DevOps Classroom notes 23/Jan/2024

Kubernetes architecture

• K8s has two types of nodes
  • master node
  • node (minion)
• Refer Here for k8s architectural components

Kubernetes installation options

• Self Hosted:
  • Single Node:
    • k3c
    • kind
    • minikube
  • Multinode:
    • binaries
    • kubeadm (lets try this)
    • on cloud (AWS):
      • kubespray Refer Here
    • Baremetal Refer Here

Single Master K8s installation using kubeadm

• Refer Here for official docs
• Create atleast two linux vms 2vcpu 2GB RAM with all internal communication open as specified overhere Refer Here
• Install docker container runtime on both machines.

curl -fsSL https://get.docker.com -o install-docker.sh
sh install-docker.sh
sudo usermod -aG docker ubuntu

• Install kubelet, kubeadm and kubectl on all nodes Refer Here

sudo apt-get update
# apt-transport-https may be a dummy package; if so, you can skip that package
sudo apt-get install -y apt-transport-https ca-certificates curl gpg
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.29/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.29/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl 

• Now lets configure cri-dockerd as k8s doesnot directly communicate with docker Refer Here. Download a deb or rpm package acording to your linux distribution Refer Here

wget https://github.com/Mirantis/cri-dockerd/releases/download/v0.3.9/cri-dockerd_0.3.9.3-0.ubuntu-jammy_amd64.deb
sudo dpkg -i cri-dockerd_0.3.9.3-0.ubuntu-jammy_amd64.deb

• ssh into master node and execute as root user

kubeadm init --cri-socket unix:///var/run/cri-dockerd.sock

• This execution should lead to some output as shown below

To start using your cluster, you need to run the following as a regular user:

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 172.31.21.151:6443 --token uiei66.ibdixnmka1dj6do9 \
        --discovery-token-ca-cert-hash sha256:686d85a23ef071bd338eac409438c43eada59e2fc7f053e369d4e0b4ebed0503

• Now ssh into node1 and execute join command as root user

kubeadm join 172.31.21.151:6443 --token uiei66.ibdixnmka1dj6do9 \
        --discovery-token-ca-cert-hash sha256:686d85a23ef071bd338eac409438c43eada59e2fc7f053e369d4e0b4ebed0503 --cri-socket unix:///var/run/cri-dockerd.sock

• Now in the master node execute kubectl get nodes
  
• Now we need to configure CNI Refer Here
• Lets install weavenet

kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml