Customizing the Kernel

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.