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I have successfully installed Ubuntu 20.04 LTS on a Raspberry Pi 4 using the following image: https://ubuntu.com/download/raspberry-pi/thank-you?version=20.04&architecture=arm64+raspi

I want to customize the kernel, however, I have tried various methods but none of them produce a bootable 5.4.0 kernel. The /boot folder isn't standard by any means, so my question is does anyone have any idea to build a custom kernel on Ubuntu on a Raspberry Pi 4 for arm64? Any Ubuntu documentation that pertains to Ubuntu and this hardware would be grateful.

  • I don't think there should be any difficulties when building a custom kernel if you build it a proper way as deb packages. – Pilot6 May 11 at 20:05
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I feel your pain. There is a ton of information around, and most of it is close, but not exactly what you need. I recently succeeded in building 20.04 kernels for the pi 4. My notes are attached here. I'm building the 32-bit version, and I'm not cross-compiling; I'm building on the pi itself.

To customize, edit files under .../debian.raspi/config/

start with a 32GB card (might just barely fit on a 16GB card)

download, install, and update 32-bit (= "armhf") Ubuntu Server 20.04 for Raspberry Pi (preinstalled image)

uncomment the following 2 lines in /etc/apt/sources.list:
deb-src http://ports.ubuntu.com/ubuntu-ports focal main restricted
deb-src http://ports.ubuntu.com/ubuntu-ports focal-updates main restricted

sudo apt update
sudo apt-get build-dep linux linux-image-$(uname -r)   # brings in nearly a gigabyte
sudo apt install libncurses-dev linux-tools-common fakeroot

# these notes assume your build tree will be in ~/kbuild.
# if you'd prefer to put it elsewhere, simply substitute your location for ~/kbuild in all that follows.

mkdir ~/kbuild
cd ~/kbuild
# NOTE: the following git command retrieves the *raspi* branch!
git clone --depth=1 git://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/focal -b raspi

# intial build - takes 2 hours 20 minutes, creates 7 .deb files in ~/kbuild
cd ~/kbuild/focal
fakeroot debian/rules clean
fakeroot debian/rules binary-headers binary binary-perarch

# install and run the newly-built kernel:
sudo apt install libunwind8 linux-tools-common libdw1
cd ~/kbuild
sudo dpkg -i *.deb
sync; sudo reboot

# rebuild - takes 30 minutes
cd ~/kbuild/focal
rm debian/stamps/stamp-build*
rm -rf debian/linux-libc-dev/usr/include/arm-linux-gnueabihf
rm -rf debian/build/build-raspi/_____________________________________________dkms
# if you've changed any header files, add binary-headers to the following line:
fakeroot debian/rules binary binary-perarch
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