Completek8s Classroomnotes 10/Sep/2023

Certified Kubernetes Administrator

Cluster Architecture, Installation and Configuration

• We can setup HA Cluster using two topologies
  • Stacked etcd
  • External etcd
• Stacked etcd:
  • The distributed data storage (etcd) is part of nodes managed by kubeadm
  • Each control plane node has kube-apiserver, kube-scheduler, kube controller manager & etcd node
    
• External etcd:
  • This HA Cluster will have external etc where the data is distributed and stored
  • Each control plane node has kube-apiserver, kube-scheduler, kube controller manager
  • This is more HA and it needs minimum six nodes to setup master

Lab setup:

• We will be creating 3 worker nodes and 3 master nodes to be part of control plane
• The load Balancer will be software based load balancer (HAProxy)

Steps

• Create 3 master nodes (master-node-1, master-node-2, master-node-3)
• login into any master
• Ensure master-node-1 has the private key to connect other nodes copied into it
• Install tmux

sudo apt update
sudo apt install tmux -y

• Launch tmux

# rename window
ctrl + b ,
# create a vertical split
ctrl + b %

# create a horizontal split
ctrl + b "

# To move across panes verticall
ctrl + b  (arrows)

• Refer Here for help
• The node info so far

Role	Name Tag	FQDN	IP
Master	master-node-1	ip-172-31-48-55.ec2.internal	172.31.48.55
Master	master-node-2	ip-172-31-50-145.ec2.internal	172.31.50.145
Master	master-node-3	ip-172-31-55-80.ec2.internal	172.31.55.80
Load Balancer	haproxy	ip-172-31-42-89.ec2.internal	172.31.42.89

• Setup loadbalancer

sudo apt update
sudo apt install haproxy -y

• Since api-server runs on port 6443, Let do the following config
• Take backup of haproxy config /etc/haproxy/haproxy.cfg

sudo cp /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy.cfg-orig

• Now replace the contents fo haproxy.cfg with the following contents

frontend kubernetes-frontend
    bind 172.31.42.89:6443
    mode tcp
    option tcplog
    default_backend kubernetes-backend
backend kubernetes-backend
    mode tcp
    option tcp-check
    balance roundrobin
    server ip-172-31-48-55.ec2.internal 172.31.48.55:6443
    server ip-172-31-50-145.ec2.internal 172.31.50.145:6443
    server ip-172-31-55-80.ec2.internal 172.31.55.80:6443

• reload the daemon and start haproxy

sudo systemctl daemon-reload
sudo systemctl restart haproxy.service

• Using tmux panes execute the following commands on all master nodes to install docker, kubelet, kubectl and kubeadm

cd /tmp
curl -fsSL https://get.docker.com -o install-docker.sh
sh install-docker.sh
wget https://github.com/Mirantis/cri-dockerd/releases/download/v0.3.4/cri-dockerd_0.3.4.3-0.ubuntu-jammy_amd64.deb
sudo dpkg -i cri-dockerd_0.3.4.3-0.ubuntu-jammy_amd64.deb
sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates curl
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.28/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:/v1.28/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

• kubeadm accepts the following named arguments
  • –control-plane-endpoint: can be used to set the shared endpoint for all control-plane nodes
  • –apiserver-advertise-address: can be used to set the advertise address for this particular control-plane node’s API server
  • –cri-socket: to set the cri for container runtime
  • –pod-network-cidr: to set the pod network range
• Login into any of the master nodes master-node-1

kubeadm init --control-plane-endpoint="172.31.42.89:6443" \
        --upload-certs \
        --apiserver-advertise-address=172.31.48.55 \
        --pod-network-cidr=192.168.0.0/16 \
        --cri-socket="unix:///var/run/cri-dockerd.sock"

• Now in other nodes also execute join commands as shown in class, install any suitable cni plugin
• now get nodes