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.

Interface	Implementation	Notes
Container Runtime	docker	`cri-dockerd`*
Container Networking	flannel	VXLAN backend
Container Storage	nfs	ReadWriteMany

* 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:

155M	output/disk.img.gz

Kubernetes bin:

43M     kubeadm
45M     kubectl
113M    kubelet

Required images:

$ kubeadm config images list
k8s.gcr.io/kube-apiserver:v1.23.0
k8s.gcr.io/kube-controller-manager:v1.23.0
k8s.gcr.io/kube-scheduler:v1.23.0
k8s.gcr.io/kube-proxy:v1.23.0
k8s.gcr.io/pause:3.6
k8s.gcr.io/etcd:3.5.1-0
k8s.gcr.io/coredns/coredns:v1.8.6

docker images:

REPOSITORY                           TAG        IMAGE ID       CREATED         SIZE
k8s.gcr.io/kube-apiserver            v1.23.0    e6bf5ddd4098   2 weeks ago     135MB
k8s.gcr.io/kube-controller-manager   v1.23.0    37c6aeb3663b   2 weeks ago     125MB
k8s.gcr.io/kube-scheduler            v1.23.0    56c5af1d00b5   2 weeks ago     53.5MB
k8s.gcr.io/kube-proxy                v1.23.0    e03484a90585   2 weeks ago     112MB
k8s.gcr.io/pause                     3.6        6270bb605e12   4 months ago    683kB
k8s.gcr.io/etcd                      3.5.1-0    25f8c7f3da61   7 weeks ago     293MB
k8s.gcr.io/coredns/coredns           v1.8.6     a4ca41631cc7   2 months ago    46.8MB

docker pull (gzip):

31M	images/k8s.gcr.io/kube-apiserver_v1.23.0
29M	images/k8s.gcr.io/kube-controller-manager_v1.23.0
15M	images/k8s.gcr.io/kube-scheduler_v1.23.0
37M	images/k8s.gcr.io/kube-proxy_v1.23.0
284K	images/k8s.gcr.io/pause_3.6
94M	images/k8s.gcr.io/etcd_3.5.1-0
13M	images/k8s.gcr.io/coredns/coredns_v1.8.6
20M	images/quay.io/coreos/flannel_v0.14.0
237M	total

docker save | xz:

162M	images.txz

Strms  Blocks   Compressed Uncompressed  Ratio  Check   Filename
    1      51    161,5 MiB    789,9 MiB  0,204  CRC32   images.txz

Device layout:

QEMU	File	Media	Device	Used for	Size
-hda	disk.img	disk	/dev/sda	Persistent `/var`	20g
-hdb	data.img	disk	/dev/sdb	Persistent `/data`	5g
-hdc	buildroot.iso	cdrom		Buildroot booting	137m
-hdd	images.iso	cdrom	/dev/sdc	Kubernetes images	160m

Reference board:

pc (bios)

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

whooo/buildroot4kubernetes

buildroot4kubernetes