Summary
In this Lab exercise we will learn step by step process for creating k8s Cluster
Prerequisites
1. A compatible Linux host (Linux distributions based on Ubuntu, Debian and Red Hat)
2. 2 GB or more of RAM per machine (any less will leave little room for your apps).
3. 2 CPUs or more.
4. Network connectivity between all Nodes in the cluster (Static or DHCP).
5. Unique hostname, MAC address, and product_uuid for every node. See here for more details.
6. Certain ports are open on your machines.
Preparation
1. Disable Swap
Swapoff -a
Nano /etc/fstab
Comment out “#” /swapfile
2. Disable Linux SE (Security Enhanced Linux)
Setenforce 0
Sed -I 's/enforcing/disabled/g' /etc/selinux/config
Grep disabled /etc/selinux/config | grep -v '#'
3. Configure Linux Node’s iptables to correctly see bridged traffic, ensure net.bridge.bridge-nf-call-iptables is set to 1 in sysctl config
—
cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sudo sysctl --system
Step by Step Process
Initializing your control-plane
The control-plane node is the machine where the control plane components run, including etcd (the cluster database) and the API Server (which the kubectl command line tool communicates with)
1. Download latest packages and install
Add Google’s apt repository gpg key
sudo apt-get update && sudo apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
Add the Kubernetes apt repository
cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
Update the package list
sudo apt-get update
2. Install following packages Docker, kubelet, kubeadm and kubectl
sudo apt-get install -y docker.io kubelet kubeadm kubectl kubernetes-cni
Check the status of kubelet and container runtime, docker
sudo systemctl status kubelet.service
sudo systemctl status docker.service
Ensure both are set to start when the system starts up
sudo systemctl enable kubelet.service
sudo systemctl enable docker.service
Note: We no longer wants ‘apt’ to maintain the upgrade of these packages rather depends on Kubernetes to maintain its own updates
sudo apt-mark hold kubelet kubeadm kubectl
Note: Kublet Config files: /var/lib/kubelet/config.yaml
3. Reload the systemd config and docker
sudo systemctl daemon-reload
sudo systemctl restart docker
Install a single control-plane Kubernetes cluster
4. To initialize the control-plane node run:
sudo kubeadm init --pod-network-cidr=10.240.0.0/16
Sample output:
Your Kubernetes control-plane has initialized successfully!
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
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 192.168.1.20:6443 –token ko9j83.f2gdekajw4z280st \
–discovery-token-ca-cert-hash sha256:fc3f3bad62a8f4ea9333bca850dc6bd253d57250e6e39a8436d9428dc4be1884
5. To make kubectl work for your non-root user, run these commands, which are also part of the kubeadm init output:
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
Install a Pod network on the cluster so that your Pods can talk to each other
6. Download & configure Flannel
sudo wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
7. Modify net-conf.json and verify type of network backend being used is set to “host-gw” and that the cluster CIDR (e.g. “10.244.0.0/16”)
This is how net-conf.json should look like
net-conf.json: |
{
“Network”: “10.244.0.0/16”,
“Backend”: {
“Type”: “host-gw”
}
}
8. Apply the Flannel yaml and Validate
kubectl apply -f kube-flannel.yml
Validate Flannel Pod Network
kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-66bff467f8-hvft2 1/1 Running 0 6m
kube-system coredns-66bff467f8-xmc27 1/1 Running 0 6m
kube-system etcd-linuxmaster 1/1 Running 0 6m14s
kube-system kube-apiserver-linuxmaster 1/1 Running 0 6m14s
kube-system kube-controller-manager-linuxmaster 1/1 Running 0 6m14s
kube-system kube-flannel-ds-amd64-jl5v5 1/1 Running 0 46s
kube-system kube-proxy-gh4qr 1/1 Running 0 6m
kube-system kube-scheduler-linuxmaster 1/1 Running 0 6m13s
All the pods will be in ‘Running’ state if the Flannel pod network was deployed.
9. Verify that the Flannel DaemonSet has the NodeSelector applied.
kubectl get ds -n kube-system
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE
kube-flannel-ds-amd64 1 1 1 1 1 <none> 54s
kube-flannel-ds-arm 0 0 0 0 0 <none> 54s
kube-flannel-ds-arm64 0 0 0 0 0 <none> 54s
kube-flannel-ds-ppc64le 0 0 0 0 0 <none> 54s
kube-flannel-ds-s390x 0 0 0 0 0 <none> 54s
kube-proxy 1 1 1 1 1 kubernetes.io/os=linux 6m23s
10. Verify and validate Master status
kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
linuxmaster Ready master 6m41s v1.18.5 10.0.0.x <none> Ubuntu 18.04.4 LTS 5.3.0-1032-azure docker://19.3.6
