Difference between revisions of "Unified Extensible Firmware Interface"

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[[ru:Unified Extensible Firmware Interface]]
 
[[ru:Unified Extensible Firmware Interface]]
 
[[zh-CN:Unified Extensible Firmware Interface]]
 
[[zh-CN:Unified Extensible Firmware Interface]]
{{Article summary start}}
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{{Related articles start}}
{{Article summary text|An overview of the Unified Extensible Firmware Interface.}}
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{{Related|Arch boot process}}
{{Article summary heading|Overview}}
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{{Related|Master Boot Record}}
{{Article summary text|{{Boot process overview}}}}
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{{Related|EFI System Partition}}
{{Article summary heading|Related}}
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{{Related|GUID Partition Table}}
{{Article summary wiki|GUID Partition Table}}
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{{Related|UEFI/Hardware}}
{{Article summary wiki|Master Boot Record}}
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{{Related articles end}}
{{Article summary wiki|Arch Boot Process}}
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{{Warning|While the choice to install in UEFI mode is forward looking, early vendor UEFI implementations may carry more bugs than their BIOS counterparts. It is advised to do a search relating to your particular mainboard model before proceeding.}}
{{Article summary end}}
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'''Unified Extensible Firmware Interface''' (or UEFI for short) is a new type of firmware that was initially designed by Intel (known as EFI then) mainly for its Itanium based systems. It introduces new ways of booting an OS that is distinct from the commonly used "MBR boot code" method followed for BIOS systems. It started as Intel's EFI in versions 1.x and then a group of companies called the UEFI Forum took over its development from which it was called Unified EFI starting with version 2.0. As of 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.}}
+
  
== BIOS ==
+
== 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.
 +
* As of 15 April 2015, UEFI Specification 2.5 is the most recent version.
 +
* 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]].
  
A BIOS or Basic Input-Output System is the very first program (firmware) that is executed once the system is switched on. In most cases it is stored in a flash memory in the motherboard itself and independent of the system storage. BIOS launches the first 440 bytes ([[Master Boot Record]]) of the first disk in the BIOS disk order. Since very little can be achieved by a program that fits into the 440-byte boot code area, usually a common boot loader like [[GRUB]] or [[Syslinux]] or [[LILO]] would be loaded by the BIOS, and it would load an operating system by either chain-loading or directly loading the kernel. See [[Arch Boot Process]] for more details.
+
== UEFI Firmware bitness ==
  
== UEFI ==
+
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.
  
UEFI has support for reading both the partition table as well as understanding filesystems. Hence it is not limited by 440 byte code limitation (MBR boot code) as in BIOS systems. It does not use the MBR boot code at all.
+
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.
 
+
The commonly used UEFI firmwares support both MBR and GPT partition table. EFI in Apple-Intel Macs are known to also support Apple Partition Map besides MBR and GPT. Most UEFI firmwares have support for accessing FAT12 (floppy disks), FAT16 and FAT32 filesystems in HDDs and ISO9660 (and UDF) in CD/DVDs. EFI in Intel Macs can also access HFS/HFS+ filesystems, in addition to the mentioned ones.
+
 
+
UEFI does not launch any boot code in the MBR whether it exists or not. Instead it uses a special partition in the partition table called '''EFI System Partition''' in which files required to be launched by the firmware are stored. Each vendor can store its files under {{ic|<EFI SYSTEM PARTITION>/EFI/<VENDOR NAME>/}} folder and can use the firmware or its shell (UEFI shell) to launch the boot program. An EFI System Partition is usually formatted as FAT32 or (less commonly) FAT16.
+
 
+
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 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.
 
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.
  
=== Boot Process under UEFI ===
+
=== Non Macs ===
 
+
# System switched on - Power On Self Test, or POST process.
+
# 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)}}
+
 
+
=== Multibooting in UEFI ===
+
 
+
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.
+
 
+
==== Booting Microsoft Windows ====
+
 
+
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 [[#Using GRUB]] for more info.}}
  
==== 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.  
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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 110: Line 82:
 
=== UEFI Variables Support in Linux Kernel ===
 
=== UEFI Variables Support in Linux Kernel ===
  
Linux kernel exposes EFI variables data to userspace via 2 interfaces:
+
Linux kernel exposes EFI variables data to userspace via '''efivarfs''' ('''EFI''' '''VAR'''iable '''F'''ile'''S'''ystem) interface (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.
  
* '''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'''.
+
=== Requirements for UEFI variable support ===
  
* '''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 .
+
# 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 [[#UEFI Firmware bitness|bitness]] and EFI processor bitness should match
==== Inconsistency between efivarfs and sysfs-efivars ====
+
# 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)
 
+
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
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# mount -t efivarfs efivarfs /sys/firmware/efi/efivars
+
 
+
To disable efivarfs and refresh sysfs-efivars:
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# umount /sys/firmware/efi/efivars
+
# modprobe -r efivarfs
+
+
# modprobe -r efivars
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# modprobe efivars
+
 
+
=== Requirements for UEFI Variables support to work properly ===
+
 
+
# EFI Runtime Services support should be present in the kernel ({{ic|1=CONFIG_EFI=y}})
+
# Kernel processor bitness/arch and EFI processor bitness/arch 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 in the kernel SHOULD NOT be disabled via kernel cmdline, i.e. {{ic|noefi}} kernel parameter SHOULD NOT be used
 
# 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 158: Line 102:
 
==== 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.:
+
{{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] 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}}
+
# '''efivar''' - Library and Tool to manipulate UEFI Variables (used by efibootmgr) - https://github.com/vathpela/efivar - {{Pkg|efivar}} or {{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
+
# '''efibootmgr''' - Tool to manipulate UEFI Firmware Boot Manager Settings - https://github.com/vathpela/efibootmgr - {{Pkg|efibootmgr}} or {{AUR|efibootmgr-git}}
 
# '''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}}  
 
# '''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}}  
 
# '''efitools''' - Tools to Create and Setup own UEFI Secure Boot Certificates, Keys and Signed Binaries (requires efivarfs) - {{AUR|efitools-git}}
 
# '''efitools''' - Tools to Create and Setup own UEFI Secure Boot Certificates, Keys and Signed Binaries (requires efivarfs) - {{AUR|efitools-git}}
# '''Ubuntu's Firmware Test Suite''' - https://wiki.ubuntu.com/FirmwareTestSuite/ - {{AUR|fwts}} (along with {{AUR|fwts-efi-runtime-dkms}}) or {{AUR|fwts-git}}
+
# '''Ubuntu's Firmware Test Suite''' - https://wiki.ubuntu.com/FirmwareTestSuite/ - {{AUR|fwts}}{{Broken package link|{{aur-mirror|fwts}}}} (along with {{AUR|fwts-efi-runtime-dkms}}{{Broken package link|{{aur-mirror|fwts-efi-runtime-dkms}}}}) or {{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 {{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 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 stub location. (for example {{ic|\EFI\refind\refind_x64.efi}}).
 
* The below commands use {{Pkg|refind-efi}} boot-loader as example.
 
* The below commands use {{Pkg|refind-efi}} boot-loader as example.
* Upstream efibootmgr http://linux.dell.com/git/efibootmgr.git does not support efivarfs. However vathpela's efibootmgr supports efivarfs and is currently used in official efibootmgr pkg. sysfs-efivars is also completely disabled in official Arch kernel and it supports only efivarfs. This section is written with the assumtion that you are using only efivarfs and vathpela's efibootmgr.
 
 
}}
 
}}
  
Line 203: Line 150:
 
  # efivar -l
 
  # efivar -l
  
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.
+
If efivar lists the uefi variables without any error, then you can proceed. If not, check whether all the conditions in [[#Requirements for UEFI variable support]] are met.
  
 
Then create the boot entry using efibootmgr as follows:
 
Then create the boot entry using efibootmgr as follows:
Line 216: Line 163:
  
 
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).
 
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 ===
 
 
* 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.}}
 
 
=== MBR partitioned disks ===
 
 
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>}}
 
  
 
== 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), modifyiang 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
* [[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
+
* There are copies of Shell v1 and Shell v2 in the EFI directory on the Arch install media image.
* [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://github.com/tianocore/edk2/tree/master/ShellBinPkg Precompiled UEFI Shell v2 binaries] (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://github.com/tianocore/edk2/tree/master/EdkShellBinPkg Precompiled UEFI Shell v1 binaries] (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]
 
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]
Line 266: Line 188:
 
=== 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 272: Line 194:
 
==== 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 "UEFI Shell Specification 2.0" PDF 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. 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.
 
}}
 
}}
Line 288: Line 210:
  
 
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
 +
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 304: Line 233:
  
 
  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> fs0:
Line 319: Line 257:
 
== 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 325: Line 263:
 
=== Create UEFI bootable USB from ISO ===
 
=== Create UEFI bootable USB from ISO ===
  
{{Note|1=The instructions below are specifically for [[Archiso]]/official media; [[Archboot]] preparation is identical, without the filesystem label requirement.}}
+
Follow [[USB flash installation media#BIOS and UEFI Bootable USB]]
  
==== In Linux ====
+
=== Remove UEFI boot support from Optical Media ===
  
* [[Beginners_Guide#Prepare_the_storage_drive|First create either a MBR or GPT (recommended) partition table and at least one partition in the USB]] (so it is fine to use an already partitioned USB). {{Note|Using a GPT partition table is recommended as some firmwares do not support booting from MBR devices in full UEFI mode (e.g. Gigabyte).}}
+
{{Note|This section mentions removing UEFI boot support from a '''CD/DVD only''' (Optical Media), not from a USB flash drive.}}
 
+
* Mount the ISO image from the [https://www.archlinux.org/download/ Arch Linux download page].
+
 
+
# mkdir -p /mnt/{usb,iso}
+
# mount -o loop archlinux-2013.10.01-dual.iso /mnt/iso
+
 
+
* Then create a FAT32 filesystem in the partition on the USB (unmount before if necessary) with LABEL as used in the Archiso configuration. Obtain the label from {{ic|/mnt/iso/loader/entries/archiso-x86_64.conf}}; this is used by the {{ic|archiso}} hook in initramfs to identify the udev path to the installation media. {{ic|mkfs.fat}} is part of package {{Pkg|dosfstools}}. {{Note|The filesystem should be either FAT32 (recommended), FAT16, or FAT12.}}
+
 
+
# awk 'BEGIN {FS="="} /archisolabel/ {print $3}' /mnt/iso/loader/entries/archiso-x86_64.conf | xargs mkfs.fat -F32 /dev/sdXY -n
+
 
+
* Mount the newly created FAT32 USB partition, and copy the contents of the installation media to the USB media.
+
 
+
# mount /dev/sdXY /mnt/usb
+
# cp -a /mnt/iso/* /mnt/usb
+
# sync
+
# umount /mnt/{usb,iso}
+
 
+
==== In Windows ====
+
 
+
{{Note|Do not use any '''Bootable USB Creator utility''' for creating the UEFI bootable USB. Do not use ''dd for Windows'' to dd the ISO to the USB drive.}}
+
 
+
* Format the USB drive as FAT32. {{Note|The filesystem should be either FAT32 (recommended), FAT16, or FAT12.}}
+
 
+
* Extracted the ISO (similar to extracting ZIP archive) to the USB drive using [http://7-zip.org/ 7-Zip].
+
 
+
* Change the '''Volume Label''' of the USB drive to match the LABEL mentioned in {{ic|1=archisolabel=}} part in {{ic|<USB>\loader\entries\archiso-x86_64.conf}} . {{Note|The above step is required for Official ISO (archiso) but not required for [[Archboot]].}}
+
 
+
=== Remove UEFI boot support from ISO ===
+
 
+
{{Warning|In the event that UEFI+isohybrid El Torito/MBR really causes problems, it would be better to just UEFI boot using the USB stick instructions in the previous section}}
+
  
 
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.
 
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 {{ic|archisolabel}} as shown in the previous section.
+
* Mount the official installation media and obtain the {{ic|archisolabel}} as shown in the previous section.
  
Rebuild the ISO using {{ic|xorriso}} from {{pkg|libisoburn}}:
+
# mount -o loop ''input.iso'' /mnt/iso
  
{{bc|<nowiki>
+
* 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=
 
$ xorriso -as mkisofs -iso-level 3 \
 
$ xorriso -as mkisofs -iso-level 3 \
 
     -full-iso9660-filenames\
 
     -full-iso9660-filenames\
     -volid "ARCH_201212" \
+
     -volid "''archisolabel''" \
 
     -appid "Arch Linux CD" \
 
     -appid "Arch Linux CD" \
 
     -publisher "Arch Linux <https://www.archlinux.org>" \
 
     -publisher "Arch Linux <https://www.archlinux.org>" \
     -preparer "prepared like a BAWSE" \
+
     -preparer "prepared by $USER" \
 
     -eltorito-boot isolinux/isolinux.bin \
 
     -eltorito-boot isolinux/isolinux.bin \
 
     -eltorito-catalog isolinux/boot.cat \
 
     -eltorito-catalog isolinux/boot.cat \
 
     -no-emul-boot -boot-load-size 4 -boot-info-table \
 
     -no-emul-boot -boot-load-size 4 -boot-info-table \
 
     -isohybrid-mbr "/mnt/iso/isolinux/isohdpfx.bin" \
 
     -isohybrid-mbr "/mnt/iso/isolinux/isohdpfx.bin" \
     -output "~/archiso.iso" "/mnt/iso/"
+
     -output ''output.iso'' /mnt/iso/
</nowiki>}}
+
}}
  
Burn {{ic|~/archiso.iso}} to optical media and proceed with installation normally.
+
* Burn {{ic|''output.iso''}} to optical media and proceed with installation normally.
  
 
== Testing UEFI in systems without native support ==
 
== Testing UEFI in systems without native support ==
Line 387: Line 296:
 
=== 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 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 and run it as follows:
  
  $ qemu-system-x86_64 -enable-kvm -net none -m 1024 -bios /usr/share/ovmf/x86_64/bios.bin  
+
  $ qemu-system-x86_64 -enable-kvm -net none -m 1024 -drive file=/usr/share/ovmf/ovmf_x64.bin,format=raw,if=pflash,readonly
  
 
=== DUET for BIOS only systems ===
 
=== DUET for BIOS only systems ===
Line 403: Line 312:
 
=== 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.
  
- UEFI BIOS option for booting UEFI Only does not pretend the UEFI BIOS from starting CSM
+
=== Windows changes boot order ===
 +
In some motherboards (confirmed in ASRock Z77 Extreme4) Windows 8 changes the boot order in the NVRAM everytime is booted. This can be fixed making the Windows Boot Manager to load another loader instead of booting Windows.
 +
Run this command in a Administrator mode console in Windows:
 +
bcdedit /set {bootmgr} path \EFI\boot_app_dir\boot_app.efi
 +
 
 +
=== 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.
 +
 
 +
* If the issue is not due to KMS, then it may be due to bug in [[EFISTUB]] booting (see {{Bug|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.
 +
 
 +
==== Using GRUB ====
 +
{{Deletion|Through bug report this issue should be fixed in kernel 3.16 and after, so this workaround is not needed anymore.}}
 +
{{Tip|The given configuration entries can also be entered inside a [[GRUB#Using_the_command_shell|GRUB command-shell]].}}
 +
 
 +
* [[USB flash installation media#BIOS_and_UEFI_Bootable_USB|Create an USB Flash Installation]]
 +
 
 +
* Backup {{ic|EFI/boot/loader.efi}} to {{ic|EFI/boot/gummiboot.efi}}
 +
 
 +
* [[GRUB#GRUB_standalone|Create a GRUB standalone image]] and copy the generate {{ic|grub*.efi}} to the USB as {{ic|EFI/boot/loader.efi}}, {{ic|EFI/boot/bootx64.efi}} and/or {{ic|EFI/boot/bootia32.efi}} (useful when running on a 32-bit UEFI)
 +
 
 +
* 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>
 +
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
 +
}
 +
</nowiki>}}
 +
 
 +
{{hc|grub.cfg for Archboot ISO|<nowiki>
 +
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
 +
}
 +
</nowiki>}}
 +
 
 +
=== UEFI boot loader does not show up in firmware menu ===
 +
 
 +
On some UEFI motherboards like 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://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://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]
 
 
* [http://www.intel.com/technology/efi/ Intel's page on EFI]
 
* [http://www.intel.com/technology/efi/ Intel's page on EFI]
 +
* [http://uefidk.intel.com/ Intel UEFI Community Resource Center]
 +
* [http://uefidk.intel.com/blog/linux-efi-boot-stub Matt Fleming - The Linux EFI Boot Stub]
 +
* [http://uefidk.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://homepage.ntlworld.com/jonathan.deboynepollard/FGA/efi-boot-process.html FGA: The EFI boot process]
 
* [http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/efi-boot-process.html FGA: The EFI boot process]
* [http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx Microsoft's Windows and GPT FAQ] - Contains info on Windows UEFI booting also
+
* [http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx Microsoft's Windows and GPT FAQ]
* [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/Windows_x64_BIOS_to_UEFI Convert Windows x64 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]
 
* [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://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 12:07, 30 April 2016

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 mainboard 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.
  • As of 15 April 2015, UEFI Specification 2.5 is the most recent version.
  • 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.

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 #Using GRUB for more info.

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. EFI Runtime Services support should be present in the kernel (CONFIG_EFI=y, check if present with zgrep CONFIG_EFI /proc/config.gz).
  2. Kernel processor bitness and EFI processor bitness should match
  3. 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)
  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

Warning: efivars is mounted writeable by default [1], which may cause permanent damage to the system. [2] 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

  1. efivar - Library and Tool to manipulate UEFI Variables (used by efibootmgr) - https://github.com/vathpela/efivar - efivar or efivar-gitAUR
  2. efibootmgr - Tool to manipulate UEFI Firmware Boot Manager Settings - https://github.com/vathpela/efibootmgr - efibootmgr or efibootmgr-gitAUR
  3. 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 uefivars-gitAUR
  4. efitools - Tools to Create and Setup own UEFI Secure Boot Certificates, Keys and Signed Binaries (requires efivarfs) - efitools-gitAUR
  5. Ubuntu's Firmware Test Suite - https://wiki.ubuntu.com/FirmwareTestSuite/ - fwtsAUR[broken link: archived in aur-mirror] (along with fwts-efi-runtime-dkmsAUR[broken link: archived in aur-mirror]) or fwts-gitAUR

efibootmgr

Note:
  • If efibootmgr completely fails to work in your system, you can reboot into UEFI Shell v2 and use bcfg command 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 stub location. (for example \EFI\refind\refind_x64.efi).
  • The below commands use refind-efi boot-loader as example.

Assuming the boot-loader file to be launched is /boot/efi/EFI/refind/refind_x64.efi, /boot/efi/EFI/refind/refind_x64.efi can be split up as /boot/efi and /EFI/refind/refind_x64.efi, wherein /boot/efi is the mountpoint of the EFI System Partition, which is assumed to be /dev/sdXY (here X and Y are just placeholders for the actual values - eg:- in /dev/sda1 , X==a Y==1).

To determine the actual device path for the EFI System Partition (assuming mountpoint /boot/efi for example) (should be in the form /dev/sdXY), try :

# findmnt /boot/efi
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:

# efivar -l

If efivar lists the uefi variables without any error, then you can proceed. If not, check whether all the conditions in #Requirements for UEFI variable support 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: UEFI uses backward slash \ as path separator (similar to Windows paths), but the official efibootmgr pkg support passing unix-style paths with forward-slash / as path-separator for the -l option. Efibootmgr internally converts / to \ 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 /boot/efi/EFI/refind/refind_x64.efi translates to /boot/efi and /EFI/refind/refind_x64.efi which in turn translate to drive /dev/sdX -> partition Y -> file /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 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 \EFI\refind\refindx64.efi or \efi\refind\refind_x64.efi does not matter (this will change if the filesystem encoding is UTF-8).

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

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 "UEFI Shell Specification 2.0" PDF 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. You can download 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
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> fs0:
FS0:\> cd \EFI\arch\refind
FS0:\EFI\arch\refind\> edit 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 for QEMU.

You can install ovmf from the extra repository and run it as follows:

$ qemu-system-x86_64 -enable-kvm -net none -m 1024 -drive file=/usr/share/ovmf/ovmf_x64.bin,format=raw,if=pflash,readonly

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.

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

In some motherboards (confirmed in ASRock Z77 Extreme4) Windows 8 changes the boot order in the NVRAM everytime is booted. This can be fixed making the Windows Boot Manager to load another loader instead of booting Windows. Run this command in a Administrator mode console in Windows:

bcdedit /set {bootmgr} path \EFI\boot_app_dir\boot_app.efi

USB media gets struck with black screen

  • This issue can occur either due to KMS issue. Try 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 FS#33745 and [3] 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.

Using GRUB

Tango-edit-cut.pngThis section is being considered for removal.Tango-edit-cut.png

Reason: Through bug report this issue should be fixed in kernel 3.16 and after, so this workaround is not needed anymore. (Discuss in Talk:Unified Extensible Firmware Interface#)
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 a GRUB standalone image and copy the generate grub*.efi to the USB as EFI/boot/loader.efi, EFI/boot/bootx64.efi and/or EFI/boot/bootia32.efi (useful when running on a 32-bit UEFI)
  • 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 some UEFI motherboards like 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