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UKI

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Reference:wiki.archlinux.org

Boot kernel directly from UEFI ​

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With this setup there is no need to use grub.

Configure the kernel command line in /etc/kernel/cmdline. Example:

shell
root=UUID=1a3448da-b6df-400b-b85e-695cca6eeba1 rw loglevel=3 quiet splash cryptdevice=/dev/disk/by-label/swap:encSwap cryptkey=/dev/disk/by-label/USB_LOADER:vfat:/swap_keyfile resume=/dev/mapper/encSwap

Next modify /etc/mkinitcpio.d/linux.preset as follows:

  • Un-comment the PRESET_uki= parameter for each item in PRESETS=,
  • Optionally, comment out PRESET_image= to avoid storing a redundant initramfs-*.img file,
  • Optionally, add or un-comment the --splash parameter to each PRESET_options= line for which you want to add a splash image.

Example:

shell
# mkinitcpio preset file for the 'linux' package

#ALL_config="/etc/mkinitcpio.conf"
ALL_kver="/boot/vmlinuz-linux"

PRESETS=('default' 'fallback')

#default_config="/etc/mkinitcpio.conf"
#default_image="/boot/initramfs-linux.img"
default_uki="/efi/EFI/Linux/arch-linux.efi"
default_options="--splash /usr/share/systemd/bootctl/splash-arch.bmp"

#fallback_config="/etc/mkinitcpio.conf"
#fallback_image="/boot/initramfs-linux-fallback.img"
fallback_uki="/efi/EFI/Linux/arch-linux-fallback.efi"
fallback_options="-S autodetect"

Build the UKIs into /efi/EFI/Linux:

shell
mkdir -p /efi/EFI/Linux
mkinitcpio -p linux

Note: Make sure to have enough space in the efi partition.

txt
> du -ha /efi
52M	/efi/EFI/Linux/arch-linux.efi
125M	/efi/EFI/Linux/arch-linux-fallback.efi
176M	/efi/EFI/Linux
177M	/efi/EFI
4.0K	/efi/loader/random-seed
8.0K	/efi/loader
177M	/efi

Finally we can boot directly from UEFI using efibootmgr:

shell
efibootmgr --create --disk /dev/nvme0n1 --part 1 --label 'Arch Linux' --loader '\EFI\Linux\arch-linux.efi' --unicode