ユニファイドカーネルイメージ

Unified カーネルイメージ は単一の実行ファイルで、UEFI ファームウェアから直接起動したり、ブートローダによってほとんどあるいは全く設定なしで自動的に起動することができます。

Arch がサポートするカーネル自体は can be loaded by UEFI firmware ですが、ユニファイドイメージはそれを組み込むことを可能にします。

• systemd-stub(7) のような UEFI スタブローダー。
• kernel イメージです。
• initramfs イメージ
• カーネルコマンドライン
• オプションでスプラッシュスクリーンを表示します。

出来上がった実行ファイル、つまりこれら全ての要素は、signed で簡単にセキュアブート で使用できるようにすることができます。

ノート: 記事全体で esp は EFI システムパーティション のマウントポイントを表します。

Preparing a unified kernel image

mkinitpcio

One can test the feature by running as an example

# mkinitcpio -p linux -- --uefi esp/EFI/Linux/test-systemd.efi

This would produce a kernel image for the linux preset.

.preset file

First, modify /etc/mkinitcpio.d/linux.preset, or the preset that you are using, as follows, with the appropriate mount point of the EFI system partition :

• If your system requires Microcode, add ALL_microcode=(/boot/*-ucode.img) to tell mkinitcpio where to find it.
• Add a PRESET_efi_image= parameter for each item in PRESETS=, i.e. default_efi_image="esp/EFI/Linux/archlinux-linux.efi" and fallback_efi_image="esp/EFI/Linux/archlinux-linux-fallback.efi". This sets the executable filename.
• Optionally, append --splash /usr/share/systemd/bootctl/splash-arch.bmp to each PRESET_options= line to add a splash image, i.e. default_options="--splash /usr/share/systemd/bootctl/splash-arch.bmp" and fallback_options="-S autodetect --splash /usr/share/systemd/bootctl/splash-arch.bmp".

Here is a working example linux.preset for the linux kernel and the Arch splash screen.

/etc/mkinitcpio.d/linux.preset

# mkinitcpio preset file for the 'linux' package

ALL_config="/etc/mkinitcpio.conf"
ALL_kver="/boot/vmlinuz-linux"
ALL_microcode=(/boot/*-ucode.img)

PRESETS=('default' 'fallback')

default_image="/boot/initramfs-linux.img"
default_efi_image="esp/EFI/Linux/archlinux-linux.efi"
default_options="--splash /usr/share/systemd/bootctl/splash-arch.bmp"

fallback_image="/boot/initramfs-linux-fallback.img"
fallback_efi_image="esp/EFI/Linux/archlinux-linux-fallback.efi"
fallback_options="-S autodetect --splash /usr/share/systemd/bootctl/splash-arch.bmp"

This second example builds a default image for linux and a fallback image for linux-lts :

/etc/mkinitcpio.d/linux.preset

ALL_config="/etc/mkinitcpio.conf"
ALL_microcode=(/boot/*-ucode.img)

PRESETS=('default' 'fallback')

default_kver="/boot/vmlinuz-linux"
default_image="/boot/initramfs-linux.img"
default_efi_image="/boot/EFI/Linux/archlinux-linux.efi"
default_options="--splash /usr/share/systemd/bootctl/splash-arch.bmp"

fallback_kver="/boot/vmlinuz-linux-lts"
fallback_image="/boot/initramfs-linux-lts-fallback.img"
fallback_efi_image="/boot/EFI/Linux/archlinux-linux-lts-fallback.efi"
fallback_options="-S autodetect --splash /usr/share/systemd/bootctl/splash-arch.bmp"

ヒント: If you are using multiple kernels, make sure your ESP has enough space, as mkinitcpio currently builds both the initramfs-*.img and the *.efi executable, thereby doubling the space used. See [1]

Kernel command line

Next, create /etc/kernel/cmdline with your kernel parameters.

# cp /proc/cmdline /etc/kernel/cmdline

警告: initrd entries pointing at microcode and the initramfs need to be removed.

For example:

/etc/kernel/cmdline

rw quiet bgrt_disable

ヒント: The bgrt_disable parameter tells Linux to not display the OEM logo after loading the ACPI tables.

Finally, regenerate the initramfs.

dracut

Place your command line parameters in ie. /etc/dracut.conf.d/cmdline.conf

Generate the image with:

# dracut -f -q --uefi --uefi-splash-image /usr/share/systemd/bootctl/splash-arch.bmp

Also see dracut#Generate a new initramfs on kernel upgrade.

Manually

Put the kernel command line you want to use in a file, and create the bundle file using objcopy(1).

For microcode, first concatenate the microcode file and your initrd, as follows:

$ cat /boot/cpu_manufacturer-ucode.img /boot/initramfs-linux.img > /tmp/combined_initrd.img

When building the unified kernel image, passing /tmp/combined_initrd.img as the initrd. This file can be afterwards.

$ objcopy \
    --add-section .osrel="/usr/lib/os-release" --change-section-vma .osrel=0x20000 \
    --add-section .cmdline="/etc/kernel/cmdline" --change-section-vma .cmdline=0x30000 \
    --add-section .splash="/usr/share/systemd/bootctl/splash-arch.bmp" --change-section-vma .splash=0x40000 \
    --add-section .linux="vmlinuz-file" --change-section-vma .linux=0x2000000 \
    --add-section .initrd="initrd-file" --change-section-vma .initrd=0x3000000 \
    "/usr/lib/systemd/boot/efi/linuxx64.efi.stub" "linux.efi"

See [2] for an explanation on why these exact numbers were chosen.

After creating the image, copy it to the EFI system partition:

# cp linux.efi esp/EFI/Linux/

Booting

systemd-boot

systemd-boot searches in esp/EFI/Linux/ for unified kernel images, and there is no further configuration needed. See sd-boot(7) § FILES

Directly from UEFI

efibootmgr can be used to create a UEFI boot entry for the .efi file:

# efibootmgr --create --disk /dev/sdX --part partition_number --label "label" --loader 'EFI\Linux\file.efi' --verbose

See efibootmgr(8) for an explanation of the options.

See also

• mkinitcpio v31 and UEFI stubs