This is a guide for building an arm64 Debian distribution for the Raspberry Pi model 4. Development of this guide was done on Fedora Linux x86_64, however any distribution will work.
Please make sure your Raspberry Pi 4 has the latest bootloader installed. Follow the instructions at Updating the Bootloader.
- Installing prerequisites
- Format SD card
- Install base system root filesystem
- Build and install the Linux kernel
- Install firmware
- Edit some configuration files
- Finalization
- Post-Install
These tools are needed to cross-compile the Linux kernel for arm64 and build the base Debian system.
sudo dnf group install "C Development Tools and Libraries" "Development Tools"
sudo dnf install openssl-devel qemu-user-static gcc-aarch64-linux-gnu binutils-aarch64-linux-gnu debootstrap
The SD card needs a FAT partition for /boot to reside on and the remaining space will be used for /. Replace /dev/sdb with
the path that corresponds to your SD card for the rest of the guide.
sudo fdisk /dev/sdb
Create a 200-300MiB primary partition 1 with partition type c, then create a primary partition 2 with the remaining space.
It can keep the default partition type 83.
Verify your partition table looks similar to this and write the table.
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 411647 409600 200M c W95 FAT32 (LBA)
/dev/sdb2 411648 60751871 60340224 28.8G 83 Linux
Create a FAT32 filesystem on partition 1 and an ext4 filesystem on partition 2.
sudo mkfs.vfat -F32 /dev/sdb1
sudo mkfs.ext4 /dev/sdb2
We will use /mnt to mount the SD card.
sudo mount /dev/sdb2 /mnt
sudo mkdir /mnt/boot
sudo mount /dev/sdb1 /mnt/boot
We will use debootstrap to download the base Debian system and finish the package configuration inside a chroot.
debootstrap will download just enough packages to let the system boot, but if you know which additional packages you
will need, then use the --include flag to add them here.
I would recommend starting with --include=dbus,openssh-server,man-db,ntp,locales
You can also install packages from inside a chroot later.
sudo debootstrap --arch=arm64 --foreign stable /mnt http://deb.debian.org/debian
sudo cp $(which qemu-aarch64-static) /mnt/usr/bin
sudo chroot /mnt /debootstrap/debootstrap --second-stage
You may need to update which branch is currently being worked on. Just check the branches tab on Github.
git clone --depth=1 -b rpi-5.6.y https://github.com/raspberrypi/linux
mkdir linux-build
cd linux
make O=../linux-build ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bcm2711_defconfig
make O=../linux-build ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- modules Image dtbs
sudo make O=../linux-build ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- INSTALL_MOD_PATH=/mnt modules_install
sudo make O=../linux-build ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- INSTALL_DTBS_PATH=/mnt/boot dtbs_install
sudo mv /mnt/boot/broadcom/* /mnt/boot # rpi documentation says .dtb files should be alongside start4.elf, i.e. in /boot
sudo rmdir /mnt/boot/broadcom
sudo cp ../linux-build/arch/arm64/boot/Image /mnt/boot/kernel8.img
There is some proprietary firmware that we cannot build from source so we will yank it from here.
The additional .elf and .dat files can be used if you know what you are doing, but they are unnecessary to get the
system booting. Read
Boot Folder Contents for more information.
git clone --depth=1 https://github.com/raspberrypi/firmware
sudo cp firmware/boot/fixup4.dat /mnt/boot
sudo cp firmware/boot/start4.elf /mnt/boot
Just copy the entire command into your terminal, or modify the files to match the text between the EOF's.
fstab tells the system how to mount the partitions during boot. Feel free to modify this file as you see fit, but this is sufficient.
sudo tee /mnt/etc/fstab > /dev/null << EOF
proc /proc proc defaults 0 0
/dev/mmcblk0p1 /boot vfat defaults 0 2
/dev/mmcblk0p2 / ext4 defaults,noatime 0 1
EOF
Kernel command line parameters. Once again, feel free to modify the kernel parameters as you see fit. I found these were sufficient for a clean boot.
sudo tee /mnt/boot/cmdline.txt > /dev/null << EOF
root=/dev/mmcblk0p2 rootfstype=ext4 rootwait
EOF
This setting tells the RPI to load kernel8.img as a 64bit kernel.
More information about this file can be found at
The config.txt file.
sudo tee /mnt/boot/config.txt > /dev/null << EOF
arm_64bit=1
EOF
Enable DHCP on ethernet. You can set up the network however you want.
sudo tee /mnt/boot/usr/lib/systemd/network/eth.network > /dev/null << EOF
[Match]
Name=eth*
[Network]
DHCP=ipv4
EOF
At this point, the system is configured and should boot without errors, but there's a few more configuration steps we could take from inside a chroot.
sudo chroot /mnt /bin/bash -l
passwd # set root password
dpkg-reconfigure locales # select your locale
systemctl enable systemd-networkd
systemctl set-default multi-user
If you need an initial ramdisk, one can be configured now. Enter the chroot with /dev, /sys, and /proc mounted.
sudo mount -t proc /proc /mnt/proc/
sudo mount --rbind /sys /mnt/sys/
sudo mount --rbind /dev /mnt/dev/
sudo chroot /mnt /bin/bash -l
apt-get install dracut
Add dracut configuration. Some of dracut's modules will activate automatically if certain programs are found, eg btrfs.
tee /etc/dracut.conf.d/rpi-initrd.conf > /dev/null << EOF
kernel_cmdline="root=/dev/mmcblk0p2 rootwait"
EOF
Generate the initrd with the installed kernel. Use ls /lib/modules to find the kernel version.
dracut --kver <version>
dracut --kver <version> /boot/initrd.img
Point the rpi's firmware to the initrd.
echo "initramfs initrd.img followkernel" | tee -a /boot/config.txt
Consider adding a user account with adduser and finally,
exit
sudo rm /mnt/usr/bin/qemu-aarch64-static
Consider copying all files from /mnt to another folder as backup. Perhaps we should have installed everything into
a folder in the first place, then copied that over to the SD card. Oh well. We already made it this far.
Please allow umount to finish before unplugging your SD card to prevent file corruption.
sudo umount /mnt/boot
sudo umount /mnt
Steps to update the kernel are similar to the initial kernel build steps.
sudo apt-get install build-essential flex bison bc
git clone --depth=1 -b rpi-5.6.y https://github.com/raspberrypi/linux
mkdir linux-build
cd linux
make O=../linux-build ARCH=arm64 bcm2711_defconfig
make O=../linux-build ARCH=arm64 modules Image dtbs
sudo make O=../linux-build ARCH=arm64 INSTALL_MOD_PATH=/ modules_install
sudo make O=../linux-build ARCH=arm64 INSTALL_DTBS_PATH=/boot dtbs_install
sudo mv /boot/broadcom/* /boot # rpi documentation says .dtb files should alongside start4.elf, i.e. in /boot
sudo rmdir /boot/broadcom
sudo cp ../linux-build/arch/arm64/boot/Image /boot/kernel8.img
After a kernel upgrade the initrd can also be updated if being used. Consider keeping a couple older initrd's around just in case something goes wrong.
sudo dracut --kver <new version>
sudo dracut --kver <new version> /boot/initrd.img
sudo rm /boot/initrd.img-<old version>
Congratulations. Your raspberry pi should now be running a fully functional 64bit OS, as it should.
Please submit an Issue if you found errors in the guide or want me to add something. Brady Dean