2020-07-10 afbjorklund

Proof-of-Concept Release

The early releases from the “buildroot4kubernetes” project are up:

https://github.com/afbjorklund/buildroot4kubernetes

• amd64 (pc_x86_64_bios)
• arm64 (raspberrypi3_64)

Release Files

amd64: disk.img.gz images.iso

arm64: sdcard.img.zip images.tar.gz

Components

It is similar to “boot2docker”, but also adds kubernetes components:

• Docker engine (dockerd)
• Docker containerd (containerd)

• Docker client (docker)

• SSH server (sshd)

• Bash shell (bash)

• Kubernetes installer (kubeadm)
• Kubernetes service (kubelet)

• Kubernetes client (kubectl)

• CRI tools (crictl) - Container Runtime Interface
• CNI plugins (/opt/cni) - Container Network Interface

Docker Images

Everything else is run from containers, after the initial bootstrap:

• kube-controller-manager
• kube-apiserver
• etcd
• kube-scheduler
• kube-proxy
• coredns

There is also a default CNI plugin included, “flannel” (using VXLAN).

• flannel

As well as the special “infra” container which is used by the k8s pods.

• pause

Usage

The idea is that the user should have just enough to bootstrap Kubernetes…

Either a new control plane (kubeadm init) or a worker (kubeadm join):

• https://kubernetes.io/docs/reference/setup-tools/kubeadm/kubeadm-init/

• https://kubernetes.io/docs/reference/setup-tools/kubeadm/kubeadm-join/

If wanting to deploy the network plugin, there are some extra steps needed:

kubeadm init --pod-network-cidr=10.244.0.0/16

export KUBECONFIG=/etc/kubernetes/admin.conf
kubectl apply -f /etc/kubernetes/flannel.yml

You could also use a different network plugin, see kubeadm documentation

• Canal https://github.com/projectcalico/canal
• Calico https://github.com/projectcalico/calico
• Weave https://github.com/weaveworks/weave

Differences

These are the biggest differences to boot2podman kubernetes:

• Buildroot (instead of Tiny Core Linux)
• Systemd (instead of init(1) and cgroupfs)

• Raspberry Pi support (in addition to KVM)

• docker (instead of podman)
• containerd (instead of cri-o)
• kubernetes/k8s (instead of k3s)

This was described further in some earlier posts on the topic:

• Buildroot Kubernetes

• Lightweight Kubernetes

As well as some other about software and hardware architecture:

• Three Sizes of Cluster

• Three Sizes of Image

Future

Some future development paths to be investigated further:

• Raspberry Pi 2 (armv7)

• Administration (like “machine”)