KUBERNETES DEPLOYMENT | REPLICA SETS

In Kubernetes (k8s), everything is managed through YAML manifests. These manifests define the desired state of the system, including deployments, replica sets, pods, and containers. Here's an explanation of key concepts and differences:

1. Container vs Pod vs Deployment

• Container ??: A container is the smallest unit in Kubernetes and represents a lightweight, executable software package that includes everything required to run an application (code, libraries, environment, etc.). It runs isolated but shares the OS kernel with other containers. Docker is the most common tool for creating containers.
• Pod ??: A pod is the basic deployable unit in Kubernetes and can contain one or more containers. It represents a single instance of a running process in the cluster. Pods share networking and storage resources, and containers within the same pod can communicate with each other easily. Each pod is assigned a unique IP address.
• Deployment ??: A deployment in Kubernetes manages pods and ensures the desired number of replica sets (and thus pods) are running. It is responsible for rolling out updates, scaling up or down, and implementing auto-healing when a pod crashes. A deployment will automatically create and manage replica sets.

2. Deployment vs Replica Set

• Replica Set ??: A replica set is a controller in Kubernetes responsible for maintaining a stable set of running pods. It ensures that a specified number of pod replicas are running at all times. If a pod crashes or is deleted, the replica set ensures that a new one is created to maintain the desired state.
• Deployment ??: A deployment is a higher-level abstraction over a replica set. When you create a deployment, it automatically creates and manages a replica set. The deployment controller handles rolling updates (replacing old pods with new ones) and rollbacks. The deployment manages the entire lifecycle of an application and ensures its stability.

Key Differences:

• Container: A lightweight executable unit of an application.
• Pod: A group of one or more containers managed together as a unit.
• Deployment: Manages replica sets and ensures that pods meet the desired state.
• Replica Set: Ensures a specified number of pod replicas are running, created by the deployment.

Each of these components plays a crucial role in Kubernetes for ensuring application scalability, availability, and self-healing capabilities.