Augustine's Notes

Deployments

2 min read

Deployments

Source: https://notes.kodekloud.com/docs/CKA-Certification-Course-Certified-Kubernetes-Administrator/Core-Concepts/Deployments/page

Summary: This guide explores Kubernetes deployments, simplifying application management with features like rolling updates, rollbacks, and high availability.

Key Notes

  • Hello and welcome! My name is Mumshad Mannambeth. In this guide, we dive into Kubernetes deployments—an abstraction that simplifies managing your applications in a production environment. Rather than interacting directly with pods and ReplicaSets, deployments offer advanced features that enable you to:
  • Deploy multiple instances of your application (like a web server) to ensure high availability and load balancing.
  • Seamlessly perform rolling updates for Docker images so that instances update gradually, reducing downtime.
  • Quickly roll back to a previous version if an upgrade fails unexpectedly.
  • Pause and resume deployments, allowing you to implement coordinated changes such as scaling, version updates, or resource modifications.
  • Previously, we discussed how individual pods encapsulate containers and how ReplicaSets maintain multiple pod copies. A deployment, however, sits at a higher level, automatically managing ReplicaSets and pods while providing enhanced features like rolling updates and rollbacks.
  • Creating a Deployment
  • To create a deployment, start by writing a deployment definition file. This file is similar to a ReplicaSet definition, with the key difference being that the kind is set to Deployment instead of ReplicaSet. Below is an example of a correct deployment definition file:
  • apps/v1
  • Once your deployment definition file (for example, named deployment-definition.yml) is ready, create the deployment with the following command:
  • deployment-definition.yml
  • The command output should confirm that the deployment has been created:
  • deployment “myapp-deployment” created
  • To verify the deployment, run:
  • The output will look similar to this:
  • NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
  • myapp-deployment 3 3 3 3 21s
  • Behind the Scenes: How Deployments Work
  • When you create a deployment, Kubernetes automatically creates an associated ReplicaSet. To see this in action, run:
  • You’ll notice a new ReplicaSet with a name derived from your deployment. This ReplicaSet oversees the creation and management of pods. To view the pods managed by the ReplicaSet, run:
  • While deployments and ReplicaSets work together seamlessly, deployments provide additional functionalities such as rolling updates, rollbacks, and the ability to pause/resume changes.
  • To view all the created Kubernetes objects—deployments, ReplicaSets, pods, and more—use the following command:
  • This gives you a comprehensive overview of your deployment’s components.
  • A sample output of the “kubectl get all” command might be:

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