Kubernetes (also known as "K8s") is an open-source platform for automating the deployment, scaling, and management of containerized applications. Containerized applications are packages of software that include all of the necessary code and dependencies required to run, which makes them easy to deploy and run consistently across different environments.
Kubernetes was designed to help developers and operations teams manage and scale containerized applications by providing a set of tools and APIs for deploying, managing, and scaling applications. It can run on top of various infrastructure platforms, such as bare metal servers, virtual machines, and public cloud providers.
Some of the key features of Kubernetes include:
Deployment and scaling of containerized applications: Kubernetes makes it easy to deploy and scale containerized applications by allowing you to define the desired state of your application and automatically ensuring that the actual state matches the desired state.
Load balancing and service discovery: Kubernetes includes built-in support for load balancing and service discovery, which makes it easy to expose your application to other services and users.
Self-healing: Kubernetes includes built-in mechanisms for automatically replacing or restarting failed containers, helping to ensure that your application stays up and running even in the face of failures.
Monitoring and logging: Kubernetes includes built-in support for monitoring and logging, which makes it easier to track the health and performance of your application and identify issues.
Overall, Kubernetes is a powerful platform that can help developers and operations teams manage and scale containerized applications more effectively.
SD CARDS
To start let's use the Buster lite image from the Raspberry Pi Foundation
Flash Buster lite to the micro sd cards.
This is documented in many places the oficial guide is here https://www.raspberrypi.org/documentation/installation/installing-images/README.md
DOCKER
We need a container runtime interface
This is how we installed Docker (Buster Lite 2020-02-05-raspbian-buster-lite)
curl -fSLs https://get.docker.com |sudo sh
We want to use docker as a non root user
sudo usermod -aG docker pi
KUBEADM
Install kubeadm all nodes
We need the legacy binaries
sudo apt install -y iptables arptables ebtables
After installing the legacy binaries we need to switch to them
sudo update-alternatives --set iptables /usr/sbin/iptables-legacy
sudo update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy
sudo update-alternatives --set arptables /usr/sbin/arptables-legacy
sudo update-alternatives --set ebtables /usr/sbin/ebtables-legacy
We will need curl and apt-transport-https (enable deb https lines in sources file)
sudo apt install -y apt-transport-https curl
Now we setup the kuberneties repo
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
sudo apt update && sudo apt install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
sudo kubeadm config images pull
Master Node
On the Master node only lets initiate K8s
sudo kubeadm init --pod-network-cidr=10.200.0.0/16
If you want a user other than root you need to give that user permissions
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Install Flannel
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
WORKER NODES
When you init the last few lines will be similar to the following
You can now join any number of machines by running the following on each node
as root:
kubeadm join 10.200.0.64:6443 --token <mytoken> --discovery-token-ca-cert-hash sha256:<myhash>
Verify that your node has joined by issuing the following command on the master
kubectl get nodes
The output will look something like the following
NAME STATUS ROLES AGE VERSION
11e9d2ef Ready <none> 19h v1.17.3
2ebc89ea Ready <none> 22h v1.17.3
31b81f1b Ready <none> 3h33m v1.17.3
3386756e Ready master 23h v1.17.3
33e9bb39 Ready <none> 3h30m v1.17.3
47227a70 Ready <none> 22h v1.17.3
77ab07f5 Ready <none> 3h57m v1.17.3
9fc14109 Ready <none> 19h v1.17.3
b837e9ca Ready <none> 4h9m v1.17.3
kubectl get all -n kube-system
I have decided to go a different route than k8s, It has too much overhead for the pi's to run efficiently.
References
Raspberry Pi foundation Buster Lite
https://www.raspberrypi.org/downloads/raspbian/
Kubernetes documentation:
https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/install-kubeadm/
Alex Ellis : Docker on Buster Lite
https://blog.alexellis.io/how-to-fix-docker-for-raspbian-buster/