How to Use Environment Variables in Kubernetes Persistent Volume Claims for Storage Size

Learn how to specify environment variables in Kubernetes persistent volume claims. Discover how to use `envsubst` for dynamic storage size definitions.
---
This video is based on the question https://stackoverflow.com/q/70084003/ asked by the user 'devdanej' ( https://stackoverflow.com/u/15904779/ ) and on the answer https://stackoverflow.com/a/70084308/ provided by the user 'jabbson' ( https://stackoverflow.com/u/4190565/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Specifying environment variable for k8s pvc for storage size

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Specifying Environment Variables for Kubernetes Persistent Volume Claims (PVC)

Kubernetes is a robust platform that enables developers to manage containerized applications easily. One common challenge developers face is configuring persistent storage for applications using Persistent Volume Claims (PVC). In particular, you might wonder whether it's possible to utilize environment variables within PVC YAML definitions, especially for setting storage size. Let’s explore how you can achieve this effectively.

The Challenge: Dynamic Storage Size in PVC

When dealing with Kubernetes, you often need to specify the storage size in your PVC. This becomes particularly useful when you have multiple environments or varying requirements that necessitate dynamic configuration. For example, in a continuous integration pipeline that uses Jenkins, the storage size might need to adjust based on the specific environment, such as development, testing, or production.

Here's a simplified example of how you might typically define a PVC to request a storage size:

[[See Video to Reveal this Text or Code Snippet]]

In this example, the storage size is meant to change dynamically based on the JENKINS_PV_SIZE environment variable. However, Kubernetes does not natively substitute environment variables in YAML definitions. This is where we'll need a workaround.

The Solution: Utilizing envsubst

To achieve variable substitution in your PVC YAML, you can use a command-line utility called envsubst. This tool allows you to substitute environment variables defined in your shell with those present in your environment directly into your Kubernetes manifest files.

Step-by-Step Guide

Set the Environment Variable: First, make sure you've set the environment variable. For example, you can do so in your terminal session:

[[See Video to Reveal this Text or Code Snippet]]

Prepare your YAML File: Have your PVC manifest saved in a file named pvc.yaml, as shown in the earlier example.

Use envsubst Command: Run the envsubst command to replace the ${JENKINS_PV_SIZE} with the actual value, and pipe it into the kubectl apply command:

[[See Video to Reveal this Text or Code Snippet]]

Here, envsubst < pvc.yaml reads your YAML file and substitutes the environment variables, while | kubectl apply -f - directly applies the modified manifest to your Kubernetes cluster.

Tips for Success

Ensure that you are working in a Linux or macOS environment, as envsubst is primarily available in those operating systems.

Always double-check the values of your environment variables to avoid misconfigurations that might lead to storage issues.

Conclusion

Using environment variables within your Kubernetes Persistent Volume Claims can significantly enhance your deployment flexibility. By utilizing the envsubst command, you can dynamically set essential parameters, such as storage size, based on the configurations for different environments. This approach promotes better management and scalability for your applications deployed in Kubernetes.

Now you can confidently customize your PVC configurations with environment variables for a more dynamic and efficient workflow.

Видео How to Use Environment Variables in Kubernetes Persistent Volume Claims for Storage Size канала vlogize