Your first Kernel package¶

This tutorial will guide you through packaging your own custom Linux kernel using ukpack.

Requirements¶

You need a Git repository containing your custom kernel tree. For this tutorial, we will use the upstream Linux kernel and modify it to simulate a custom kernel.

Install Dependencies¶

Ensure the required packages are installed:

sudo apt-get update
sudo apt-get install git wget devscripts

Clone Required Repositories¶

First, clone the ukpack repository:

git clone https://kernel.ubuntu.com/forgejo/esmil/ukpack.git

Next, download the upstream Linux kernel source on which the custom kernel is based, in our case this is version 6.6.20:

wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.6.20.tar.xz

Create a Custom Kernel Repository¶

We will now create a new repository for a custom kernel based on the official upstream Linux kernel 6.6.20.

git clone --depth 1 --branch v6.6.20 \
  https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git \
  custom-linux
cd custom-linux/

Make an Example Change to the Kernel¶

To simulate a custom kernel for this tutorial, here we modify the EXTRAVERSION field in the Makefile. Here is where you should apply your changes.

sed -i 's/^EXTRAVERSION =$/EXTRAVERSION = -custom1/' Makefile

Now, commit the change:

git add Makefile
git commit -m "Add custom EXTRAVERSION"

Sync with Upstream Kernel¶

Get the upstream Linux kernel tag corresponding to the version the custom kernel is based on:

git remote add linux-stable \
  https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
git fetch --depth 1 linux-stable tag v6.6.20

This tag will be used to produce a diff between the custom kernel tree and the upstream one.

Define the Kernel Package Configuration¶

Inside the custom-linux directory, create a custom_kernel.toml file:

custom-kernel (6.6.20-1.1ubuntu1) noble; urgency=medium
 * Initial packaging
 -- Your Name <[email protected]> Wed, 12 Mar 2025 14:02:38 +0100
---
arch = "riscv64"
config = "arch/riscv/configs/defconfig"
orig = "v6.6.20"

[pkg.source]
Maintainer = "[email protected]"

Build the Kernel Package¶

Create an output directory and run ukpack:

mkdir ../ukpack.output/
../ukpack/ukpack -o ../linux-6.6.20.tar.xz -t . \
  -d ../ukpack.output/ custom_kernel.toml

Sign the Package¶

Move to the output directory and sign the package:

cd ../ukpack.output
debsign *.changes

Next Steps¶

After signing, you can install or upload the package for further testing.