buildroot4kubernetes

Build a minimal environment with Buildroot, enough for running kubeadm for Kubernetes.

So basically the "bigger brother" of boot2docker... Or a smaller version of minikube.iso.

* Needed for Kubernetes 1.24 and later only

Written by Anders Björklund (@afbjorklund)

Kernel

• namespaces
• cgroups
• overlayfs
• nat
• bridge
• conntrack
• vxlan

User

• systemd
• glibc (required by systemd)
• docker
• containerd (required by dockerd)
• bash
• iptables
• conntrack (required since 1.18)

Bootable image:

x86_64

192M	output/disk.img.gz

Flashable image:

aarch64

174M	output/sdcard.img.zip

Kubernetes bin:

45M	/usr/bin/kubeadm
46M	/usr/bin/kubectl
116M	/usr/bin/kubelet

Required images:

$ kubeadm config images list
registry.k8s.io/kube-apiserver:v1.28.8
registry.k8s.io/kube-controller-manager:v1.28.8
registry.k8s.io/kube-scheduler:v1.28.8
registry.k8s.io/kube-proxy:v1.28.8
registry.k8s.io/pause:3.9
registry.k8s.io/etcd:3.5.12-0
registry.k8s.io/coredns/coredns:v1.10.1

Additional images:

docker.io/flannel/flannel:v0.23.0

docker pull (gzip):

33M	images/registry.k8s.io/kube-apiserver_v1.28.8
32M	images/registry.k8s.io/kube-controller-manager_v1.28.8
18M	images/registry.k8s.io/kube-scheduler_v1.28.8
27M	images/registry.k8s.io/kube-proxy_v1.28.8
304K	images/registry.k8s.io/pause_3.9
54M	images/registry.k8s.io/etcd_3.5.12-0
16M	images/registry.k8s.io/coredns/coredns_v1.10.1
27M	images/docker.io/flannel/flannel_v0.23.0
203M	total

docker save | xz:

139M	images.txz

Strms  Blocks   Compressed Uncompressed  Ratio  Check   Filename
    1      41    138,8 MiB    630,0 MiB  0,220  CRC32   images.txz

Device layout:

Reference board:

pc (bios)

4.9M	output/images/bzImage
84M	output/images/rootfs.ext2

raspberrypi3-64

18M    output/images/boot.vfat
75M    output/images/rootfs.ext4