How to Configure Environment Variables in .npmrc with Google Cloud Build

Learn how to set environment variables in your `.npmrc` file via Google Cloud Build using Docker. This guide provides a step-by-step approach for managing secrets and configuration.
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How to Configure Environment Variables in .npmrc with Google Cloud Build

When working with Google Cloud Build, developers often face challenges when it comes to managing environment variables, especially for sensitive information like authentication tokens in their configurations. Recently, a common problem arose where a user was unable to have the $token variable populate properly in their .npmrc file despite successfully pulling the value from Google Secret Manager. This guide will address this issue and provide a structured solution.

The Problem

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Despite having the right token available, the .npmrc file did not seem to recognize it, leading to confusion and frustration for the developer.

Understanding the Issue

The key factor contributing to this problem is how Docker handles files and environment variables. Simply copying a file (like .npmrc) into the Docker container does not automatically perform variable substitution; environment variables won’t be replaced unless explicitly managed.

Why the Variables Aren't Replaced

File Copying: When you copy a file into a Docker container, it retains its original content, meaning that environment variables inside the file remain unchanged.

Shell Evaluation: If variable substitution happened automatically on every file copy, it could lead to unexpected behavior and make maintaining scripts difficult.

The Solution

We can solve this problem by modifying the Dockerfile to handle the environment variable substitution explicitly. Here’s how to revise it:

Updated Dockerfile

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Breakdown of Changes

Variable Declaration:

Use ENV token=$token to declare the token variable within the Docker container context after pulling it from the Google Secret Manager.

Copy and Transform:

Environment Substitution:

Verify the Output:

By adding cat .npmrc, you can verify that the token substitution occurred as expected, providing assurance that your setup is correct.

Conclusion

Utilizing environment variables in Docker can sometimes be tricky, especially when dealing with sensitive information like tokens. By clearly understanding how Docker manages files and by implementing environment variable substitution correctly, we can solve these issues efficiently. Now you should be able to configure your .npmrc to correctly utilize tokens from Google Secret Manager, making your development process smoother and more secure.

By following this guide, you can effectively handle environment variables within your Docker context, ensuring that sensitive data is managed securely and correctly.