Using annotations, you can:

• Customize the Kernel that is used (see KernelPath example below)
• Change the guest image (ImagePath)
• Hypervisor (HypervisorPath)
• Firmware (FirmwarePath)
• etc. etc. (All of the annotations are listed in annotations.go)

Using a Custom Kernel

Here is the yaml file I used to apply a custom kernel:

apiVersion: v1
kind: Pod
metadata:
    annotations:
        com.github.containers.virtcontainers.KernelPath: "/usr/share/kata-containers/vmlinuz-4.19.31-40"
    name: kata-example
spec:
  runtimeClassName: kata-qemu

  containers:
  - name: nginx-container
    image: nginx

The metadata key contains the annotations map. All of the annotations are listed in annotations.go on the main repo.

This is documented here: https://github.com/kata-containers/packaging/blob/master/kata-deploy/README.md#docker-quick-start

Using Minikube and Kata

This PR is adding the documentation to get started with minikube: https://github.com/kata-containers/documentation/pull/445#

Using kubeadm

• First, set up a Kubernetes cluster using kubeadm: https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/
• then, https://github.com/kata-containers/packaging/blob/master/kata-deploy/README.md#kubernetes-quick-start

Conclusion

Using the new kata-deploy method, it is very easy to set up a Kubernetes cluster that uses Kata Containers.

For now, let’s look at how I went about doing what I did..

1. You need to go get github.com/kata-containers/packaging repository. (or, git clone if you so prefer.) Be sure to have your $GOPATH properly set!!
2. cd into packaging/kernel directory.
3. I chose the 4.19.31 version of the kernel. Primarily because it was a newer kernel (not too different from the kernel version that comes with the current kata release.) and because it had the RT patches available
4. I changed the kernel_version="" line to kernel_version="4.19.31"

That’s it. We are ready to (1) apply the necessary patches from Kata maintainers to our Kernel of choosing and (2) apply the RT patches:

# download and apply the kata patches to the kernel
./build-kernel.sh setup

cd kata-linux-4.19.31-36
patch -p1<../path-to-extracted-patch/patch-4.19.31-rt18.patch

Wait… we need to first, make menuconfig and enable RT capabilities

General Setup 
  --> Preemption Model
    --> Fully Preemptible Kernel (RT)

Now, we’re ready to build the Kernel and install it*:

./build-kernel.sh setup
sudo ./build-kernel.sh install

Drum Roll please

$ docker run -it --runtime kata-runtime ubuntu bash
root@77cf04fd8290:/# uname -r
4.19.31-rt18
root@77cf04fd8290:/# uname -a
Linux 77cf04fd8290 4.19.31-rt18 #2 SMP PREEMPT RT Mon Apr 29 09:06:08 CEST 2019 x86_64 x86_64 x86_64 GNU/Linux
root@77cf04fd8290:/# 

So proud!!!

Happy Building!!

Note on Kernel Files

vmlinux: uncompressed kernel. | vmlinuz: compressed kernel. | bzImage: located under arch/x86_64/boot/bzImage. Big Zimage. Compressed kernel image.

More info: https://stackoverflow.com/a/22338835/3760442

Acknowledgements

Special thanks to @egernst, @rico and the great team on Slack!! Though this was my first foray into Kata Containers, I must say the folks were very welcoming. Thank you all!!

* I built the kernel (as of the time of writing) using make build -j4 instead of using the build-kernel.sh script but it shouldn’t matter. Just FYI.