Docker in OpenShift: Managing and Deploying Containerized Applications with Kubernetes

Docker in OpenShift

OpenShift is an enterprise-class Kubernetes container orchestration platform built by Red Hat. It extends Kubernetes with additional capabilities for managing containerized applications, making them more secure, scalable, and efficient. OpenShift is tightly integrated with Docker, allowing users to build, deploy and manage Docker containers in Kubernetes-based environments.

1. What is OpenShift?

OpenShift is a comprehensive Platform as a Service (PaaS) that provides a complete solution for building, deploying and scaling containerized applications using Kubernetes as the core orchestrator. It adds multiple security, management and automation layers on top of Kubernetes, with features such as integrated CI/CD pipelines, multi-tenancy and a rich web console.

Kubernetes focuses on orchestration and management of containers, while OpenShift provides developers and operators with an enterprise-grade solution with user-friendly features.

Key features of OpenShift

• Kubernetes-based orchestration: OpenShift uses Kubernetes for container orchestration, providing the power of Kubernetes with greater security and ease of use.
• Integrated CI/CD pipeline: OpenShift includes tools for automating the building, testing, and deployment of applications.
• Self-service developer platform: Developers can build and deploy applications with minimal intervention from system administrators.
• Enhance security: OpenShift enforces strict security policies, including automatic image scanning for vulnerabilities and role-based access control (RBAC).
• multi-tenant: OpenShift supports the deployment of multiple applications in isolated environments (projects), enabling multi-user collaboration.

2. Docker in OpenShift: How it works

OpenShift is built on top of Docker to manage containerized applications using Docker image As a format for packaging and distributing applications. OpenShift handles these Docker containers with additional security and operational tools to ensure they operate effectively in production environments.

Key components of OpenShift

• OpenShift node: Each node in an OpenShift cluster is a server running Docker and a Kubernetes instance used to orchestrate containers.
• pod: Pod is the smallest deployable unit in OpenShift, containing one or more containers. These containers are usually Docker containers.
• OpenShift build: Build is the process of creating a Docker image from application code. OpenShift support Source to Image (S2I)which allows creating images directly from source code.
• OpenShift deployment: Manage application deployment and expansion. It ensures that the required number of Pods are running according to the specified configuration.

OpenShift interaction with Docker

1. Docker image: In OpenShift, Docker images are used as the basis for containerized applications. These images are stored in the login and can be pulled for deployment in OpenShift.
2. OpenShift build: OpenShift can use its application code to create Docker images from your application code S2I Process or from pre-built images. When you commit changes to the repository, OpenShift automatically builds a new Docker image.
3. Docker runtime: OpenShift uses Docker (or any CRI-compatible execution time) to run containers within pods. Docker manages the life cycle of a container, from creation to execution of an application within the container.
4. image stream:OpenShift uses image stream Manage Docker images and integrate with its internal image registry.

3. Using Docker with OpenShift

Step 1: Set up the OpenShift cluster

You can install OpenShift on a variety of platforms, including native systems (using Minishift), native systems, or cloud providers such as AWS and Azure. The easiest way to get started with OpenShift is to use mini shift Tool for setting up native OpenShift clusters.

minishift start

Alternatively, you can deploy OpenShift on a Kubernetes cluster using the following command OpenShift Origins Or use Red Hat OpenShift Container Platform for enterprise environments.

Step 2: Push the Docker image to OpenShift

OpenShift uses its own registry to store Docker images. You can push Docker images to an OpenShift registry or an external Docker registry.

1. Tag the Docker image: Mark your Docker image to be OpenShift compliant.

   docker tag my-app my-openshift-registry.example.com/my-project/my-app:v1

1. Log into the OpenShift registry: Using the OpenShift CLI (oc) to log in and push the image.

   docker login -u myuser -p mypassword my-openshift-registry.example.com

1. Push pictures: Push the tagged Docker image to the OpenShift registry.

   docker push my-openshift-registry.example.com/my-project/my-app:v1

Step 3: Build and deploy the application on OpenShift

1. Create a project: A project in OpenShift is a container for applications and related resources.

   oc new-project my-app-project

1. Deploy applications using Docker images: You can create a deployment for a Docker image by specifying the image in the deployment configuration.

   oc new-app my-openshift-registry.example.com/my-project/my-app:v1

1. Public application: To access your application externally, expose the service via a route.

   oc expose svc/my-app

1. Extension application: OpenShift lets you easily scale your application up or down.

   oc scale --replicas=3 deployment/my-app

Step 4: Automate the build using OpenShift Pipelines

You can integrate Docker with OpenShift OpenShift pipeline (Tekton based) Automated CI/CD workflow. This allows you to automatically build a Docker image when you commit your code to a Git repository.

1. Create pipeline:

   Define a pipeline that builds a Docker image and pushes it to the OpenShift registry.

2. trigger construction:

   Set up triggers to automatically start the pipeline when new code is committed or merged.

4. Docker and OpenShift security features

OpenShift includes additional security features beyond Docker to enable a more secure containerized environment.

• safety situation: Define security settings for containers running in OpenShift, such as restricting permissions or executing as a specific user.
• Role-based access control (RBAC): Manage access to resources in OpenShift by assigning roles to users.
• Image scanning: OpenShift can automatically scan Docker images for vulnerabilities before deploying them.

5. Benefits of using Docker with OpenShift

• Simplify development and deployment: Docker containers ensure consistency across different environments, and OpenShift uses Kubernetes to handle scaling and orchestration.
• Safety: OpenShift adds enhanced security policies on top of Docker, including image scanning, access control, and secure networking.
• Automated build and continuous integration: OpenShift integrates seamlessly with Docker for building images and setting up automated CI/CD pipelines.
• Enterprise support: OpenShift provides enterprise-grade support, including multi-tenant architecture and integrated monitoring and Docker-based application deployment.

6. Conclusion

Using Docker with OpenShift enables developers to take advantage of the power of Docker containerized applications while benefiting from the additional management, security, and automation features of OpenShift. Whether you use Docker to package applications or OpenShift for orchestration, the combination creates a powerful, secure, and scalable environment for modern application development and deployment.