1. What is Docker? Docker is a platform for developing, shipping, and running applications inside containers. Containers package an application and its dependencies together, ensuring that it runs seamlessly in any environment, from development to production.
2. Key Concepts:
- Containers: Lightweight, standalone, and executable packages that include everything needed to run a piece of software, including code, runtime, libraries, and system settings.
- Images: Read-only templates used to create containers. An image includes the application and its dependencies.
- Dockerfile: A text file containing a series of commands and instructions to build a Docker image.
- Docker Hub: A cloud-based repository where Docker users can store and share Docker images.
3. Basic Commands:
- docker build: Builds a Docker image from a Dockerfile.
- docker pull: Downloads an image from a Docker registry.
- docker run: Creates and starts a new container from an image.
- docker ps: Lists all running containers.
- docker stop: Stops a running container.
- docker rm: Removes a stopped container.
- docker rmi: Removes an image.
4. Benefits of Docker:
- Portability: Consistent environments across different stages of development.
- Efficiency: Containers share the host OS kernel, which makes them more lightweight than virtual machines.
- Scalability: Easier to scale applications and manage workloads.
Fundamentals of Kubernetes
1. What is Kubernetes? Kubernetes, often abbreviated as K8s, is an open-source platform designed to automate deploying, scaling, and operating application containers. It orchestrates containers to ensure high availability and scalability.
2. Key Concepts:
- Cluster: A set of nodes (physical or virtual machines) running containerized applications.
- Node: A single machine within the cluster.
- Pod: The smallest deployable unit in Kubernetes, a pod can contain one or more containers.
- Service: An abstraction that defines a logical set of pods and a policy to access them.
- Deployment: A higher-level abstraction for managing pods, including scaling and updating applications.
- Namespace: A way to divide cluster resources between multiple users.
3. Basic Commands:
- kubectl create: Creates a resource from a file or stdin.
- kubectl get: Lists resources.
- kubectl describe: Shows detailed information about a resource.
- kubectl delete: Deletes resources by file or stdin.
- kubectl apply: Applies a configuration to a resource by file or stdin.
4. Benefits of Kubernetes:
- Scalability: Easily scale applications up and down based on demand.
- Self-healing: Automatically restarts, replaces, or reschedules containers that fail or are unresponsive.
- Load Balancing: Distributes network traffic evenly to ensure that no single application instance is overwhelmed.
- Automated Rollouts and Rollbacks: Manage deployments with automated updates and rollbacks.
- Resource Management: Efficiently allocate resources and manage workload.
Integration of Docker and Kubernetes:
- Container Runtime: Kubernetes uses Docker as its default container runtime to manage containerized applications.
- Image Management: Kubernetes pulls Docker images from container registries to run containers in pods.
- Orchestration: Kubernetes handles the orchestration of Docker containers, providing advanced features like scaling, self-healing, and service discovery.
Summary
Docker and Kubernetes together form a powerful combination for modern application development and deployment. Docker provides the containerization technology to package and distribute applications, while Kubernetes provides the orchestration and management capabilities to run these applications at scale in a reliable and automated way.
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