How to Install and Configure Highly Available HA Kubernetes Cluster with kubeadm
This article describes How to Install and Configure Highly Available HA Kubernetes Cluster with kubeadm.
Kubernetes is a portable, extensible, open-source platform for managing containerized workloads and services, that facilitates both declarative configuration and automation. It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.
The name Kubernetes originates from Greek, meaning helmsman or pilot. Google open-sourced the Kubernetes project in 2014.
Containers are similar to VMs, but they have relaxed isolation properties to share the Operating System (OS) among the applications. Therefore, containers are considered lightweight. Similar to a VM, a container has its own filesystem, CPU, memory, process space, and more. As they are decoupled from the underlying infrastructure, they are portable across clouds and OS distributions.
Containers are a good way to bundle and run your applications. In a production environment, you need to manage the containers that run the applications and ensure that there is no downtime.
Kubernetes provides you with:
-Service discovery and load balancing
-Storage orchestration
-Automated rollouts and rollbacks
-Automatic bin packing
-Self-healing
-Secret and configuration management
A Kubernetes cluster consists of a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node.
The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.
The Control Plane’s components make global decisions about the cluster (for example, scheduling), as well as detecting and responding to cluster events (for example, starting up a new pod when a deployment’s replicas field is unsatisfied).
kube-apiserver
The API server is a component of the Kubernetes control plane that exposes the Kubernetes API. The API server is the front end for the Kubernetes control plane.
etcd
Consistent and highly-available key value store used as Kubernetes’ backing store for all cluster data.
kube-scheduler
Control plane component that watches for newly created Node with no assigned node, and selects a node for them to run on.
Factors taken into account for scheduling decisions include: individual and collective resource requirements, hardware/software/policy constraints, affinity and anti-affinity specifications, data locality, inter-workload interference, and deadlines.
kube-controller-manager
Control Plane component that runs controller processes.
Logically, each controller is a separate process, but to reduce complexity, they are all compiled into a single binary and run in a single process.
cloud-controller-manager
cloud-controller-manager runs controllers that interact with the underlying cloud providers. The cloud-controller-manager binary is an alpha feature introduced in Kubernetes release 1.6.
Node components run on every node, maintaining running pods and providing the Kubernetes runtime environment.
kubelet
An agent that runs on each node in the cluster. It makes sure that containers are running in a Pod.
kube-proxy
kube-proxy is a network proxy that runs on each node in your cluster, implementing part of the Kubernetes Service concept.
Container Runtime
The container runtime is the software that is responsible for running containers.
You can find main steps in below:
*Installing the client tools
*Installing the HAProxy load balancer
*Generating the TLS certificates
*Preparing the nodes for kubeadm
*Installing and configuring Etcd
*Installing and configuring Etcd on the k8sm05 machine (All 5 master)
*Initializing the master nodes
*Configuring kubectl on the client machine
*Joining to Kubernetes Cluster on worker nodes : k8sn01/k8sn02/k8sn03/k8sn04/k8sn05
*Run a Stateless Application Using a Deployment
Now you can find some examples in this video.
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