Customizing the Kernel

Guide on how to customize the kernel used by Talos Linux.

The installer image contains ONBUILD instructions that handle the following:

the decompression, and unpacking of the initramfs.xz
the unsquashing of the rootfs
the copying of new rootfs files
the squashing of the new rootfs
and the packing, and compression of the new initramfs.xz

When used as a base image, the installer will perform the above steps automatically with the requirement that a customization stage be defined in the Dockerfile.

Build and push your own kernel:

git clone https://github.com/talos-systems/pkgs.git
cd pkgs
make kernel-menuconfig USERNAME=_your_github_user_name_

docker login ghcr.io --username _your_github_user_name_
make kernel USERNAME=_your_github_user_name_ PUSH=true

Using a multi-stage Dockerfile we can define the customization stage and build FROM the installer image:

FROM scratch AS customization
# this is needed so that Talos copies base kernel modules info and default modules shipped with Talos
COPY --from=<custom kernel image> /lib/modules /kernel/lib/modules
# this copies over the custom modules
COPY --from=<custom kernel image> /lib/modules /lib/modules

FROM ghcr.io/siderolabs/installer:latest
COPY --from=<custom kernel image> /boot/vmlinuz /usr/install/${TARGETARCH}/vmlinuz

When building the image, the customization stage will automatically be copied into the rootfs. The customization stage is not limited to a single COPY instruction. In fact, you can do whatever you would like in this stage, but keep in mind that everything in / will be copied into the rootfs.

To build the image, run:

DOCKER_BUILDKIT=0 docker build --build-arg RM="/lib/modules" -t installer:kernel .

Note: buildkit has a bug #816, to disable it use DOCKER_BUILDKIT=0

Now that we have a custom installer we can build Talos for the specific platform we wish to deploy to.