Boot efi from linux

EFISTUB

The Linux kernel supports EFISTUB booting which allows EFI firmware to load the kernel as an EFI executable. The option is enabled by default on Arch Linux kernels, or if compiling the kernel one can activate it by setting CONFIG_EFI_STUB=y in the Kernel configuration. See The EFI Boot Stub for more information.

With EFISTUB a kernel can be booted directly by a UEFI motherboard or indirectly using a boot loader. Using a boot loader is recommended if you have multiple kernel/initramfs pairs and your motherboard’s UEFI boot menu is not easy to use.

Contents

Preparing for EFISTUB

First, you must create an EFI system partition and choose how it is mounted. See EFI system partition#Mount the partition for all available ESP mounting options.

Booting EFISTUB

Using a boot manager

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

There are several UEFI boot managers which can provide additional options or simplify the process of UEFI booting — especially if you have multiple kernels/operating systems. See Arch boot process#Boot loader for more information.

Using UEFI directly

UEFI is designed to remove the need for an intermediate bootloader such as GRUB. If your motherboard has a good UEFI implementation, it is possible to embed the kernel parameters within a UEFI boot entry and for the motherboard to boot Arch directly. You can use efibootmgr or UEFI Shell v2 to modify your motherboard’s boot entries.

efibootmgr

To create a boot entry with efibootmgr that will load the kernel:

or create a boot entry with efibootmgr and hibernation on swap partition:

Where /dev/sdX and Y are the drive and partition number where the ESP is located. Change the root= and resume= parameters to reflect your Linux root and swap partitions, see kernel parameters for supported device name formats, and persistent block device naming for how to obtain the corresponding value. If omitted, then the first partition on /dev/sda is used as the ESP.

Note that the -u / —unicode argument in quotes is just the list of kernel parameters, so you may need to add additional parameters (e.g. for suspend to disk or microcode).

After adding the boot entry, you can verify the entry was added properly with:

To set the boot order:

Where XXXX is the number that appears in the output of efibootmgr command against each entry.

efibootmgr with .efi file

This article or section is a candidate for merging with systemd-boot#Preparing a unified kernel image.

If using cryptboot AUR and sbupdate-git AUR to generate your own keys for Secure Boot and sign the initramfs and kernel then create a bootable .efi image, efibootmgr can be used directly to boot the .efi file:

See efibootmgr(8) for an explanation of the options. To include microcode in a unified kernel image, concatenate it with the initramfs and use the resultant image with objtool.

Some UEFI implementations make it difficult to modify the NVRAM successfully using efibootmgr. If efibootmgr cannot successfully create an entry, you can use the bcfg command in UEFI Shell v2 (i.e., from the Arch Linux live iso).

First, find out the device number where your ESP resides with:

In this example, 1 is used as the device number. To list the contents of the ESP:

To view the current boot entries:

To add an entry for your kernel, use:

Where N is the location where the entry will be added in the boot menu. 0 is the first menu item. Menu items already existing will be shifted in the menu without being discarded.

Add the necessary kernel options by creating a file on your ESP:

In the file, add the boot line. For example:

Press F2 to save and then F3 to exit.

Add these options to your previous entry:

Repeat this process for any additional entries.

To remove a previously added item do:

kesboot

You can also simplify and automate the work with EFISTUB using a script from the kesboot-git AUR package. It also contains a pacman hook that can add and remove EFI variables during actions with packages.

First, install the package, and then configure the /etc/kesboot.conf file:

The package also contains a program for the initial configuration of the EFI boot. After mounting the ESP directory, run

More tools

This section is being considered for removal.

Some of the tools above, and more, are briefly discussed in rEFInd#Tools.

Using UEFI Shell

If you do not want to create a permanent boot entry it is possible to launch the kernel from UEFI Shell as if it is a normal UEFI application:

In this case, the kernel parameters are passed as normal parameters to the launched EFISTUB kernel file.

To avoid needing to remember all of your kernel parameters every time, you can save the executable command to a shell script such as archlinux.nsh on your UEFI System Partition, then run it with:

Using a startup.nsh script

Some UEFI implementations do not retain EFI variables between cold boots (e.g. VirtualBox before version 6.1) and anything set through the UEFI firmware interface is lost on poweroff.

The UEFI Shell Specification 2.0 establishes that a script called startup.nsh at the root of the ESP partition will always be interpreted and can contain arbitrary instructions; among those you can set a bootloading line. Make sure you mount the ESP partition on /boot and create a startup.nsh script that contains a kernel bootloading line. For example:

This method will work with almost all UEFI firmware versions you may encounter in real hardware, you can use it as last resort. The script must be a single long line. Sections in brackets are optional and given only as a guide. Shell style linebreaks are for visual clarification only. FAT filesystems use the backslash as path separator and in this case, the backslash declares the initramfs is located in the root of the ESP partition. Only Intel microcode is loaded in the booting parameters line; AMD microcode is read from disk later during the boot process; this is done automatically by the kernel.

Troubleshooting

Cannot create a new boot entry with efibootmgr

This article or section is a candidate for moving to Unified Extensible Firmware Interface#Troubleshooting.

Some kernel and efibootmgr version combinations might refuse to create new boot entries. This could be due to lack of free space in the NVRAM. You can try deleting any EFI dump files:

Or, as a last resort, boot with the efi_no_storage_paranoia kernel parameter. You can also try to downgrade your efibootmgr install to version 0.11.0. This version works with Linux version 4.0.6. See the bug discussion FS#34641, in particular the closing comment, for more information.

Newly created boot entries are removed

The factual accuracy of this article or section is disputed.

Some motherboards may remove boot entries after a couple of boots. This could be due to lack of free space in the NVRAM. To prevent this from occurring, it may help to reduce the amount of Linux boot entries being added by efibootmgr by minimizing your entry creation process, as well as reducing the amount of automatic drive boot entries by the Compatibility Support Module (CSM) by disabling it from your UEFI settings.

EFISTUB does not work on some Dell systems

Several generation Dell BIOSes are wrongly passing the arguments to the bootloader, thus making EFISTUB parse a null command line which normally means unbootable system (see the complete linux-efi thread).

A workaround has been found since Linux 5.10 to correct this behavior (see this commit ). For Linux See also

Источник

Unified Extensible Firmware Interface

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.

Contents

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 x86_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 (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, 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

• 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.

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:

Disable UEFI variable access

Access to the UEFI can potentially cause harm beyond the running OS level. Even hardware-level bricking is possible in some cases of poor UEFI implementation. [3]

So, as the UEFI variables access is not required for daily system usage, you may want to disable it, to avoid potential security breaches or accidental harm.

Possible solutions are:

• Mount efivars in read-only mode using fstab. For example:
• Use the noefi kernel parameter to completely disable OS access to UEFI.

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-gitAUR 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 .

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.

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.

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:\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:

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:

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 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

Remove UEFI boot support from optical media

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.

Using GRUB

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

• Create an editable USB flash installation medium.
• 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 ):

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:

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

Boot back to Arch Linux when stuck with Windows

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».

Enter firmware setup without function keys

On some laptops, like Lenovo XiaoXin 15are 2020, using keys like F2 or F12 does not do anything. This can possibly be fixed by returning laptops to OEM to repair mainboard information, but sometimes this is not possible or not desired. There are however other means to enter firmware setup:

• With systemctl: This will reboot your computer to firmware setup.
• With GRUB: Press c for command line and in GRUB command line use fwsetup to enter firmware setup.
• In Windows: Enter Advanced Startup, see #Boot back to Arch Linux when stuck with Windows.

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 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 ( \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 «» path «\EFI\path\to\app.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.
  3. Create a batch file with the command bcdedit /set «» DEFAULT » «
  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

Note: Windows 10 Home does not officially include gpedit.msc, although there are unsupported workarounds to install it manually.

• Alternatively, Task Scheduler can be used to run a startup script in Windows:
  1. Follow steps 1-3 above to create the batch file.
  2. Run taskschd.msc, then choose Create Task. from the Action menu.
  3. On the General tab: Enter any suitable Name and Description. Ensure the user account selected is an «Administrator», not a «Standard User». Select «Run whether user is logged in or not«. Select «Run with highest privileges«.
  4. On the Triggers tab, choose «At startup» from the menu, then click OK.
  5. On the Actions tab, click New. , then Browse. , and locate the batch file from step 1.
  6. On the Conditions tab, untick the Power options so the script runs when on battery power (for laptops).
  7. Click OK, and enter the password of the user account selected in step 4 when prompted.

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

Some firmware do not support custom boot entries. They will instead only boot from hardcoded boot entries.

A typical workaround is to not rely on boot entries in the NVRAM and install the boot loader to one of the common fallback paths on the EFI system partition.

The following sections describe the fallback paths.

Default boot path for removable drives

The UEFI specification defines default file paths for EFI binaries for booting from removable media. The relevant ones are:

• esp/EFI/BOOT/BOOTx64.EFI for x86_64 UEFI
• esp/EFI/BOOT/BOOTIA.EFI for IA32 UEFI.

While the specification defines these for removable drives only, most firmware support booting these from any drive.

See the appropriate boot loader article on how to install or migrate the boot loader to the default/fallback boot path.

Microsoft Windows boot loader location

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.

The factual accuracy of this article or section is disputed.

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:

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:

UEFI boot entry disappears after removing its referenced drive

Some firmware will remove boot entries referencing drives that are not present during boot. This could be an issue when frequently detaching/attaching drives or when booting from a removable drive.

Источник