preparing custom script extension in Azure devops

Question

What is the custom script extension and why we use?

Where should I start to start preparing custom scripts extention? and how it is useful.

What is the process to prepare custom scripts extention?

Answer 1

Hello Diptesh,

Welcome to Q&A, I will try to answer your question one by one:

What’s a custom script extension?

Think of it like a handy tool that runs your scripts on Azure virtual machines (VMs). Whether you’re installing software, setting up configurations, or automating post-deployment stuff, it’s your go-to for saving time and avoiding manual hassle.

Why use it?

Custom script extensions are useful for automating repetitive tasks, such as configuring systems, applying software patches, or setting up virtual machines (VMs) consistently.

Where should you start?

First, set up your environment. Install tools like Node.js, grab Visual Studio Code, and set up the Azure DevOps Extension SDK. Then, get comfy with Azure DevOps pipelines and the structure of extensions (those task.json and vss-extension.json files are important). Finally, decide where you’ll host your scripts Azure Blob Storage, GitHub, or wherever works for you.

How do you actually make one?

Creating a custom script extension involves several steps, such as setting up your project, writing and testing your script, and packaging it for Azure DevOps. For detailed guidance on these steps, you can refer to the following resources:

• Adding build or release tasks in an extension explains how to create tasks for Azure DevOps extensions. (https://learn.microsoft.com/en-us/azure/devops/extend/develop/add-build-task?view=azure-devops)
• Guide to creating Azure DevOps extensions provides a comprehensive walkthrough for building extensions. (https://cornehoskam.com/posts/creating-an-azure-devops-extension)
• Azure Custom Script Extension for Windows offers insight into the use of custom script extensions for virtual machines. (https://learn.microsoft.com/en-us/azure/virtual-machines/extensions/custom-script-windows)

References:

• https://learn.microsoft.com/en-us/azure/virtual-machines/extensions/custom-script-windows
• https://learn.microsoft.com/en-us/azure/devops/extend/develop/add-build-task?view=azure-devops

If the information helped address your question, please Accept the answer.

Luis

Answer 2

Hi @Shyam Kumar ,

What is a Custom Script Extension?

A custom script extension is a feature in Azure that lets you run scripts (PowerShell, Bash, etc.) on Azure Virtual Machines (VMs) during or after deployment. Think of it like a post it notes for automation, it helps you set up your environment without having to log in and manually configure everything.

For example, you can:

• Install software or dependencies on the VM
• Configure settings or environment variables
• Download and run scripts from a storage location (like Azure Blob, GitHub, etc.)
• Automate fixes or security patches

It’s widely used in Infrastructure as Code setups where consistency and automation are key.

Why is it useful?

In a nutshell - automation, consistency, and speed.

• Avoids manual configuration every time you create a VM
• Ensures environments are set up identically every time (great for Dev/Test/Prod)
• Helps integrate custom configurations into automated Azure DevOps pipelines
• Simplifies complex setups like installing IIS, setting up agents, or applying configs

It’s especially handy in enterprise-scale or DevOps-driven environments.

Where should I start?

If your goal is to integrate custom script execution into Azure DevOps pipelines, then you’re looking at creating a custom build/release task extension in Azure DevOps.

Here’s a good starting roadmap:

Understand the Scope

Decide whether your extension is:

• Target Azure VMs (via Azure Custom Script Extension)
• Or enhancing DevOps Pipelines (via Azure DevOps Task Extension)

Set Up Your Development Environment

• Install Node.js
• Install Visual Studio Code
• Install the Azure DevOps Extension SDK: npm install -g tfx-cli

Structure Your Extension Project You’ll need:

• task.json defines your task inputs, execution method, etc.
• vss-extension.json defines metadata for your DevOps extension

Write and Test Your Script

This can be any script that gets run on a VM or inside a pipeline. Store it securely typically in:

• Azure Blob Storage, GitHub repo, Azure Repos.

Package and Publish Your Extension

• Use tfx-cli to package your extension
• Upload to your Azure DevOps Organization or publish to the Marketplace

How is it Useful in DevOps?

Let’s say you’re deploying a VM and want to install an app, configure IIS, or register a monitoring agent all without manual effort. You can write a script for that and execute it via a custom script extension.

Or in Azure DevOps, you want a reusable task in your pipeline that runs a script across environments. You create a custom task extension that wraps your script logic in a friendly UI with inputs.

Please refer this link for deeper learning Custom Build/Release Task in Azure DevOps, Custom Script Extension for Windows.

Hope it helps!

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