Overview

Kubernetes, k8s, or kube, is an open source platform that automates container operations. It eliminates most of the existing manual processes, which involve the deploying, scaling, and managing of containerized applications.

Components

Kubernetes Master

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• ReplicaSet ensures that a specified number of Pod replicas are running at any given time.
• Deployment is used to change the current state to the desired state.
• StatefulSet is used to ensure control over the deployment ordering and access to volumes, etc.
• DaemonSet is used to run a copy of a Pod on all the nodes of a cluster or on specified nodes.
• Job is used to perform some task and exit after successfully completing their work or after a given period of time.

Defining An Object

apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 2 # tells deployment to run 2 pods matching the template
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80

References

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