A Complete Guide to Kubernetes Container

Introduction

Kubernetes stands out as a pivotal solution that streamlines the deployment and orchestration of applications within containerised environments. The projected market share of Kubernetes container technology for 2023 stands at 24.4%. Initially developed in 2014 by Google Lab, it was nicknamed K8s. 

As an open-source platform, Kubernetes facilitates the orchestration of containers to streamline the deployment, scaling, and management of applications across environments such as cloud-native and physical settings. 

This article aims to provide readers with a comprehensive understanding of containers and explore how enterprises can leverage tools like Kubernetes to enhance their operational efficiency and scalability.

Basics of Kubernetes

A Kubernetes cluster comprises worker nodes responsible for running containerised applications. Each cluster has a minimum of one worker node that hosts Pods, which are components of the application workload. The control plane oversees the worker nodes and Pods typically operating across machines to ensure fault tolerance and high availability.

Architecture of Kubernetes

The architecture of Kubernetes is highly intricate and includes two components. They are the following:

Controller plane

The control plane plays a role in managing the Kubernetes cluster. It also acts as a gateway for administrative tasks within the Kubernetes infrastructure. Multiple components can be deployed to enhance fault tolerance. Key elements include:

• API server: Acts as the entry point for all REST commands that govern the cluster.
• Scheduler: Responsible for distributing tasks across nodes based on resources.
• Etcd: Stores configuration information, handles network rules, and forwards ports

Worker/agent nodes

Worker nodes manage container networking, communicate with the controller node, and allocate resources to containers. The main components include:

• Kubelet: Ensures containers within a Pod run based on configurations from the API server.
• Docker container: Executes configured pods on each worker node.
• Kube proxy: Functions as a load balancer and network proxy on a worker node.
• Pods: Comprise one or more containers that run collectively on nodes.

Key components of Kubernetes

The architecture of Kubernetes is divided into two main sections: Control Plane Components and Node Components.

Control plane components

Following are the control plane components of Kubernetes:

• Kube apiserver: Exposes the Kubernetes API. Serves as the end of the control plane. It can scale horizontally by deploying instances.
• Etcd: It serves as a key-value store for all cluster data, ensuring consistency and high availability. It is crucial to have plans for etcd data.
• Kube scheduler: Assigns nodes to created Pods based on resource requirements and constraints.
• Kube controller manager: Manages controller processes like the Node controller, Job controller, and ServiceAccount controller.
• Cloud controller manager: Integrates the cluster with cloud provider APIs and operates cloud-specific controllers such as the Node, Route, and Service controllers.

Node components

Following are the node components of Kubernetes:

• Kubelet: The kubelet ensures containers run within Pods on each node based on the provided PodSpecs.
• Kube proxy manages network rules for communication to and from Pods, implementing the Kubernetes Service concept.
• Container runtime: The container runtime oversees the execution and lifecycle of containers. Kubernetes supports container runtimes such as containers and CRI O.

Kubernetes objects

These are entities in your cluster that reflect its state. They specify which containerised applications run the allocated resources and their behaviour policies, such as restarts and upgrades. When an object is created, Kubernetes ensures it aligns with the desired state.

Deploying applications with Kubernetes

Learn how to deploy sample Kubernetes applications, automate the deployment process with the Harness CI/CD platform, and effortlessly streamline software delivery.

Test the sample application locally

Before deploying to Kubernetes, ensuring the sample application functions correctly in a local environment is crucial. Follow these steps:

• Fork and clone the sample notes application from the GitHub repository.
• Navigate to the application folder using the command line.
• Install dependencies using `npm install`.
• Run the application locally with `node app.js` to ensure it works correctly.

Containerise the application

The following steps are to guide you on how to containerise the application:

• Utilise the provided Dockerfile in the sample application repository to containerise the application.
• Build, tag, and push the Docker image to a container registry of choice, such as Docker Hub.

Create or access a Kubernetes cluster

Follow the steps mentioned below to create or access a Kubernetes cluster:

• Ensure access to a Kubernetes cluster from a cloud provider or locally using Minikube or Kind.
• Ensure Neat and Clean Kubernetes Manifest Files
• Verify the deployment.yaml and service.yaml files are correctly configured to deploy and expose the application.
• Apply the manifest files using `kubectl apply -f deployment.yaml` and `kubectl apply -f service.yaml`.
• Verify proper pod deployment with `kubectl get pods.`

Automate deployment using Harness

Streamline the deployment process with Harness by following the given steps:

• Sign up for Harness and create a project.
• Select the Continuous Delivery module and start a free plan.
• Connect to the Kubernetes environment using a Delegate.
• Download the Delegate YAML file and install it on the Kubernetes cluster.

Configure the service and add manifest details.

Configure and enhance efficiency by automating the CD process through the following steps:

• Create a pipeline and ensure all connections are successful.
• Run the pipeline for successful deployment.
• Automate Continuous Deployment (CD) Process
• Use Triggers in Harness to automate the CD process.
• When authorised personnel push new code to the repository, the pipeline triggers CD automatically.

Monitoring and logging in Kubernetes

Monitoring and logging play roles in Kubernetes as they help understand system operations status and resolve issues effectively. However, these components are not mandatory in Kubernetes, and third-party tools or cloud services may need adjustments. Kubernetes can generate and collect logs from pods, nodes, and controllers. Integrating a third-party logging solution can enhance log analysis and visualisation.

Networking in Kubernetes

If there aren't any deliberate network segmentation regulations in place, Kubernetes enforces the following basic requirements on any networking implementation:

• Without NAT agents, pods can communicate with every pod on any other node.
• System daemons and kubelets can talk with every other pod on a node.

Securing Kubernetes deployments

Ensuring the security of your Kubernetes deployments is essential to safeguard your cluster against malicious access. Here are some recommended practices for enhancing the security of your Kubernetes environment:

• Control access to the Kubernetes API: utilise Transport Layer Security (TLS) to secure all.
• API traffic: Ensure all API communication within the cluster is encrypted via TLS by default. Note that enabling TLS by default requires additional configuration in Kubernetes.
• API authorisation: Following authentication, each API request must undergo an authorisation validation. Kubernetes provides a built-in role-based access control (RBAC) feature that maps users or groups to predefined roles with permissions.
• Securing images and containers: Ensure approved images following your organisation's guidelines are permitted to operate. This helps prevent the execution of harmful containers.
• Administrative boundaries: Establish boundaries among resources. Utilise namespaces to segregate workloads and enforce access controls.
• Network segmentation: Set up network segmentation to limit communication between pods and services. Use Network Policies to establish regulations for outgoing traffic.

Managing storage in Kubernetes

In a cloud or cluster setting, it provides the services and management tools for container deployment, operation, and scalability. With maintenance, Kubernetes storage frameworks can automatically offer optimal storage solutions for applications with minimal administrative burden. Storage managers can oversee types of nonpersistent data in a Kubernetes cluster using Kubernetes storage, which proves beneficial for managing containerised environments.

Advanced Kubernetes features

Once you're familiar with the basics of Kubernetes, explore these advanced features:

• Sidecar container Kubernetes: Useful for tasks like logging or authentication without modifying the primary container. A sidecar container in Kubernetes is a container that launches and runs independently of the primary application container. The Kubernetes init container executes before the app container when a pod is initialised.
• Helm charts: This tool uses charts that describe packages and contain Kubernetes manifest templates. It facilitates the quick and easy deployment of applications with preconfigured charts.
• Custom controllers: Controllers are loops that manage the state of your system or resources. Custom controllers handle tasks beyond standard controllers, like dynamically reloading configurations.

Conclusion

Kubernetes has revolutionised the way organisations manage containerised applications, offering unmatched scalability, flexibility, and efficiency. By automating deployment, scaling, and operations of application containers, Kubernetes enables businesses to innovate rapidly while maintaining robust system reliability. 

Mastering Kubernetes empowers teams to optimise resource usage, streamline workflows, and achieve seamless integration with existing cloud infrastructures. 

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