Skip to main content

Basics

1. Introduction to Kubernetes Objects​

Kubernetes objects are persistent entities in the Kubernetes system. They represent the state of your cluster and applications running on it. Understanding these objects is key to working effectively with Kubernetes.

2. Understanding YAML in Kubernetes​

  • What is YAML?: YAML, which stands for “YAML Ain't Markup Language,” is a human-readable data serialization standard that can be used in conjunction with all programming languages and is often used to write configuration files.
  • YAML in Kubernetes: Kubernetes uses YAML as a format for specifying the configuration of objects within the cluster. It's preferred due to its readability and ease of use.

3. Pods​

  • Definition: The smallest deployable units created and managed by Kubernetes.
  • Example YAML: 
    apiVersion: v1
    kind: Pod
    metadata:
      name: my-pod
    spec:
      containers:
      - name: my-container
        image: nginx

4. Deployments and ReplicaSets​

  • Definition: Deployments manage the creation and scaling of ReplicaSets.
  • Example YAML: 
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: my-deployment
    spec:
      replicas: 3
      selector:
        matchLabels:
          app: my-app
      template:
        metadata:
          labels:
            app: my-app
        spec:
          containers:
          - name: nginx-container
            image: nginx

5. Services​

  • Definition: Expose an application running on a set of Pods as a network service.
  • Example YAML: 
    apiVersion: v1
    kind: Service
    metadata:
      name: my-service
    spec:
      selector:
        app: my-app
      ports:
        - protocol: TCP
          port: 80
          targetPort: 9376

6. Ingress​

  • Definition: Manages external access to the services in a cluster.
  • Example YAML: 
    apiVersion: networking.k8s.io/v1
    kind: Ingress
    metadata:
      name: example-ingress
    spec:
      rules:
      - host: www.example.com
        http:
          paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-service
                port:
                  number: 80

7. Volumes​

  • Definition: Directory containing data, accessible to containers in a Pod.
  • Example YAML: 
    apiVersion: v1
    kind: Pod
    metadata:
      name: my-pod
    spec:
      containers:
      - name: my-container
        image: nginx
        volumeMounts:
        - mountPath: /usr/share/nginx/html
          name: my-volume
      volumes:
      - name: my-volume
        hostPath:
          path: /data
          type: Directory

8. Namespaces​

  • Definition: Virtual clusters backed by the same physical cluster.
  • Example YAML: 
    apiVersion: v1
    kind: Namespace
    metadata:
      name: my-namespace