to manage certain settings of the firmware like the UEFI boot manager or managing the keys for UEFI Secure Boot protocol etc. You can get the list using:

$ efivar --list

UEFI variables support in Linux kernel

Linux kernel exposes UEFI variables data to userspace via efivarfs (EFI VARiable FileSystem) interface (CONFIG_EFIVAR_FS) - mounted using efivarfs kernel module at /sys/firmware/efi/efivars - it has no maximum per-variable size limitation and supports UEFI Secure Boot variables. Introduced in kernel 3.8.

Requirements for UEFI variable support

  1. Kernel should be booted in UEFI mode via EFISTUB (optionally using a boot manager) or by a UEFI boot loader (using either the EFI handover protocol or the UEFI LoadImage function), not via BIOS or CSM, or Apple's Boot Camp which is also a CSM.
  2. EFI Runtime Services support should be present in the kernel (CONFIG_EFI=y, check if present with zgrep CONFIG_EFI /proc/config.gz).
  3. EFI Runtime Services in the kernel SHOULD NOT be disabled via kernel cmdline, i.e. noefi kernel parameter SHOULD NOT be used.
  4. efivarfs filesystem should be mounted at /sys/firmware/efi/efivars, otherwise follow #Mount efivarfs section below.
  5. efivar should list (option -l/--list) the UEFI variables without any error.

If UEFI Variables support does not work even after the above conditions are satisfied, try the below workarounds:

  1. If any userspace tool is unable to modify UEFI variable data, check for existence of /sys/firmware/efi/efivars/dump-* files. If they exist, delete them, reboot and retry again.
  2. If the above step does not fix the issue, try booting with efi_no_storage_paranoia kernel parameter to disable kernel UEFI variable storage space check that may prevent writing/modification of UEFI variables.
Warning: efi_no_storage_paranoia should only be used when needed and should not be left as a normal boot option. The effect of this kernel command line parameter turns off a safeguard that was put in place to help avoid the bricking of machines when the NVRAM gets too full. See FS#34641 for more information.

Mount efivarfs

If efivarfs is not automatically mounted at /sys/firmware/efi/efivars by systemd during boot, then you need to manually mount it to expose UEFI variables to userspace tools like efibootmgr:

# mount -t efivarfs efivarfs /sys/firmware/efi/efivars
Note: The above command should be run both outside (before) and inside the chroot, if any.

See efivarfs.txt for kernel documentation.

Userspace tools

There are few tools that can access/modify the UEFI variables, namely

  • efivar — Library and Tool to manipulate UEFI variables (used by efibootmgr)
https://github.com/rhboot/efivar || efivar, efivar-gitAUR
  • efibootmgr — Tool to manipulate UEFI Firmware Boot Manager Settings
https://github.com/rhboot/efibootmgr || efibootmgr
  • uefivars — Dumps list of UEFI variables with some additional PCI related info (uses efibootmgr code internally)
https://github.com/fpmurphy/Various/tree/master/uefivars-2.0 || uefivars-gitAUR
  • efitools — Tools for manipulating UEFI secure boot platforms
https://git.kernel.org/pub/scm/linux/kernel/git/jejb/efitools.git || efitools
  • Ubuntu's Firmware Test Suite — Test suite that performs sanity checks on Intel/AMD PC firmware
https://wiki.ubuntu.com/FirmwareTestSuite/ || fwts-gitAUR

efibootmgr

You will have to install the efibootmgr package.

Note:
  • If efibootmgr does not work on your system, you can reboot into #UEFI Shell and use bcfg to create a boot entry for the bootloader.
  • If you are unable to use efibootmgr, some UEFI firmwares allow users to directly manage UEFI boot entries from within its boot-time interface. For example, some firmwares have an "Add New Boot Option" choice which enables you to select a local EFI system partition and manually enter the EFI application location e.g. \EFI\refind\refind_x64.efi.
  • The below commands use rEFInd boot manager as example.

To add a new boot option using efibootmgr you need to know three things:

  1. The disk containing the EFI system partition (ESP). E.g.: /dev/sda, /dev/nvme0n1.
  2. The partition number of the ESP on that disk. The Y in /dev/sdaY or /dev/nvme0n1pY.
  3. The path to the EFI application (relative to the root of the ESP)

For example, if you want to add a boot option for /efi/EFI/refind/refind_x64.efi where /efi is the mount point of the ESP, run

$ findmnt /efi
TARGET SOURCE    FSTYPE OPTIONS
/efi   /dev/sda1 vfat   rw,flush,tz=UTC

In this example, this indicates that the ESP is on disk /dev/sda and has partition number 1. The path to the EFI application relative to the root of the ESP is /EFI/refind/refind_x64.efi. So you would create the boot entry as follows:

# efibootmgr --create --disk /dev/sda --part 1 --loader /EFI/refind/refind_x64.efi --label "rEFInd Boot Manager" --verbose

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: /dev/nvme0n1p1 is a partition not a disk, the partition number should be specified using the --part option. (Discuss in Talk:Unified Extensible Firmware Interface#)
# efibootmgr --create --disk /dev/nvme0n1p1 --loader /EFI/refind/refind_x64.efi --label "rEFINd Boot Manager" --verbose

See efibootmgr(8) or efibootmgr README for more info.

Note: UEFI uses backward slash \ as path separator but efibootmgr automatically converts UNIX-style / path separators.

UEFI Shell

The UEFI Shell is a shell/terminal for the firmware which allows launching EFI applications which include UEFI bootloaders. Apart from that, the shell can also be used to obtain various other information about the system or the firmware like memory map (memmap), modifying boot manager variables (bcfg), running partitioning programs (diskpart), loading UEFI drivers, editing text files (edit), hexedit etc.

Obtaining UEFI Shell

You can download a BSD licensed UEFI Shell from Intel's TianoCore UDK/EDK2 project:

Shell v2 works best in UEFI 2.3+ systems and is recommended over Shell v1 in those systems. Shell v1 should work in all UEFI systems irrespective of the spec. version the firmware follows. More info at ShellPkg and this mail.

Launching UEFI Shell

Few Asus and other AMI Aptio x86_64 UEFI firmware based motherboards (from Sandy Bridge onwards) provide an option called "Launch EFI Shell from filesystem device" . For those motherboards, download the x86_64 UEFI Shell and copy it to your EFI system partition as <EFI_SYSTEM_PARTITION>/shellx64.efi.

Systems with Phoenix SecureCore Tiano UEFI firmware are known to have embedded UEFI Shell which can be launched using either F6, F11 or F12 key.

Note: If you are unable to launch UEFI Shell from the firmware directly using any of the above mentioned methods, create a FAT32 USB pen drive with Shell.efi copied as (USB)/EFI/BOOT/BOOTx64.EFI. This USB should come up in the firmware boot menu. Launching this option will launch the UEFI Shell for you.

Important UEFI Shell commands

UEFI Shell commands usually support -b option which makes output pause after each page. Run help -b to list available internal commands. Available commands are either built into the shell or discrete EFI applications.

For more info see Intel Scripting Guide 2008 and Intel "Course" 2011.

bcfg

bcfg modifies the UEFI NVRAM entries which allows the user to change the boot entries or driver options. This command is described in detail in page 83 (Section 5.3) of the UEFI Shell Specification 2.0 document.

Note:
  • Try bcfg only if efibootmgr fails to create working boot entries on your system.
  • UEFI Shell v1 official binary does not support bcfg command. See #Obtaining UEFI Shell for a modified UEFI Shell v2 binary which may work in UEFI pre-2.3 firmwares.

To dump a list of current boot entries:

Shell> bcfg boot dump -v

To add a boot menu entry for rEFInd (for example) as 4th (numbering starts from zero) option in the boot menu:

Shell> bcfg boot add 3 FS0:\EFI\refind\refind_x64.efi "rEFInd"

where FS0: is the mapping corresponding to the EFI system partition and FS0:\EFI\refind\refind_x64.efi is the file to be launched.

To add an entry to boot directly into your system without a bootloader, configure a boot option using your kernel as an EFISTUB:

Shell> bcfg boot add N fsV:\vmlinuz-linux "Arch Linux"
Shell> bcfg boot -opt N "root=/dev/sdX# initrd=\initramfs-linux.img"

where N is the priority, V is the volume number of your EFI system partition, and /dev/sdX# is your root partition.

To remove the 4th boot option:

Shell> bcfg boot rm 3

To move the boot option #3 to #0 (i.e. 1st or the default entry in the UEFI Boot menu):

Shell> bcfg boot mv 3 0

For bcfg help text:

Shell> help bcfg -v -b

or:

Shell> bcfg -? -v -b

map

map displays a list of device mappings i.e. the names of available file systems (FS0) and storage devices (blk0).

Before running file system commands such as cd or ls, you need to change the shell to the appropriate file system by typing its name:

Shell> FS0:
FS0:\> cd EFI/

edit

edit provides a basic text editor with an interface similar to nano, but slightly less functional. It handles UTF-8 encoding and takes care or LF vs CRLF line endings.

For example, to edit rEFInd's refind.conf in the EFI system partition (FS0: in the firmware),

Shell> edit FS0:\EFI\refind\refind.conf

Type Ctrl-E for help.

UEFI drivers

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: Explain what are and how to use UEFI drivers. (Discuss in Talk:Unified Extensible Firmware Interface#)

UEFI bootable media

Create UEFI bootable USB from ISO

Follow USB flash installation media#BIOS and UEFI bootable USB.

Remove UEFI boot support from optical media

Note: This section mentions removing UEFI boot support from a CD/DVD only (Optical Media), not from a USB flash drive.

Most of the 32-bit EFI Macs and some 64-bit EFI Macs refuse to boot from a UEFI(X64)+BIOS bootable CD/DVD. If one wishes to proceed with the installation using optical media, it might be necessary to remove UEFI support first.

  • Mount the official installation media and obtain the archisolabel as shown in the previous section.
# mount -o loop input.iso /mnt/iso
  • Then rebuild the ISO, excluding the UEFI optical media booting support, using xorriso from libisoburn. Be sure to set the correct archisolabel, e.g. "ARCH_201411" or similar:
$ xorriso -as mkisofs -iso-level 3 \
    -full-iso9660-filenames\
    -volid "archisolabel" \
    -appid "Arch Linux CD" \
    -publisher "Arch Linux <https://www.archlinux.org>" \
    -preparer "prepared by $USER" \
    -eltorito-boot isolinux/isolinux.bin \
    -eltorito-catalog isolinux/boot.cat \
    -no-emul-boot -boot-load-size 4 -boot-info-table \
    -isohybrid-mbr "/mnt/iso/isolinux/isohdpfx.bin" \
    -output output.iso /mnt/iso/
  • Burn output.iso to optical media and proceed with installation normally.

Booting 64-bit kernel on 32-bit UEFI

Official ISO (Archiso) does not support booting on 32-bit (IA32) UEFI systems (FS#53182) since it uses EFISTUB (via systemd-boot boot manager for menu) for booting the kernel in UEFI mode. To boot a 64-bit kernel with 32-bit UEFI you have to use a boot loader that does not rely on EFI boot stub for launching kernels.

Tip: Archboot iso supports booting on 32-bit (IA32) UEFI systems.

Using GRUB

This section describes how to setup GRUB as the USB's UEFI bootloader.

# echo 'configfile ${cmdpath}/grub.cfg' > /tmp/grub.cfg
# grub-mkstandalone -d /usr/lib/grub/i386-efi -O i386-efi --modules="part_gpt part_msdos" --locales="en@quot" --themes="" -o "/mnt/usb/EFI/boot/bootia32.efi" "boot/grub/grub.cfg=/tmp/grub.cfg" -v
  • Create /mnt/usb/EFI/boot/grub.cfg with the following contents (replace ARCH_YYYYMM with the required archiso label e.g. ARCH_201507):
Tip:
  • The archiso label can be aquired from the .iso file with isoinfo from cdrtools or iso-info from libcdio.
  • The given configuration entries can also be entered inside a GRUB command-shell.

For the official ISO:

/mnt/usb/EFI/boot/grub.cfg
insmod part_gpt
insmod part_msdos
insmod fat

insmod efi_gop
insmod efi_uga
insmod video_bochs
insmod video_cirrus

insmod font

if loadfont "${prefix}/fonts/unicode.pf2" ; then
    insmod gfxterm
    set gfxmode="1024x768x32;auto"
    terminal_input console
    terminal_output gfxterm
fi

menuentry "Arch Linux archiso x86_64 UEFI USB" {
    set gfxpayload=keep
    search --no-floppy --set=root --label ARCH_YYYYMM
    linux /arch/boot/x86_64/vmlinuz archisobasedir=arch archisolabel=ARCH_YYYYMM add_efi_memmap
    initrd /arch/boot/intel_ucode.img /arch/boot/x86_64/archiso.img
}

Durring installation, in the boot loader installation step, install GRUB using the option --target=i386-efi.

Testing UEFI in systems without native support

OVMF for virtual machines

OVMF is a TianoCore project to enable UEFI support for Virtual Machines. OVMF contains a sample UEFI firmware and a separate non-volatile variable store for QEMU.

You can install ovmf from the extra repository.

It is advised to make a local copy of the non-volatile variable store for your virtual machine:

$ cp /usr/share/ovmf/x64/OVMF_VARS.fd my_uefi_vars.bin

To use the OVMF firmware and this variable store, add following to your QEMU command:

-drive if=pflash,format=raw,readonly,file=/usr/share/ovmf/x64/OVMF_CODE.fd \
-drive if=pflash,format=raw,file=my_uefi_vars.bin

For example:

$ qemu-system-x86_64 -enable-kvm -m 1G -drive if=pflash,format=raw,readonly,file=/usr/share/ovmf/x64/OVMF_CODE.fd -drive if=pflash,format=raw,file=my_uefi_vars.bin …

DUET for BIOS only systems

DUET was a TianoCore project that enabled chainloading a full UEFI environment from a BIOS system, in a way similar to BIOS OS booting. This method is being discussed extensively in https://www.insanelymac.com/forum/topic/186440-linux-and-windows-uefi-boot-using-tianocore-duet-firmware/. Pre-build DUET images can be downloaded from one of the repos at https://gitlab.com/tianocore_uefi_duet_builds/tianocore_uefi_duet_installer. Specific instructions for setting up DUET is available at https://gitlab.com/tianocore_uefi_duet_builds/tianocore_uefi_duet_installer/blob/master/Migle_BootDuet_INSTALL.txt . However, as of November 2018, the DUET code has been removed from TianoCore git repository.

You can also try https://sourceforge.net/projects/cloverefiboot/ which provides modified DUET images that may contain some system specific fixes and is more frequently updated compared to the gitlab repos.

Troubleshooting

Windows 7 will not boot in UEFI mode

If you have installed Windows to a different hard disk with GPT partitioning and still have a MBR partitioned hard disk in your computer, then it is possible that the firmware (UEFI) is starting its CSM support (for booting MBR partitions) and therefore Windows will not boot. To solve this merge your MBR hard disk to GPT partitioning or disable the SATA port where the MBR hard disk is plugged in or unplug the SATA connector from this hard disk.

Mainboards with this kind of problem:

  • Gigabyte Z77X-UD3H rev. 1.1 (UEFI version F19e)
    • The firmware option for booting "UEFI Only" does not prevent the firmware from starting CSM.

Windows changes boot order

If you dual boot with Windows and your motherboard just boots Windows immediately instead of your chosen EFI application, there are several possible causes and workarounds.

  • Ensure Fast Startup is disabled in your Windows power options
  • Ensure Secure Boot is disabled in your BIOS (if you are not using a signed boot loader)
  • Ensure your UEFI boot order does not have Windows Boot Manager set first e.g. using #efibootmgr and what you see in the configuration tool of the UEFI. Some motherboards override by default any settings set with efibootmgr by Windows if it detects it. This is confirmed in a Packard Bell laptop.
  • If your motherboard is booting the default boot path (\EFI\BOOT\BOOTX64.EFI), this file may have been overwritten with the Windows boot loader. Try setting the correct boot path e.g. using #efibootmgr.
  • If the previous steps do not work, you can tell the Windows boot loader to run a different EFI application. From a Windows Administrator command prompt:
    # bcdedit /set "{bootmgr}" path "\EFI\path\to\app.efi"
  • Alternatively, you can set a startup script in Windows that ensures that the boot order is set correctly every time you boot Windows.
    1. Open a command prompt with admin privlages. Run bcdedit /enum firmware and find your desired boot entry.
    2. Copy the Identifier, including the brackets, e.g. {31d0d5f4-22ad-11e5-b30b-806e6f6e6963}
    3. Create a batch file with the command bcdedit /set "{fwbootmgr}" DEFAULT "{copied boot identifier}"
    4. Open gpedit.msc and under Local Computer Policy > Computer Configuration > Windows Settings > Scripts(Startup/Shutdown), choose Startup
    5. Under the Scripts tab, choose the Add button, and select your batch file

USB media gets struck with black screen

This issue can occur due to KMS issue. Try Disabling KMS while booting the USB.

UEFI boot loader does not show up in firmware menu

On certain UEFI motherboards like some boards with an Intel Z77 chipset, adding entries with efibootmgr or bcfg from the UEFI Shell will not work because they do not show up on the boot menu list after being added to NVRAM.

This issue is caused because the motherboards can only load Microsoft Windows. To solve this you have to place the .efi file in the location that Windows uses.

Copy the bootx64.efi file from the Arch Linux installation medium (FSO:) to the Microsoft directory your ESP partition on your hard drive (FS1:). Do this by booting into EFI shell and typing:

Shell> mkdir FS1:\EFI\Microsoft
Shell> mkdir FS1:\EFI\Microsoft\Boot
Shell> cp FS0:\EFI\BOOT\bootx64.efi FS1:\EFI\Microsoft\Boot\bootmgfw.efi

After reboot, any entries added to NVRAM should show up in the boot menu.

See also