Difference between revisions of "Unified Extensible Firmware Interface"

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[[ja:Unified Extensible Firmware Interface]]
 
[[ja:Unified Extensible Firmware Interface]]
 
[[ru:Unified Extensible Firmware Interface]]
 
[[ru:Unified Extensible Firmware Interface]]
[[zh-CN:Unified Extensible Firmware Interface]]
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[[zh-hans:Unified Extensible Firmware Interface]]
 
{{Related articles start}}
 
{{Related articles start}}
 
{{Related|Arch boot process}}
 
{{Related|Arch boot process}}
 
{{Related|Master Boot Record}}
 
{{Related|Master Boot Record}}
 +
{{Related|EFI System Partition}}
 
{{Related|GUID Partition Table}}
 
{{Related|GUID Partition Table}}
 +
{{Related|Secure Boot}}
 +
{{Related|UEFI/Hardware}}
 
{{Related articles end}}
 
{{Related articles end}}
 +
{{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.}}
  
'''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 [[Wikipedia:BIOS|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 24 July 2013, UEFI Specification 2.4 (released July 11, 2013) is the most recent version.
+
The [http://www.uefi.org/ Unified Extensible Firmware Interface] (EFI or UEFI 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|
+
It is distinct from the commonly used "[[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 [[Boot loaders]].
* This page explains '''What is UEFI''' and '''UEFI support in Linux kernel'''. It does not describe setting up UEFI Boot Loaders. For that information see [[Boot Loaders]].
 
* Unless specified as EFI 1.x, EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware. Also unless stated explicitly, these instructions are general and some of them may not work or may be different in Apple 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 (U)EFI specification and therefore is not a standard UEFI firmware.}}
 
  
== Differences between BIOS and UEFI ==
+
== UEFI versions ==
See [[Arch boot process#Firmware_types]] for more details.
+
* 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]].
  
== Boot Process under UEFI ==
+
The latest UEFI Specification can be found at http://uefi.org/specifications.
  
# System switched on - Power On Self Test, or POST process.
+
== UEFI firmware bitness ==
# UEFI firmware is loaded. Firmware initializes the hardware required for booting.
 
# Firmware then reads its Boot Manager data to determine which UEFI application to be launched and from where (i.e. from which disk and partition).
 
# Firmware then launches the UEFI application as defined in the boot entry in the firmware's boot manager.
 
# The launched 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 boot loader like GRUB) depending on how the UEFI application was configured.
 
  
{{Note|On some UEFI systems the only possible way to launch UEFI application on boot (if it does not have custom entry in UEFI boot menu) is to put it in this fixed location: {{ic|<EFI SYSTEM PARTITION>/EFI/boot/bootx64.efi}} (for 64-bit x86 system)}}
+
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 UEFI Application corresponding to the EFI firmware bitness/architecture.
  
=== Multibooting in UEFI ===
+
The vast majority of UEFI firmwares, including recent Apple Macs, use x86_64 EFI firmware. The only known devices that use IA32 (32-bit) EFI are older (pre 2008) Apple Macs, some Intel Cloverfield ultrabooks and some older Intel Server boards that are known to operate on Intel EFI 1.10 firmware.
  
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 [[Boot Loaders|boot loader]] to load another to switch OSes.
+
An x86_64 EFI firmware does not include support for launching 32-bit EFI apps (unlike x86_64 Linux and Windows versions which include such support). Therefore the UEFI application must be compiled for that specific firmware processor bitness/architecture.
  
==== Booting Microsoft Windows ====
+
=== Non Macs ===
 
 
64-bit Windows Vista (SP1+), Windows 7 and Windows 8 versions support booting using x86_64 EFI firmware. Windows forces type of partitioning depending on the firmware used, i.e. if Windows is booted in UEFI mode, it can be installed only to a GPT disk. If the Windows is booted in Legacy BIOS mode, it can be installed only to a MBR disk. This is a limitation enforced by Windows installer. Thus Windows supports either UEFI-GPT boot or BIOS-MBR boot only, not UEFI-MBR or BIOS-GPT boot.
 
 
 
Such a limitation is not enforced by the Linux kernel, but can depend on how the bootloader is configured. The Windows limitation should be considered if the user wishes to boot Windows and Linux from the same disk, since setting up the bootloader itself depends on the firmware type and disk partitioning used. In case where Windows and Linux dual boot from the same disk, it is advisable to follow the method used by Windows, either go for UEFI-GPT boot or BIOS-MBR boot only, not the other two cases.
 
 
 
32-bit Windows versions only support BIOS-MBR booting. So, in case of Linux and 32-bit Windows booting from the same disk, the disk has to use MBR. See http://support.microsoft.com/kb/2581408 for more info.
 
 
 
=== Detecting UEFI Firmware bitness ===
 
 
 
==== Non Macs ====
 
  
 
Check whether the dir {{ic|/sys/firmware/efi}} exists, if it exists it means the kernel has booted in EFI mode. In that case the UEFI bitness is same as kernel bitness. (ie. i686 or x86_64)
 
Check whether the dir {{ic|/sys/firmware/efi}} exists, if it exists it means the kernel has booted in EFI mode. In that case the UEFI bitness is same as kernel bitness. (ie. i686 or x86_64)
  
{{Note|Intel Atom System-on-Chip systems ship with 32-bit UEFI (as on 2 November 2013). See [[HCL/Firmwares/UEFI#Intel_Atom_System-on-Chip|this page]] for more info.}}
+
{{Note|Intel Atom System-on-Chip systems ship with 32-bit UEFI (as on 2 November 2013). See [[#Booting 64-bit kernel on 32-bit UEFI]] for more info. Also see [https://blogs.intel.com/evangelists/2015/07/22/why-cheap-systems-run-32-bit-uefi-on-x64-systems/ this Intel blog post].}}
  
==== Apple Macs ====
+
=== Apple Macs ===
  
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.  
+
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.
  
 
To find out the arch of the efi firmware in a Mac, type the following into the Mac OS X terminal:
 
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
+
  $ 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.
 
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.
  
=== Secure Boot ===
+
== Linux kernel config options for UEFI ==
For an overview about Secure Boot in Linux see http://www.rodsbooks.com/efi-bootloaders/secureboot.html. This section focuses on how to set up Secure Boot in Arch Linux. For the time being, this section is limited to explain the procedure of booting the archiso with Secure Boot enabled.
 
Booting the archiso with Secure Boot enabled is possible since the efi applications ''PreLoader.efi'' and ''HashTool.efi'' have been added to it. A message will show up that says ''Failed to Start loader... I will now execute HashTool.'' To use HashTool for enrolling the hash of ''loader.efi'' and ''vmlinuz.efi'', follow these steps.
 
* Select {{ic|OK}}
 
* In the HashTool main menu, select {{ic|Enroll Hash}}, choose {{ic|\loader.efi}} and confirm with {{ic|Yes}}. Again, select {{ic|Enroll Hash}} and {{ic|archiso}} to enter the archiso directory, then select {{ic|vmlinuz-efi}} and confirm with {{ic|Yes}}. Then choose {{ic|Exit}} to return to the boot device selection menu.
 
* In the boot device selection menu choose {{ic|Arch Linux archiso x86_64 UEFI CD}}
 
The archiso boots, and you are presented with a shell prompt, automatically logged in as root. To check if the archiso was booted with SecureBoot, use this command:
 
 
 
$ od -An -t u1 /sys/firmware/efi/vars/SecureBoot-1234abcde-5678-/data
 
 
 
If yes, this command returns 1. The characters denoted by 1234 differ from machine to machine. To help with this, you can use tab completion or list the efi variables.
 
 
 
== Linux Kernel Config options for UEFI ==
 
  
 
The required Linux Kernel configuration options for UEFI systems are :
 
The required Linux Kernel configuration options for UEFI systems are :
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  CONFIG_EFIVAR_FS=y
 
  CONFIG_EFIVAR_FS=y
  
UEFI Runtime Variables Support (old '''efivars sysfs''' interface - {{ic|/sys/firmware/efi/vars}}). This option should be disabled.
+
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.
  
 
  CONFIG_EFI_VARS=n
 
  CONFIG_EFI_VARS=n
Line 98: Line 77:
 
Retrieved from https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/Documentation/x86/x86_64/uefi.txt .
 
Retrieved from https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/Documentation/x86/x86_64/uefi.txt .
  
== UEFI Variables ==
+
== 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 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 -l
 
  $ efivar -l
  
=== UEFI Variables Support in Linux Kernel ===
+
=== UEFI variables support in Linux kernel ===
 
 
Linux kernel exposes EFI variables data to userspace via 2 interfaces:
 
  
* '''OLD sysfs-efivars''' interface (CONFIG_EFI_VARS) - populated by {{ic|efivars}} kernel module at {{ic|/sys/firmware/efi/vars}} - 1024 byte maximum per-variable data size limitation, no UEFI Secure Boot variables support (due to the size limitation) and not recommended by kernel upstream anymore. Still supported by kernel upstream but '''completely disabled in Arch's official kernels'''.
+
Linux kernel exposes EFI 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.
  
* '''NEW efivarfs''' ('''EFI''' '''VAR'''iable '''F'''ile'''S'''ystem) interface (CONFIG_EFIVAR_FS) - mounted using {{ic|efivarfs}} kernel module at {{ic|/sys/firmware/efi/efivars}} - replacement for the OLD sysfs-efivars interface, has no maximum per-variable size limitation, supports UEFI Secure Boot variables and recommended by kernel upstream. Introduced in kernel 3.8 and NEW {{ic|efivarfs}} module split from OLD {{ic|efivars}} kernel module in kernel 3.10 .
+
=== Requirements for UEFI variable support ===
 
 
==== Inconsistency between efivarfs and sysfs-efivars ====
 
 
 
Enabling both OLD sysfs-efivars and NEW efivarfs can cause data inconsistency issues (see See https://lkml.org/lkml/2013/4/16/473 for more info). Due to this OLD sysfs-efivars is completely disabled in Arch's official kernels (since '''core/{{Pkg|linux}}-3.11''' and '''core/{{Pkg|linux-lts}}-3.10''') and only NEW efivarfs is enabled/supported going forward. All the UEFI Variables related tools and utilities in [[official repositories]] support efivarfs as of 01 October 2013.
 
 
 
{{Note|As a side-effect of disabling OLD sysfs-efivars, {{ic|efi_pstore}} module is also disabled in the official Arch kernels as EFI pstore functionality in the kernel depends of OLD sysfs-efivars support.}}
 
 
 
If you have both interfaces enabled, you need to disable one of them, and disable and re-enable the other interface (to refresh the data, to prevent inconsistencies) before accessing the EFI VAR data using any userspace tool:
 
 
 
To disable sysfs-efivars and refresh efivarfs:
 
# modprobe -r efivars
 
 
# umount /sys/firmware/efi/efivars
 
# modprobe -r efivarfs
 
 
# modprobe efivarfs
 
# mount -t efivarfs efivarfs /sys/firmware/efi/efivars
 
 
 
To disable efivarfs and refresh sysfs-efivars:
 
# umount /sys/firmware/efi/efivars
 
# modprobe -r efivarfs
 
 
# modprobe -r efivars
 
# modprobe efivars
 
 
 
=== Requirements for UEFI Variables support to work properly ===
 
  
 +
# Kernel processor [[#UEFI firmware bitness|bitness]] and EFI processor bitness should match.
 +
# Kernel should be booted in EFI mode (via [[EFISTUB]] or any [[Boot loaders|EFI boot loader]], not via BIOS/CSM or Apple's "bootcamp" which is also BIOS/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 support should be present in the kernel ({{ic|1=CONFIG_EFI=y}}, check if present with {{ic|zgrep CONFIG_EFI /proc/config.gz}}).
# Kernel processor bitness/arch and EFI processor bitness/arch should match
+
# EFI Runtime Services in the kernel SHOULD NOT be disabled via kernel cmdline, i.e. {{ic|noefi}} kernel parameter SHOULD NOT be used.
# Kernel should be booted in EFI mode (via [[EFISTUB]] or any [[Boot Loaders|EFI boot loader]], not via BIOS/CSM or Apple's "bootcamp" which is also BIOS/CSM)
 
# 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|efivarfs}} filesystem should be mounted at {{ic|/sys/firmware/efi/efivars}}, otherwise follow [[#Mount efivarfs]] section below.
# {{ic|efivar}} should list (option {{ic|-l}}) the EFI Variables without any error. For sample output see [[#Sample_List_of_UEFI_Variables]].
+
# {{ic|efivar}} should list (option {{ic|-l}}) the EFI Variables without any error.
  
 
If EFI Variables support does not work even after the above conditions are satisfied, try the below workarounds:
 
If EFI Variables support does not work even after the above conditions are satisfied, try the below workarounds:
Line 153: Line 104:
 
==== Mount efivarfs ====
 
==== Mount efivarfs ====
  
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 Variable support to the userspace tools like {{ic|efibootmgr}} etc.:
+
{{Out of date|1=efivars is chattr +i since linux 4.5, see [https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0389075ecfb6231818de9b0225d3a5a21a661171]}}
 +
{{Warning|1=''efivars'' is mounted writeable by default [https://github.com/systemd/systemd/issues/2402], which may cause permanent damage to the system. [https://bbs.archlinux.org/viewtopic.php?id=207549]{{Dead link|2016|08|21}} As such, consider mounting ''efivars'' read-only ({{ic|-o ro}}) as described below. Note that when it is mounted read-only, tools such as ''efibootmgr'' and bootloaders will not be able to change boot settings, nor will commands like {{ic|systemctl reboot --firmware-setup}} work.}}
 +
 
 +
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]] like {{ic|efibootmgr}}:
  
 
  # mount -t efivarfs efivarfs /sys/firmware/efi/efivars
 
  # mount -t efivarfs efivarfs /sys/firmware/efi/efivars
  
{{Note|The above command should be run both OUTSIDE (BEFORE) and INSIDE '''chroot''', if any.}}
+
{{Note|The above command should be run both '''outside''' ('''before''') and '''inside''' the [[chroot]], if any.}}
  
It is also a good idea to auto-mount {{ic|efivarfs}} during boot via {{ic|/etc/fstab}} as follows:
+
To mount {{ic|efivarfs}} read-only during boot, add to {{ic|/etc/fstab}}:
  
{{hc|/etc/fstab|<nowiki>
+
{{hc|/etc/fstab|2=
efivarfs    /sys/firmware/efi/efivars    efivarfs    defaults    0   0
+
efivarfs    /sys/firmware/efi/efivars    efivarfs    '''ro''',nosuid,nodev,noexec,noatime 0 0
</nowiki>}}
+
}}
 +
 
 +
To remount with write support, run:
 +
 
 +
# mount -o remount /sys/firmware/efi/efivars -o '''rw''',nosuid,nodev,noexec,noatime
  
=== 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
  
# '''efivar''' - Library and Tool to manipulate UEFI Variables (used by vathpela's efibootmgr) - https://github.com/vathpela/efivar - {{Pkg|efivar}} or {{AUR|efivar-git}}
+
* {{App|efivar|Library and Tool to manipulate UEFI Variables (used by efibootmgr)|https://github.com/vathpela/efivar|{{Pkg|efivar}}, {{AUR|efivar-git}}}}
# '''efibootmgr''' - Tool to manipulate UEFI Firmware Boot Manager Settings. Upstream (http://linux.dell.com/git/efibootmgr.git) efibootmgr code does not support efivarfs. A fork of efibootmgr by Fedora's Peter Jones (vathpela) supports both efivarfs and sysfs-efivars. It is currently used in official core/{{Pkg|efibootmgr}} pkg and AUR pkg {{AUR|efibootmgr-pjones-git}} - https://github.com/vathpela/efibootmgr/tree/libefivars
+
* {{App|efibootmgr|Tool to manipulate UEFI Firmware Boot Manager Settings|https://github.com/vathpela/efibootmgr|{{Pkg|efibootmgr}}, {{AUR|efibootmgr-git}}{{Broken package link|package not found}}}}
# '''uefivars''' - Dumps list of EFI variables with some additional PCI related info (uses efibootmgr code internally) - https://github.com/fpmurphy/Various/tree/master/uefivars-2.0 supports only efivarfs and https://github.com/fpmurphy/Various/tree/master/uefivars-1.0 supports only sysfs-efivars . AUR package {{AUR|uefivars-git}}  
+
* {{App|uefivars|Dumps list of EFI variables with some additional PCI related info (uses efibootmgr code internally)|https://github.com/fpmurphy/Various/tree/master/uefivars-2.0|{{AUR|uefivars-git}}}}
# '''efitools''' - Tools to Create and Setup own UEFI Secure Boot Certificates, Keys and Signed Binaries (requires efivarfs) - {{AUR|efitools-git}}
+
* {{App|efitools|Tools for manipulating UEFI secure boot platforms|http://git.kernel.org/cgit/linux/kernel/git/jejb/efitools.git|{{Pkg|efitools}}, {{AUR|efitools-git}}{{Broken package link|package not found}}}}
# '''Ubuntu's Firmware Test Suite''' - https://wiki.ubuntu.com/FirmwareTestSuite/ - {{AUR|fwts}} (along with {{AUR|fwts-efi-runtime-dkms}}) or {{AUR|fwts-git}}
+
* {{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 ====
 
==== efibootmgr ====
  
{{Warning|
 
* Using {{ic|efibootmgr}} in Apple Macs may 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}}.}}
 
 
{{Note|
 
{{Note|
* If {{ic|efibootmgr}} completely fails to work in your system, you can reboot into UEFI Shell v2 and use {{ic|bcfg}} command to create a boot entry for the bootloader.
+
* 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 BIOSes allow users to directly manage uefi boot options from within the BIOS.  For example, some ASUS BIOSes have a "Add New Boot Option" choice which enables you to select a local EFI System Partition and manually enter the EFI stub location. (for example {{ic|\EFI\refind\refind_x64.efi}}).
+
* 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 ASUS 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 {{Pkg|refind-efi}} boot-loader as example.
+
* The below commands use [[rEFInd]] boot-loader as example.
 
}}
 
}}
  
Assuming the boot-loader file to be launched is {{ic|/boot/efi/EFI/refind/refind_x64.efi}}, {{ic|/boot/efi/EFI/refind/refind_x64.efi}} can be split up as {{ic|/boot/efi}} and {{ic|/EFI/refind/refind_x64.efi}}, wherein {{ic|/boot/efi}} is the mountpoint of the EFI System Partition, which is assumed to be {{ic|/dev/sdXY}} (here {{ic|X}} and {{ic|Y}} are just placeholders for the actual values - eg:- in {{ic|/dev/sda1}} , {{ic|1=X==a}} {{ic|1=Y==1}}).
+
To add a new boot option using ''efibootmgr'' you need to know three things:
  
To determine the actual device path for the EFI System Partition (assuming mountpoint {{ic|/boot/efi}} for example) (should be in the form {{ic|/dev/sdXY}}), try :
+
# The disk containing the EFI System Partition (ESP): {{ic|/dev/sd''X''}}
 +
# The partition number of the ESP on that disk: the {{ic|''Y''}} in {{ic|/dev/sdX''Y''}}
 +
# The path to the UEFI application (relative to the root of the ESP)
  
# findmnt /boot/efi
+
For example, if you want to add a boot option for {{ic|/boot/efi/EFI/refind/refind_x64.efi}} where {{ic|/boot/efi}} is the mount point of the ESP, run
TARGET SOURCE  FSTYPE OPTIONS
 
/boot/efi /dev/sdXY  vfat        rw,flush,tz=UTC
 
  
Verify that uefi variables support in kernel is working properly by running:
+
{{hc|$ findmnt /boot/efi|2=
 
+
TARGET    SOURCE    FSTYPE OPTIONS
# efivar -l
+
/boot/efi /dev/sda1  vfat  rw,flush,tz=UTC
 
 
If efivar lists the uefi variables without any error, then you can proceed. If not, check whether all the conditions in [[#Requirements for UEFI Variables support to work properly]] are met.
 
 
 
Then create the boot entry using efibootmgr as follows:
 
 
 
# efibootmgr -c -d /dev/sdX -p Y -l /EFI/refind/refind_x64.efi -L "rEFInd"
 
 
 
{{Note|1=UEFI uses backward slash {{ic|\}} as path separator (similar to Windows paths), but the official {{Pkg|efibootmgr}} pkg support passing unix-style paths with forward-slash {{ic|/}} as path-separator for the {{ic|-l}} option. Efibootmgr internally converts {{ic|/}} to {{ic|\}} before encoding the loader path. The relevant git commit that incorporated this feature in efibootmgr is http://linux.dell.com/cgi-bin/cgit.cgi/efibootmgr.git/commit/?id=f38f4aaad1dfa677918e417c9faa6e3286411378 .}}
 
 
 
In the above command {{ic|/boot/efi/EFI/refind/refind_x64.efi}} translates to {{ic|/boot/efi}} and {{ic|/EFI/refind/refind_x64.efi}} which in turn translate to drive {{ic|/dev/sdX}} -> partition {{ic|Y}} -> file {{ic|/EFI/refind/refind_x64.efi}}.
 
 
 
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/cgit.cgi/efibootmgr.git/plain/README efibootmgr GIT README] .
 
 
 
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\refind\refindx64.efi}} or {{ic|\efi\refind\refind_x64.efi}} does not matter (this will change if the filesystem encoding is UTF-8).
 
 
 
== EFI System Partition ==
 
 
 
The EFI System Partition (also called ESP or EFISYS) is a FAT32 formatted physical partition (in the main partition table of the disk, not LVM or software raid etc.) from where the UEFI firmware launches the UEFI bootloader and application. It is a OS independent partition that acts as the storage place for the EFI bootloaders and applications which the firmware launches them. It is mandatory for UEFI boot. It should be marked as '''EF00''' or '''ef00''' type code in gdisk, or '''boot''' flag in case of GNU Parted (only for GPT disk). It is recommended to keep ESP size at 512 MiB although smaller/larger sizes are fine (smaller sizes provided it is higher than the minimum FAT32 FS partition size limit (as mandated by FAT32 specification from Microsoft). For more info visit [[Wikipedia:EFI_System_partition|link]].
 
 
 
{{Note|
 
* It is recommended to use always GPT for UEFI boot as some UEFI firmwares do not allow UEFI-MBR boot.
 
* In GNU Parted, {{ic|boot}} flag (not to be confused with {{ic|legacy_boot}} flag) has different effect in MBR and GPT disk. In MBR disk, it marks the partition as active. In GPT disk, it changes the type code of the partition to {{ic|EFI System Partition}} type. Parted has no flag to mark a partition as ESP in MBR disk (this can be done using fdisk though).
 
* Microsoft documentation noted the ESP size: For Advanced Format 4K Native drives (4-KB-per-sector) drives, the minimum size is 260 MB, due to a limitation of the FAT32 file format. The minimum partition size of FAT32 drives is calculated as sector size (4KB) x 65527 &#61; 256 MB. Advanced Format 512e drives are not affected by this limitation, because their emulated sector size is 512 bytes. 512 bytes x 65527 &#61; 32 MB, which is less than the 100 MB minimum size for this partition. From: http://technet.microsoft.com/en-us/library/hh824839.aspx#DiskPartitionRules
 
* In case of [[EFISTUB]], the kernels and initramfs files should be stored in the EFI System Partition. For sake of simplicity, you can also use the ESP as the {{ic|/boot}} partition itself instead of a separate {{ic|/boot}} partition, for EFISTUB booting.
 
 
}}
 
}}
  
=== GPT partitioned disks ===
+
In this example, this indicates that the ESP is on disk {{ic|/dev/sda}} and has partition number 1. The path to the UEFI application relative to the root of the ESP is {{ic|/EFI/refind/refind_x64.efi}}. So you would create the boot entry as follows:
 
 
* Create a partition with partition type {{ic|ef00}} or {{ic|EF00}} using gdisk (from {{Pkg|gptfdisk}} pkg). Then format that partition as FAT32 using {{ic|mkfs.fat -F32 /dev/<THAT_PARTITION>}}  
 
(or)
 
* Create a FAT32 partition and in GNU Parted set/activate the {{ic|boot}} flag (not {{ic|legacy_boot}} flag) on that partition
 
  
{{Note|If you get the message {{ic|WARNING: Not enough clusters for a 32 bit FAT!}}, reduce cluster size with {{ic|mkfs.fat -s2 -F32 ...}} or {{ic|-s1}}, otherwise the partition may be unreadable by UEFI.}}
+
# efibootmgr --create --disk /dev/sda --part 1 --loader /EFI/refind/refind_x64.efi --label "rEFInd Boot Manager"
  
=== MBR partitioned disks ===
+
See {{man|8|efibootmgr}} or [https://raw.githubusercontent.com/rhinstaller/efibootmgr/master/README efibootmgr README] for more info.
  
Create a partition with partition type {{ic|0xEF}} using fdisk (from {{Pkg|util-linux}} pkg). Then format that partition as FAT32 using {{ic|mkfs.fat -F32 /dev/<THAT_PARTITION>}}
+
{{Note|1=UEFI uses backward slash {{ic|\}} as path separator but ''efibootmgr'' automatically converts UNIX-style {{ic|/}} path separators.}}
  
 
== UEFI Shell ==
 
== UEFI Shell ==
  
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.  
+
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.
  
 
=== Obtaining UEFI Shell ===
 
=== Obtaining UEFI Shell ===
  
You can download a BSD licensed UEFI Shell from Intel's Tianocore UDK/EDK2 Sourceforge.net project.
+
You can download a BSD licensed UEFI Shell from Intel's Tianocore UDK/EDK2 Sourceforge.net project:
 +
* [[AUR]] package {{AUR|uefi-shell-git}} (recommended) - provides x86_64 Shell in x86_64 system and IA32 Shell in i686 system - compiled directly from latest Tianocore EDK2 SVN 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/tree/master/ShellBinPkg Precompiled UEFI Shell v2 binaries] (may not be up-to-date)
 +
* [https://github.com/tianocore/edk2/tree/master/EdkShellBinPkg Precompiled UEFI Shell v1 binaries] (not updated anymore upstream)
 +
* [http://dl.dropbox.com/u/17629062/Shell2.zip Precompiled UEFI Shell v2 binary with bcfg modified to work with UEFI pre-2.3 firmware] - from Clover EFI bootloader
  
* [[AUR]] '''{{AUR|uefi-shell-svn}}''' pkg (recommended) - provides x86_64 Shell in x86_64 system and IA32 Shell in i686 system - compiled directly from latest Tianocore EDK2 SVN source
+
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 [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=ShellPkg ShellPkg] and [http://sourceforge.net/mailarchive/message.php?msg_id=28690732 this mail]{{Dead link|2016|08|21}}
* [https://svn.code.sf.net/p/edk2/code/trunk/edk2/ShellBinPkg/UefiShell/X64/Shell.efi Precompiled x86_64 UEFI Shell v2 binary] (may not be up-to-date)
 
* [https://svn.code.sf.net/p/edk2/code/trunk/edk2/EdkShellBinPkg/FullShell/X64/Shell_Full.efi Precompiled x86_64 UEFI Shell v1 binary] (not updated anymore upstream)
 
* [https://svn.code.sf.net/p/edk2/code/trunk/edk2/ShellBinPkg/UefiShell/Ia32/Shell.efi Precompiled IA32 UEFI Shell v2 binary] (may not be up-to-date)
 
* [https://svn.code.sf.net/p/edk2/code/trunk/edk2/EdkShellBinPkg/FullShell/Ia32/Shell_Full.efi Precompiled IA32 UEFI Shell v1 binary] (not updated anymore upstream)
 
 
 
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 [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=ShellPkg ShellPkg] and [http://sourceforge.net/mailarchive/message.php?msg_id=28690732 this mail]
 
  
 
=== Launching UEFI Shell ===
 
=== Launching UEFI Shell ===
Line 258: Line 185:
 
{{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.}}
 
{{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.}}
  
=== Important UEFI Shell Commands ===
+
=== Important UEFI Shell commands ===
  
UEFI Shell commands usually support {{ic|-b}} option which makes output pause after each page. {{ic|map}} lists recognized filesystems ({{ic|fs0}}, ...) and data storage devices ({{ic|blk0}}, ...). Run {{ic|help -b}} to list available commands.
+
UEFI Shell commands usually support {{ic|-b}} option which makes output pause after each page. Run {{ic|help -b}} to list available commands.
  
 
More info at http://software.intel.com/en-us/articles/efi-shells-and-scripting/
 
More info at http://software.intel.com/en-us/articles/efi-shells-and-scripting/
Line 266: Line 193:
 
==== bcfg ====
 
==== bcfg ====
  
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.
+
{{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 [http://www.uefi.org/sites/default/files/resources/UEFI_Shell_Spec_2_0.pdf UEFI Shell Specification 2.0] document.
  
 
{{Note|
 
{{Note|
* Users are recommended to try {{ic|bcfg}} only if {{ic|efibootmgr}} fails to create working boot entries in their system.
+
* 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. You can download a [http://dl.dropbox.com/u/17629062/Shell2.zip modified UEFI Shell v2 binary] which may work in UEFI pre-2.3 firmwares.
+
* 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.
 
}}
 
}}
  
Line 282: Line 209:
  
 
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.
 
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.
 +
 +
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]]:
 +
 +
Shell> bcfg boot add '''N''' fs'''V''':\vmlinuz-linux "Arch Linux"
 +
Shell> bcfg boot -opt '''N''' "root='''/dev/sdX#''' initrd=\initramfs-linux.img"
 +
 +
where {{ic|N}} is the priority, {{ic|V}} is the volume number of your EFI partition, and {{ic|/dev/sdX#}} is your root partition.
  
 
To remove the 4th boot option:
 
To remove the 4th boot option:
Line 298: Line 232:
  
 
  Shell> bcfg -? -v -b
 
  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}}).
 +
 +
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:
 +
 +
Shell> fs0:
 +
fs0:\> cd EFI/
  
 
==== edit ====
 
==== edit ====
  
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.
+
{{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.
  
To edit, for example rEFInd's {{ic|refind.conf}} in the EFI System Partition ({{ic|fs0:}} in the firmware)
+
For example, to edit rEFInd's {{ic|refind.conf}} in the EFI System Partition ({{ic|fs0:}} in the firmware),
  
  Shell> fs0:
+
  Shell> edit FS0:\EFI\refind\refind.conf
FS0:\> cd \EFI\arch\refind
 
FS0:\EFI\arch\refind\> edit refind.conf
 
  
 
Type {{ic|Ctrl-E}} for help.
 
Type {{ic|Ctrl-E}} for help.
  
== UEFI Linux Hardware Compatibility ==
+
== UEFI Linux hardware compatibility ==
  
See [[HCL/Firmwares/UEFI]] for the main article.
+
See [[Unified Extensible Firmware Interface/Hardware]] for more information.
  
 
== UEFI Bootable Media ==
 
== UEFI Bootable Media ==
Line 319: Line 260:
 
=== Create UEFI bootable USB from ISO ===
 
=== Create UEFI bootable USB from ISO ===
  
Follow [[USB Flash Installation Media#BIOS and UEFI Bootable USB]]
+
Follow [[USB flash installation media#BIOS and UEFI bootable USB]]
  
=== Remove UEFI boot support from Optical Media ===
+
=== 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.}}
 
{{Note|This section mentions removing UEFI boot support from a '''CD/DVD only''' (Optical Media), not from a USB flash drive.}}
Line 331: Line 272:
 
  # mount -o loop ''input.iso'' /mnt/iso
 
  # mount -o loop ''input.iso'' /mnt/iso
  
* Then rebuild the ISO, excluding the UEFI Optical Media booting support, using {{ic|xorriso}} from {{pkg|libisoburn}}
+
* 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:
 
{{bc|1=
 
{{bc|1=
 
$ xorriso -as mkisofs -iso-level 3 \
 
$ xorriso -as mkisofs -iso-level 3 \
Line 350: Line 291:
 
== Testing UEFI in systems without native support ==
 
== Testing UEFI in systems without native support ==
  
=== OVMF for Virtual Machines ===
+
=== OVMF for virtual machines ===
  
OVMF [http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=OVMF] is a tianocore project to enable UEFI support for Virtual Machines. OVMF contains a sample UEFI firmware for QEMU.
+
[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.
  
You can build OVMF (with Secure Boot support) from AUR {{AUR|ovmf-svn}} and run it as follows:
+
You can install {{pkg|ovmf}} from the extra repository.
  
  $ qemu-system-x86_64 -enable-kvm -net none -m 1024 -bios /usr/share/ovmf/x86_64/bios.bin  
+
It is [http://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 /usr/share/ovmf/ovmf_vars_x64.bin 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/ovmf_code_x64.bin \
 +
-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/ovmf_code_x64.bin -drive if=pflash,format=raw,file=efi_vars.bin
  
 
=== DUET for BIOS only systems ===
 
=== DUET for BIOS only systems ===
  
DUET is a tianocore project that enables chainloading a full UEFI environment from a BIOS system, in a way similar to BIOS OS booting. This method is being discussed extensively in http://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://gitorious.org/tianocore_uefi_duet_builds. Specific instructions for setting up DUET is available at https://gitorious.org/tianocore_uefi_duet_builds/tianocore_uefi_duet_installer/blobs/raw/master/Migle_BootDuet_INSTALL.txt.  
+
DUET is a tianocore project that enables chainloading a full UEFI environment from a BIOS system, in a way similar to BIOS OS booting. This method is being discussed extensively in http://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 .
  
 
You can also try http://sourceforge.net/projects/cloverefiboot/ which provides modified DUET images that may contain some system specific fixes and is more frequently updated compared to the gitorious repos.
 
You can also try http://sourceforge.net/projects/cloverefiboot/ which provides modified DUET images that may contain some system specific fixes and is more frequently updated compared to the gitorious repos.
Line 366: Line 318:
 
== Troubleshooting ==
 
== Troubleshooting ==
  
=== Windows 7 will not boot in UEFI Mode ===
+
=== Windows 7 will not boot in UEFI mode ===
  
If you have installed Windows to a different harddisk with GPT partitioning and still have a MBR partitioned harddisk in your computer, then it is possible that the UEFI BIOS is starting it's CSM support (for booting MBR partitions) and therefor Windows will not boot. To solve this merge your MBR harddisk to GPT partitioning or disable the SATA port where the MBR harddisk is plugged in or unplug the SATA connector from this harddisk.
+
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:
 
Mainboards with this kind of problem:
  
Gigabyte Z77X-UD3H rev. 1.1 (UEFI BIOS version F19e)
+
* 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 ===
  
- UEFI BIOS option for booting UEFI Only does not pretend the UEFI BIOS from starting CSM
+
If you [[dual boot with Windows]] and your motherboard just boots Windows immediately instead of your chosen UEFI application, there are several possible causes and workarounds.
 +
 
 +
* 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 UEFI 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 UEFI 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
  
 
=== USB media gets struck with black screen ===
 
=== USB media gets struck with black screen ===
  
* This issue can occur either due to [[KMS]] issue. Try [[Kernel_Mode_Setting#Disabling_modesetting|Disabling KMS]] while booting the USB.
+
This issue can occur due to [[KMS]] issue. Try [[Kernel mode setting#Disabling_modesetting|Disabling KMS]] while booting the USB.
  
* If the issue is not due to KMS, then it may be due to bug in [[EFISTUB]] booting (see [https://bugs.archlinux.org/task/33745] and [https://bbs.archlinux.org/viewtopic.php?id=156670] for more information.). Both Official ISO ([[Archiso]]) and [[Archboot]] iso use EFISTUB (via [[Gummiboot]] Boot Manager for menu) for booting the kernel in UEFI mode. In such a case you have to use [[GRUB]] as the USB's UEFI bootloader by following the below section.
+
=== Booting 64-bit kernel on 32-bit UEFI ===
 +
 
 +
Both Official ISO ([[Archiso]]) and [[Archboot]] iso use EFISTUB (via [[systemd-boot]] Boot Manager for menu) for booting the kernel in UEFI mode. To boot 64-bit kernel with 32-bit UEFI you have to use [[GRUB]] as the USB's UEFI bootloader by following the below section.
  
 
==== Using GRUB ====
 
==== Using GRUB ====
 +
{{Tip|The given configuration entries can also be entered inside a [[GRUB#Using_the_command_shell|GRUB command-shell]].}}
  
* Create USB Flash Installation drive as mentioned in [[USB_Flash_Installation_Media#BIOS_and_UEFI_Bootable_USB|link]]. After that follow the below steps to use GRUB instead of Gummiboot.
+
* [[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
  
* Backup {{ic|<USB>/EFI/boot/loader.efi}} to {{ic|<USB>/EFI/boot/gummiboot.efi}}
+
* Backup {{ic|EFI/boot/loader.efi}} to {{ic|EFI/boot/gummiboot.efi}}
  
* [[GRUB#GRUB_Standalone|Create a GRUB standalone image]] and copy it to {{ic|<USB>/EFI/boot/loader.efi}}
+
* [[GRUB/Tips and tricks#GRUB standalone|Create a GRUB standalone image]] for i686 system and copy the generated {{ic|grub*.efi}} to the USB as {{ic|EFI/boot/loader.efi}} and/or {{ic|EFI/boot/bootia32.efi}}
  
* Create {{ic|<USB>/EFI/boot/grub.cfg}} with the following contents:
+
* Create {{ic|EFI/boot/grub.cfg}} with the following contents (replace {{ic|ARCH_YYYYMM}} with the required archiso label e.g. {{ic|ARCH_201507}}):
  
{{hc|grub.cfg for Official ISO|<nowiki>
+
{{hc|grub.cfg for official ISO|<nowiki>
 
insmod part_gpt
 
insmod part_gpt
 
insmod part_msdos
 
insmod part_msdos
Line 413: Line 383:
 
menuentry "Arch Linux archiso x86_64" {
 
menuentry "Arch Linux archiso x86_64" {
 
     set gfxpayload=keep
 
     set gfxpayload=keep
     search --no-floppy --set=root --label ARCHISO_XXXXXX
+
     search --no-floppy --set=root --label ARCH_YYYYMM
     linux /arch/boot/x86_64/vmlinuz archisobasedir=arch archisolabel=ARCHISO_XXXXXX add_efi_memmap
+
     linux /arch/boot/x86_64/vmlinuz archisobasedir=arch archisolabel=ARCH_YYYYMM add_efi_memmap
 
     initrd /arch/boot/x86_64/archiso.img
 
     initrd /arch/boot/x86_64/archiso.img
 
}
 
}
  
 
menuentry "UEFI Shell x86_64 v2" {
 
menuentry "UEFI Shell x86_64 v2" {
     search --no-floppy --set=root --label ARCHISO_XXXXXX
+
     search --no-floppy --set=root --label ARCH_YYYYMM
 
     chainloader /EFI/shellx64_v2.efi
 
     chainloader /EFI/shellx64_v2.efi
 
}
 
}
   
+
 
 
menuentry "UEFI Shell x86_64 v1" {
 
menuentry "UEFI Shell x86_64 v1" {
     search --no-floppy --set=root --label ARCHISO_XXXXXX
+
     search --no-floppy --set=root --label ARCH_YYYYMM
 
     chainloader /EFI/shellx64_v1.efi
 
     chainloader /EFI/shellx64_v1.efi
 
}
 
}
Line 459: Line 429:
 
     chainloader /EFI/tools/shellx64_v2.efi
 
     chainloader /EFI/tools/shellx64_v2.efi
 
}
 
}
   
+
 
 
menuentry "UEFI Shell x86_64 v1" {
 
menuentry "UEFI Shell x86_64 v1" {
 
     search --no-floppy --set=root --file /boot/vmlinuz_x86_64
 
     search --no-floppy --set=root --file /boot/vmlinuz_x86_64
Line 465: Line 435:
 
}
 
}
 
</nowiki>}}
 
</nowiki>}}
 +
 +
=== 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 {{ic|efibootmgr}} or {{ic|bcfg}} from the EFI 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 {{ic|.efi}} file in the location that Windows uses.
 +
 +
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:
 +
 +
FS1:
 +
cd EFI
 +
mkdir Microsoft
 +
cd Microsoft
 +
mkdir Boot
 +
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 ==
 
== See also ==
  
 
* [[Wikipedia:UEFI]]
 
* [[Wikipedia:UEFI]]
* [[Wikipedia:EFI System partition]]
+
* [http://www.uefi.org/home/ UEFI Forum] - contains the official [http://uefi.org/specifications UEFI Specifications] - GUID Partition Table is part of UEFI Specification
 
* [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]
 
* [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]
 
* [https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/Documentation/x86/x86_64/uefi.txt Linux Kernel x86_64 UEFI Documentation]
 
* [https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/Documentation/x86/x86_64/uefi.txt Linux Kernel x86_64 UEFI Documentation]
* [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
+
* [http://www.intel.com/technology/efi/ Intel's page on EFI]{{Dead link|2016|07|16}}
 +
* [http://firmware.intel.com/ Intel Architecture Firmware Resource Center]
 +
* [http://firmware.intel.com/blog/linux-efi-boot-stub Matt Fleming - The Linux EFI Boot Stub]
 +
* [http://firmware.intel.com/blog/accessing-uefi-variables-linux Matt Fleming - Accessing UEFI Variables from Linux]
 +
* [http://www.rodsbooks.com/linux-uefi/ Rod Smith - Linux on UEFI: A Quick Installation Guide]
 +
* [https://lkml.org/lkml/2011/6/8/322 UEFI Boot problems on some newer machines (LKML)]
 +
* [http://linuxplumbers.ubicast.tv/videos/plumbing-uefi-into-linux/ LPC 2012 Plumbing UEFI into Linux]
 +
* [http://linuxplumbers.ubicast.tv/videos/uefi-tutorial-part-1/ LPC 2012 UEFI Tutorial : part 1]
 +
* [http://linuxplumbers.ubicast.tv/videos/uefi-tutorial-part-2/ LPC 2012 UEFI Tutorial : part 2]
 
* [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
 
* [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
* [http://uefidk.intel.com/ Intel UEFI Community Resource Center]
+
* [https://jdebp.eu/FGA/efi-boot-process.html FGA: The EFI boot process]
* [http://www.intel.com/technology/efi/ Intel's page on EFI]
+
* [http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx Microsoft's Windows and GPT FAQ]
* [http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/efi-boot-process.html FGA: The EFI boot process]
+
* [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]
* [http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx Microsoft's Windows and GPT FAQ] - Contains info on Windows UEFI booting also
+
* [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://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://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]
 
* [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)]
 
 
* [http://software.intel.com/en-us/articles/efi-shells-and-scripting/ EFI Shells and Scripting - Intel Documentation]
 
* [http://software.intel.com/en-us/articles/efi-shells-and-scripting/ EFI Shells and Scripting - Intel Documentation]
 
* [http://software.intel.com/en-us/articles/uefi-shell/ UEFI Shell  - Intel Documentation]
 
* [http://software.intel.com/en-us/articles/uefi-shell/ UEFI Shell  - Intel Documentation]
 
* [http://www.hpuxtips.es/?q=node/293 UEFI Shell - bcfg command info]
 
* [http://www.hpuxtips.es/?q=node/293 UEFI Shell - bcfg command info]
* [http://dl.dropbox.com/u/17629062/Shell2.zip UEFI Shell v2 binary with bcfg modified to work with UEFI pre-2.3 firmware - from Clover efiboot]
 
* [http://linuxplumbers.ubicast.tv/videos/plumbing-uefi-into-linux/ LPC 2012 Plumbing UEFI into Linux]
 
* [http://linuxplumbers.ubicast.tv/videos/uefi-tutorial-part-1/ LPC 2012 UEFI Tutorial : part 1]
 
* [http://linuxplumbers.ubicast.tv/videos/uefi-tutorial-part-2/ LPC 2012 UEFI Tutorial : part 2]
 

Latest revision as of 11:08, 3 December 2017

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 (EFI or UEFI 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 Boot loaders.

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 http://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 UEFI Application corresponding to the EFI firmware bitness/architecture.

The vast majority of UEFI firmwares, including recent Apple Macs, use x86_64 EFI firmware. The only known devices that use IA32 (32-bit) EFI are older (pre 2008) Apple Macs, some Intel Cloverfield ultrabooks and some older Intel Server boards that are known to operate on Intel EFI 1.10 firmware.

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

Non Macs

Check whether the dir /sys/firmware/efi exists, if it exists it means the kernel has booted in EFI mode. In that case the UEFI bitness is same as kernel bitness. (ie. i686 or x86_64)

Note: Intel Atom System-on-Chip systems ship with 32-bit UEFI (as on 2 November 2013). See #Booting 64-bit kernel on 32-bit UEFI for more info. Also see this Intel blog post.

Apple Macs

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.

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.

Linux kernel config options for UEFI

The required Linux Kernel configuration options for UEFI systems are :

CONFIG_RELOCATABLE=y
CONFIG_EFI=y
CONFIG_EFI_STUB=y
CONFIG_FB_EFI=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
Note: All of the above options are required to boot Linux via UEFI, and are enabled in Archlinux kernels in official repos.

Retrieved from https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/Documentation/x86/x86_64/uefi.txt .

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 -l

UEFI variables support in Linux kernel

Linux kernel exposes EFI 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 processor bitness and EFI processor bitness should match.
  2. Kernel should be booted in EFI mode (via EFISTUB or any EFI boot loader, not via BIOS/CSM or Apple's "bootcamp" which is also BIOS/CSM).
  3. EFI Runtime Services support should be present in the kernel (CONFIG_EFI=y, check if present with zgrep CONFIG_EFI /proc/config.gz).
  4. EFI Runtime Services in the kernel SHOULD NOT be disabled via kernel cmdline, i.e. noefi kernel parameter SHOULD NOT be used.
  5. efivarfs filesystem should be mounted at /sys/firmware/efi/efivars, otherwise follow #Mount efivarfs section below.
  6. efivar should list (option -l) the EFI Variables without any error.

If EFI 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 efi variables 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 efi variable storage space check that may prevent writing/modification of efi variables.
Note: 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.

Mount efivarfs

Tango-view-refresh-red.pngThis article or section is out of date.Tango-view-refresh-red.png

Reason: efivars is chattr +i since linux 4.5, see [1] (Discuss in Talk:Unified Extensible Firmware Interface#)
Warning: efivars is mounted writeable by default [2], which may cause permanent damage to the system. [3][dead link 2016-08-21] As such, consider mounting efivars read-only (-o ro) as described below. Note that when it is mounted read-only, tools such as efibootmgr and bootloaders will not be able to change boot settings, nor will commands like systemctl reboot --firmware-setup work.

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.

To mount efivarfs read-only during boot, add to /etc/fstab:

/etc/fstab
efivarfs    /sys/firmware/efi/efivars    efivarfs    ro,nosuid,nodev,noexec,noatime 0 0

To remount with write support, run:

# mount -o remount /sys/firmware/efi/efivars -o rw,nosuid,nodev,noexec,noatime

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/vathpela/efivar || efivar, efivar-gitAUR
  • efibootmgr — Tool to manipulate UEFI Firmware Boot Manager Settings
https://github.com/vathpela/efibootmgr || efibootmgr, efibootmgr-gitAUR[broken link: package not found]
  • uefivars — Dumps list of EFI 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
http://git.kernel.org/cgit/linux/kernel/git/jejb/efitools.git || efitools, efitools-gitAUR[broken link: package not found]
  • Ubuntu's Firmware Test Suite — Test suite that performs sanity checks on Intel/AMD PC firmware
https://wiki.ubuntu.com/FirmwareTestSuite/ || fwts-gitAUR

efibootmgr

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 ASUS 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-loader 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): /dev/sdX
  2. The partition number of the ESP on that disk: the Y in /dev/sdXY
  3. The path to the UEFI application (relative to the root of the ESP)

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

$ findmnt /boot/efi
TARGET    SOURCE     FSTYPE OPTIONS
/boot/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 UEFI 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"

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 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.

Obtaining UEFI Shell

You can download a BSD licensed UEFI Shell from Intel's Tianocore UDK/EDK2 Sourceforge.net 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[dead link 2016-08-21]

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 (mostly /boot/efi/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 commands.

More info at http://software.intel.com/en-us/articles/efi-shells-and-scripting/

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 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 Linux hardware compatibility

See Unified Extensible Firmware Interface/Hardware for more information.

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.

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/ovmf_vars_x64.bin 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/ovmf_code_x64.bin \
-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/ovmf_code_x64.bin -drive if=pflash,format=raw,file=efi_vars.bin …

DUET for BIOS only systems

DUET is a tianocore project that enables chainloading a full UEFI environment from a BIOS system, in a way similar to BIOS OS booting. This method is being discussed extensively in http://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 .

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

Booting 64-bit kernel on 32-bit UEFI

Both Official ISO (Archiso) and Archboot iso use EFISTUB (via systemd-boot Boot Manager for menu) for booting the kernel in UEFI mode. To boot 64-bit kernel with 32-bit UEFI you have to use GRUB as the USB's UEFI bootloader by following the below section.

Using GRUB

Tip: The given configuration entries can also be entered inside a GRUB command-shell.
  • Backup EFI/boot/loader.efi to EFI/boot/gummiboot.efi
  • Create EFI/boot/grub.cfg with the following contents (replace ARCH_YYYYMM with the required archiso label e.g. ARCH_201507):
grub.cfg for official ISO
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" {
    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/x86_64/archiso.img
}

menuentry "UEFI Shell x86_64 v2" {
    search --no-floppy --set=root --label ARCH_YYYYMM
    chainloader /EFI/shellx64_v2.efi
}

menuentry "UEFI Shell x86_64 v1" {
    search --no-floppy --set=root --label ARCH_YYYYMM
    chainloader /EFI/shellx64_v1.efi
}
grub.cfg for Archboot ISO
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 x86_64 Archboot" {
    set gfxpayload=keep
    search --no-floppy --set=root --file /boot/vmlinuz_x86_64
    linux /boot/vmlinuz_x86_64 cgroup_disable=memory loglevel=7 add_efi_memmap
    initrd /boot/initramfs_x86_64.img
}

menuentry "UEFI Shell x86_64 v2" {
    search --no-floppy --set=root --file /boot/vmlinuz_x86_64
    chainloader /EFI/tools/shellx64_v2.efi
}

menuentry "UEFI Shell x86_64 v1" {
    search --no-floppy --set=root --file /boot/vmlinuz_x86_64
    chainloader /EFI/tools/shellx64_v1.efi
}

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 EFI 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:

FS1:
cd EFI
mkdir Microsoft
cd Microsoft
mkdir Boot
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