U Boot

U-Boot in combination with m1n1 and device trees can be used to load grub or any other efi boot loader from vfat esp partition located on the internal NVMe drive or an USB stick. Grub can than load a Linux kernel and initird to boot Linux. U-Boot will try to load EFI/BOOT/BOOTAA64.EFI. Make sure that grub or any other boot loader is located there.

U-Boot Installation Video

Tripwires

The USB-a ports on the mac mini will not work in u-boot and grub. The two additional USB-3 ports on the iMac 4 port model also don't work.

In order that the internal keyboard work on pro/max models you need the following two kernel patches:

https://tg.st/u/256f5efbf23ff68c489dad92f99d1cecfb021729.patch
https://tg.st/u/8737955a0263d09ffa8550658dfcac1df3d0665c.patch

Prerequisit: Bootchain

In order to use u-boot, you need three extra partitions: The Linux stub from the asahi installer, an vfat EFI System Partition (esp) and a root partion. Optionally a boot partition if you have an encrypted root device. Not covered here.

Under MacOS, lets make space - the last number is the space that macos will occupy. It is recommended to have at least 70 GB. I recommend on leaving at least 100 GB for macos.

diskutil apfs resizeContainer disk0s2 200GB

Than run the Asahi Installer. In the MacOS Boot picker, you have to unlock, select Linux and click on Restart.

curl -L https://mrcn.st/alxsh | sh

Wait for the system to shutdown and the LEDs turn off. Than wait another 5 seconds. Now press and do not let go of the power button for 15 seconds. In the boot picker, select 'Options' and select Utilities > Terminal. In this terminal execute. If you screw the power button holding, turn the System off by pressing the power button until it is off and start from the beginning of this paragraph.

/Volumes/Linux/step2.sh

Create an EFI parition because the final layout will have that

diskutil list
diskutil addPartition <identifier before free space> %EFI% LB 512MB

Create partition to hold a root filesystem

diskutil list
diskutil addPartition <identifier before free space> %Linux% %noformat% <size>

Building

In order to get the boot object, we need to build m1n1 and u-boot and concatenate the two and the device trees from the kernel. m1n1 automatically picks the right device tree for the model you're booting it on.

git clone --depth 1 https://github.com/jannau/u-boot -b x2r10g10b10
cd u-boot
make apple_m1_defconfig
make -j 16

git clone --recursive https://github.com/AsahiLinux/m1n1.git
cd m1n1
make -j
cd ..

cat m1n1/build/m1n1.macho `find linux/arch/arm64/boot/dts/apple/ -name \*.dtb` u-boot/u-boot-nodtb.bin > u-boot.macho
cat m1n1/build/m1n1.bin `find linux/arch/arm64/boot/dts/apple/ -name \*.dtb` u-boot/u-boot-nodtb.bin > u-boot.bin

Binary

FIXME; This should be hosted by marcan or better included in the installer

You can download a prebuild version which was built by Thomas Glanzmann from here:

curl -LO https://tg.st/u/u-boot.macho
curl -LO https://tg.st/u/u-boot.bin

Installing

In order to install the u-boot.macho object, we need to make sure that Linux boots by default, power off the m1 system completely, and boot it by holding the power button until it says 'showing boot options', than select the Options menu. Open a terminal, download u-boot.macho that you build in the previous step and run the following command:

# <= MaOS 12.0.1
kmutil configure-boot -c u-boot.macho -v /Volumes/Linux
# Macos 12.1 and newer
kmutil configure-boot -c u-boot.bin --raw --entry-point 2048 --lowest-virtual-address 0 -v /Volumes/Linux

Arch

Move Image.gz to /boot

grub-mkconfig -o /boot/grub/grub.cfg

Debian

The esp vfat partition should be mounted to /boot/efi. Replace the X with your partition:

lsblk
mkdir -p /boot/efi
echo '/dev/nvme0n1pX /boot/efi vfat defaults 0 0' >> /etc/fstab
mount /boot/efi

Install grub and make sure grub-efi-arm64-signed is not installed because it makes u-boot hang.

apt-get install grub-efi grub-efi-arm64-signed-

Install grub where u-boot expects it by specifying the --removable flag

grub-install --target=arm64-efi --efi-directory=/boot/efi --removable

Also run the following command and set Force extra installation to the EFI removable media path to yes and update nvrma to no in order to make grub updates not break your bootchain.

dpkg-reconfigure grub-efi-arm64

Do not forget to update-grub afterwards:

update-grub

Boot from USB

When U-Boot loads it gives you two seconds to interrupt the startup by pressing any key. The following command can be used to boot via usb:

run bootcmd_usb0

Other useful commands

boot
reset
poweroff
ls nvme 0:4 /