Still need bootable USB. When Clover Boot Manager appear go to option and make sure that it don’t inject Nvidia and don’t use Nvidia Web Driver, then select internalhfs ( Boot Mac OS X from. 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.

This article or section is out of date.

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.

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:

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:

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 booted in UEFI mode.

Linux kernel config options for UEFI

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

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.

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.

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

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

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:

UEFI variables support in Linux kernel

Linux kernel exposes UEFI variables data to userspace via efivarfs (EFIVARiable 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, 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 listing of the UEFI variables (efivar -l) leads to efivar: error listing variables: Function not implemented and the system is booted into a realtime kernel, add efi=runtime to the kernel parameters and reboot (efivarfs functionality is disabled by default on those kernels).
2. 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.
3. 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.

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:

See efivarfs.html 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-git^AUR

• 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-git^AUR

• 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-git^AUR

efibootmgr

You will have to install the efibootmgr package.

• 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. EFIrefindrefind_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

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:

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

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 obtain a BSD licensed UEFI Shell from the TianoCore EDK2 project:

• Shell v2:
  • On the Arch install medium: /shellx64.efi. A copy of /usr/share/edk2-shell/x64/Shell_Full.efi from the time the ISO was built.
  • edk2-shell provides x86_64 Shell for x86_64 (64-bit) UEFI and IA32 Shell for IA32 (32-bit) UEFI - compiled directly from latest TianoCore EDK2 release.
  • uefi-shell-git^AUR 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.
• Shell v1:
  • Precompiled UEFI Shell v1 binaries from TianoCore (not updated anymore upstream as of Jan 10, 2014).
• Patched shells:
  • Precompiled UEFI Shell v2 binary with bcfg modified to work with UEFI pre-2.3 firmware - from Clover EFI bootloader.
  • Precompiled UEFI Shell v2 binary for compatibility with a broad range of firmwares - from the OpenCore bootloader. In the release archive: EFI/OC/Tools/OpenShell.efi.

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 information at ShellPkg and the EDK2 mailing list thread—Inclusion of UEFI shell in Linux distro iso.

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, copy the x86_64 UEFI Shell to the root of your EFI system partition, named as shellx64.efi.

• The Arch Linux installation medium has shellx64.efi at the root of the volume.
• rEFInd and systemd-boot will automatically add a boot menu entry for the UEFI shell if shellx64.efi is in the root of the EFI system partition.

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.

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 96 (Section 5.3) of the UEFI Shell Specification 2.2 document.

• 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:

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

where FS0: is the mapping corresponding to the EFI system partition and FS0:EFIrefindrefind_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:

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:

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

For bcfg help text:

or:

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:

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),

Press Ctrl+e for help.

UEFI drivers

This article or section needs expansion.

UEFI bootable media

Create UEFI bootable USB from ISO

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

Remove UEFI boot support from optical media

• This section mentions removing UEFI boot support from a CD/DVD only (Optical Media booting via EL Torito), not from a USB flash drive.
• In order to hide the UEFI equipment on USB stick, use a partition editor after having copied the ISO to the flash drive. Remove the partition of type EF. Do not accept offers to convert to GPT.

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.

Extract the ISO skipping the UEFI-specific directories:

Then rebuild the ISO, excluding the UEFI optical media booting support, using xorriso(1) from libisoburn. Be sure to set the correct volume label, e.g. ARCH_202103; it can be acquired using file(1) on the original ISO.

Burn archlinux-version-x86_64-noUEFI.iso to optical media and proceed with installation normally.

Booting 64-bit kernel on 32-bit UEFI

This article or section needs expansion.

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.

Clover Bootable Usb Bootable

Using GRUB

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

• Create an editable USB Flash Installation.
• Create a GRUB standalone image for 32-bit UEFI systems by running the following commands:

• Create /mnt/EFI/boot/grub.cfg with the following contents (replace ARCH_YYYYMM with the ISO 9660 volume label e.g. ARCH_202010):

• The ISO's volume label can be acquired using file(1).
• The given configuration entries can also be entered inside a GRUB command-shell.

During 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 edk2-ovmf from the extra repository.

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

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

For example:

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.

To boot back into Arch Linux when you are stuck with Windows, reach Advanced startup in Windows by the Windows PowerShell command shutdown /r /o, or via Settings > Update & Security > Recovery > Advanced startup and select Restart now. When you have reached the Advanced startup menu, choose Use a device, which actually contains your UEFI boot options (not limited to USB or CD, but can also boot operating system in hard drive), and choose 'Arch Linux'.

• Ensure Fast Startup is disabled in your Windows power options
• Ensure Secure Boot is disabled in your firmware (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 (EFIBOOTBOOTX64.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 'EFIpathtoapp.efi'
• Alternatively, deactivate the Windows Boot Manager by running efibootmgr -A -b bootnumber as root. Replace bootnumber with the actual Windows Boot Manager boot number; you can see it by running efibootmgr with no options.
• 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 administrator privileges. 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:

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

System boots to EFI shell after hardware change or starting other operating system

This article or section needs language, wiki syntax or style improvements. See Help:Style for reference.

EFI stores state on the motherboard, called EFIVARS. Your bootloader (e.g. GRUB) may need to set up these variables in a certain way in order to boot. If your hardware configuration changes, your motherboard is replaced, or you boot into another operating system which overwrites these variables (Windows), you may be dumped into the EFI shell or boot menu (where your device is not listed). Upon attempting to boot Arch Linux since the EFIVARS are incorrect and EFI can no longer find your bootloader.

At this point, you can use the EFI shell to find and boot your bootloader manually. Usually something like:

Clover Boot Usb Stick

To prevent booting into the EFI shell again, you can install your bootloader to the default EFI boot location. To do this with GRUB's grub-install, see GRUB#Default/fallback boot path.

There is no guaranteed success for the 'Default/fallback boot path' method. Some board firmware (for example AsRock C2550D4I and C2750D4I) will search and boot the default locations on removable drives only. Booting from non removable drives (such as internal HDD, NVMe, etc.) requires fixing the efivars. For example using efibootmgr:

Boot entries created with efibootmgr fail to show up in UEFI

efibootmgr can fail to detect EDD 3.0 and as a result create unusable boot entries in NVRAM. See efibootmgr issue 86 for the details.

To work around this, when creating boot entries manually, add the -e 3 option to the efibootmgr command. E.g.

To fix boot loader installers, like grub-install and refind-install, create a wrapper script /usr/local/bin/efibootmgr and make it executable:

See also

• UEFI Forum - contains the official UEFI Specifications - GUID Partition Table is part of UEFI Specification
• 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