Unified Extensible Firmware Interface (简体中文) - ArchWiki

# Unified Extensible Firmware Interface (简体中文)

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统一可扩展固件界面（Unified Extensible Firmware Interface） (或简称为UEFI) 是一种新型固件，最初是由Intel设计(当时称为EFI)，主要用于其基于安腾架构的系统。 它介绍了一种新的启动系统的方式，该方式有别于传统BIOS系统所使用的“MBR启动代码”。它起始于Intel EFI的1.x版本，之后被称作UEFI论坛的一群公司接管了它的开发工作。从此，它被称为统一的EFI，其版本始于2.0。自2013年7月24号起，UEFI规格2.4（在2013年7月11日发布）是最新的一个版本。

Note:

- 这篇只说明了 什么是UEFI 跟 UEFI在Linux内核中的支持。并没有详细解释UEFI启动器的设置。如果需要请看Boot loaders。
- 除非特别指定为EFI 1.x，否者EFI以及UEFI这两者是可以互换使用的，均是指UEFI 2.x固件。同样，除非明确指出，以下的说明是通用的，不过有些可能在 Mac 系统上不工作或者不一样。苹果的 EFI 实现既不是EFI 1.x 也不是 UEFI 2.x 而是一种混合。这类固件不归于任何一个 UEFI 版本，因此也不是标准的 UEFI 固件。

## BIOS和UEFI的不同

参考 Arch boot process (简体中文)#固件种类 。

## UEFI 引导过程

1. 系统开机 - 上电自检（Power On Self Test 或 POST）。
2. UEFI 固件被加载。固件初始化启动要用的硬件。
3. 固件读取其引导管理器以确定从何处（比如，从哪个硬盘及分区）加载哪个 UEFI 应用。
4. 固件按照引导管理器中的启动项目，加载UEFI 应用。
5. 已启动的 UEFI 应用还可以启动其他应用（对应于 UEFI shell 或 rEFInd 之类的引导管理器的情况）或者启动内核及initramfs（对应于GRUB之类引导器的情况），这取决于 UEFI 应用的配置。

Note: 在有些 UEFI 系统中，唯一可行的启动时（如果应用没有在 UEFI 启动菜单定制条目的话）加载 UEFI 应用的方法是把它放在此固定位置：`<EFI SYSTEM PARTITION>/EFI/boot/bootx64.efi` （对于 64 位的 x86 系统）

### UEFI 的多重引导

因为每个操作系统或者提供者都可以维护自己的 EFI 系统分区中的文件，同时不影响别人，所以 UEFI 的多重启动只是简单的运行不同的UEFI 程序，对应于特定操作系统的引导程序。这避免了依赖 chainloading 机制（通过一个引导程序加载另一个引导程序，来切换操作系统）。

#### 启动 Microsoft Windows

##### Linux Windows x86_64 UEFI-GPT Multiboot

64位版本的 Windows Vista (SP1+)、Windows 7 和 Windows 8 源生支持通过 UEFI 固件引导，但是这需要将硬盘格式化为 GPT 格式。64位版本的 Windows 系统支持 UEFI-GPT 模式引导或 BIOS-MBR 模式引导，而32位版本的 Windows 系统仅支持 BIOS-MBR 模式引导。具体做法请参考论坛参考文献章节中提供的链接。查看 http://support.microsoft.com/default.aspx?scid=kb;EN-US;2581408 来获得更多信息。

这种限制在 Linux 内核中并不存在，而是取决于所使用的引导程序。如果在同一块硬盘中引导 Linux 和 Windows，为了使 Windows 能使用 UEFI 引导，Linux 引导程序也必须使用 UEFI-GPT 模式安装。

### 检测 UEFI 固件架构版本

#### 非 Macs

检查目录 `/sys/firmware/efi` 是否存在，如果存在表明内核已经以 UEFI 模式启动，这种情况下 UEFI 版本等同于内核版本。(例如： i686 或者 x86_64)

#### Macs

2008年以前的 Macs 大都使用 i386-efi 固件， 2008年以后大都使用 x86_64-efi 。有能力运行 Mac OS X Snow Leopard 64-bit 内核的 Macs 都是 x86_64 EFI 1.x 版的固件。

在 Mac OS 下输入以下命令可以找出该 Mac 的 efi 固件：

    ioreg -l -p IODeviceTree | grep firmware-abi

如果命令返回 EFI32 则对应的是 i386 EFI 1.x 版本的固件，返回 EFI64 对应的则是 x86_64 EFI 1.x 版的固件. Macs 没有 UEFI 2.x 固件，Apple's EFI 的实现也不完全跟 UEFI 标准兼容。

### 安全启动

关于在 Linux 中的安全启动的概述请参考 http://www.rodsbooks.com/efi-bootloaders/secureboot.html。 本节的重点在于如何在 Arch Linux 中设置安全启动。本节暂时仅介绍在开启安全启动模式的情况下启动 archiso 的步骤。因为 efi 程序 PreLoader.efi 和 HashTool.efi 已经添加到 archiso 中，所以在开启安全启动模式的情况下启动 archiso 是可以的。一条 Failed to Start loader...I will now execute HashTool. 的消息将会显示。要使用 HashTool 来注册 loader.efi 和 vmlinuz.efi 的 hash 值，执行如下步骤：

- 选择 `OK`
- 在 HashTool 主菜单先选择 `Enroll Hash`，再选择 `\loader.efi`，然后点击 `Yes` 确认。再选择 `Enroll Hash` 和 `archiso`，进入 archiso 目录，然后选择 `vmlinuz-efi` 并且点击 `Yes` 确认，最后点击 `Exit` 返回启动设备选择菜单。
- 在启动设备选择菜单选择 `Arch Linux archiso x86_64 UEFI CD`。

archiso 启动后会自动以 root 登陆，并且出现 shell 提示符。使用以下命令检查 archiso 是否以安全启动模式启动：

    $ od -An -t u1 /sys/firmware/efi/efivars/SecureBoot-XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX

如果以安全启动模式启动，命令会返回以 1 结尾的五个整数，例如：

    6  0  0  0  1

XXXX 部分因不同机器而各不相同。可以使用 tab 补全来获取帮助或者列出 efi 变量。

## Linux 内核中有关 UEFI 的配置选项

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 变量

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

### Linux内核中的UEFI变量支持

Linux kernel exposes EFI variables data to userspace via 2 interfaces:

- OLD sysfs-efivars interface (CONFIG_EFI_VARS) - populated by `efivars` kernel module at `/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.

- NEW efivarfs (EFI VARiable FileSystem) interface (CONFIG_EFIVAR_FS) - mounted using `efivarfs` kernel module at `/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 `efivarfs` module split from OLD `efivars` kernel module in kernel 3.10 .

#### efivarfs 和 sysfs-efivars 的不一致

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/linux-3.11 and core/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, `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

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/arch and EFI processor bitness/arch 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. For sample output see #Sample_List_of_UEFI_Variables.

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.

#### 挂载 efivarfs

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

如果启动时 systemd 没有自动挂载 `efivarfs` 到 `/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.

It is also a good idea to auto-mount `efivarfs` during boot via `/etc/fstab` as follows:

也可以在启动时通过 `/etc/fstab` 自动挂载 `efivarfs`，在 `/etc/fstab` 添加以下行：

    /etc/fstab

    efivarfs    /sys/firmware/efi/efivars    efivarfs    defaults    0    0

### 用户空间工具

有几个访问和编辑 UEFI 变量的工具如下：

1. efibootmgr - 用于创建/编辑 UEFI 引导管理器中的引导项 - 见efibootmgr 或 efibootmgr-git
2. uefivars - 转储 UEFI 变量 - 见uefivars-git - 需用到 efibootmgr 库
3. Ubuntu的固件测试套件（fwts）- 见fwts-git - uefidump 命令 - `fwts uefidump`

##### efibootmgr

Warning:

This article or section is being considered for deletion.

Reason: Since the bug is fixed, there is nothing to warn about. (Discuss)

- Using `efibootmgr` on Apple Macs with old kernels may brick the firmware and may need reflash of the motherboard ROM. There have been bug reports regarding this in Ubuntu/Launchpad bug tracker.

The bug is reported to be fixed (see [[1]])

- Use the Mac OS bless command in case you are unsure. Experimental "bless" utility for Linux by Fedora developers - mactel-boot.

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 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: 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).

## EFI 系统分区

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 link.

EFI 系统分区（也称为 ESP 或者 EFISYS）是一个 FAT32 格式的物理分区（

Note:

- It is recommended to use always GPT for UEFI boot as some UEFI firmwares do not allow UEFI-MBR boot.
- In GNU Parted, `boot` flag (not to be confused with `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 `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 = 256 MB. Advanced Format 512e drives are not affected by this limitation, because their emulated sector size is 512 bytes. 512 bytes x 65527 = 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 `/boot` partition itself instead of a separate `/boot` partition, for EFISTUB booting.

### GPT 磁盘分区

- Create a partition with partition type `ef00` or `EF00` using gdisk (from gptfdisk pkg). Then format that partition as FAT32 using `mkfs.fat -F32 /dev/<THAT_PARTITION>`

(or)

- Create a FAT32 partition and in GNU Parted set/activate the `boot` flag (not `legacy_boot` flag) on that partition

- 使用 gdisk （从 gptfdisk 包中获取）创建一个分区，分区类型设置为 `ef00` 或者 `EF00`。然后使用 `mkfs.fat -F32 /dev/<THAT_PARTITION>` 命令将分区格式化为 FAT32 格式。

或者

- 创建一个 FAT32 分区，使用 GNU 分区工具设置/激活该分区的 `boot` 标志（不是 `legacy_boot` 标志）。

Note: If you get the message `WARNING: Not enough clusters for a 32 bit FAT!`, reduce cluster size with `mkfs.fat -s2 -F32 ...` or `-s1`, otherwise the partition may be unreadable by UEFI.

### MBR partitioned disks

Create a partition with partition type `0xEF` using fdisk (from util-linux pkg). Then format that partition as FAT32 using `mkfs.fat -F32 /dev/<THAT_PARTITION>`

### ESP on RAID

It is possible to make the ESP part of a RAID1 array, but doing so brings the risk of data corruption, and further considerations need to be taken when creating the ESP. See https://bbs.archlinux.org/viewtopic.php?pid=1398710#p1398710 and https://bbs.archlinux.org/viewtopic.php?pid=1390741#p1390741 for details.

## 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.

- 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
- Precompiled x86_64 UEFI Shell v2 binary (may not be up-to-date)
- Precompiled x86_64 UEFI Shell v1 binary (not updated anymore upstream)
- Precompiled IA32 UEFI Shell v2 binary (may not be up-to-date)
- 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 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. `map` lists recognized filesystems (`fs0`, ...) and data storage devices (`blk0`, ...). Run `help -b` to list available commands.

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

#### 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.

Note:

- Users are recommended to try `bcfg` only if `efibootmgr` fails to create working boot entries in their 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 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

#### 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.

To edit, for example 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

Main page HCL/Firmwares/UEFI

## UEFI Bootable Media

### 从 ISO 文件创建一个支持 UEFI 的启动盘

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/

## 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 build OVMF (with Secure Boot support) from AUR ovmf-svn and run it as follows:

    $ qemu-system-x86_64 -enable-kvm -net none -m 1024 -pflash /usr/share/ovmf/x86_64/bios.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://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 [2] 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

- Create USB Flash Installation drive as mentioned in link. After that follow the below steps to use GRUB instead of Gummiboot.

- Backup `<USB>/EFI/boot/loader.efi` to `<USB>/EFI/boot/gummiboot.efi`

- Create a GRUB standalone image and copy it to `<USB>/EFI/boot/loader.efi`

- Create `<USB>/EFI/boot/grub.cfg` with the following contents (replace `ARCH_YYYYMM` with the label of the USB disk e.g. `ARCH_201404`):

    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
    }

## See also

- Wikipedia's page on UEFI
- Wikipedia's page on UEFI SYSTEM Partition
- Linux Kernel UEFI Documentation
- UEFI Forum - contains the official UEFI Specifications - GUID Partition Table is part of UEFI Specification
- Intel's Tianocore Project for Open-Source UEFI firmware which includes DuetPkg for direct BIOS based booting and OvmfPkg used in QEMU and Oracle VirtualBox
- Intel's page on EFI
- FGA: The EFI boot process
- Microsoft's Windows and GPT FAQ - Contains info on Windows UEFI booting also
- Convert Windows Vista SP1+ or 7 x86_64 boot from BIOS-MBR mode to UEFI-GPT mode without Reinstall
- Create a Linux BIOS+UEFI and Windows x64 BIOS+UEFI bootable USB drive
- Rod Smith - A BIOS to UEFI Transformation
- UEFI Boot problems on some newer machines (LKML)
- EFI Shells and Scripting - Intel Documentation
- UEFI Shell - Intel Documentation
- UEFI Shell - bcfg command info
- Some useful 32-bit UEFI Shell utilities
- LPC 2012 Plumbing UEFI into Linux
- LPC 2012 UEFI Tutorial : part 1
- LPC 2012 UEFI Tutorial : part 2

Category:

- Boot process (简体中文)