Thursday, April 28, 2022

Kubernetes # helm

What is Helm?

  • Helm is considered a package manager for Kubernetes.
  • Helm automates the maintenance of the YAML manifest file for the Kubernetes object.
  • Helm keeps track of the version history of every chart installation.
  • It helps developers and operators to package, configure and deploy applications and services onto the Kubernetes cluster easily.
  • We can deploy versions of the chart.


Why do we need Helm?

  • At some point, writing a manifest YAML file for any application in Kubernetes would result in complexity since that application would have a config YAML file, pod YAML file, service YAML file, and many more.
  • Helm helps us in managing these tedious time-consuming tasks by allowing us to create charts where we define the Kubernetes objects as packages.
  • In short, every Kubernetes object would need a separate YAML file and if we want to make any changes or upgrade our applications we would result up opening each manifest file and making those changes which is a time-consuming task.


What are Helm charts?

  • A Helm chart can be considered an instruction manual. 

  • Charts can be considered as a collection of files.
  • Concept of Helm chart:

    1. Charts: Template of Kubernetes resources. 
    2. Release: A chart deployed to a Kubernetes cluster.
    3. Repository: Storage for Helm chart.

Difference between Helm2 and Helm3?

Helm 2:

  • An extra component (Tiller) was installed in the Kubernetes cluster while using helm2.
  • Any action to be performed by the helm, it had to communicate with Tiller and that would communicate with the Kubernetes cluster.
  • Rollback to older change: Helm2 compares the current revision(chart) with the previous version(chart) and if the current revision is a manual change, helm2 won't find any revision and its lacks in rollback to older changes.

Helm 3:

  • Any user who had tiller access, could perform any action in cluster, which lead to security concerns hence it was removed.
  • Roll back to older change: Helm3 uses 3-way strategic merge patch to get the changes and revert back.

Folder Structure:

  •  Chart.yaml - All the information about the chart that we are packaging will be added to chart.yaml file
  • values.yaml - These files are like the input files where configurable values are stored..helmignore: This is similar to .gitignore file that we use in git.
  • Templates: Here we place our manifest files such as deployment.yaml, service.yaml,config.yaml.
  • Charts: Here we store other charts.

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