Terraform, a widely-used Infrastructure as Code (IaC) tool, simplifies the management and provisioning of infrastructure across various cloud providers. When working with Kubernetes, one essential component Terraform helps to manage is the `ConfigMap`. The `kubernetes_config_map` resource in Terraform allows for the management of Kubernetes ConfigMaps, which are key/value pairs used to configure applications inside Kubernetes clusters. One particularly useful feature of the `kubernetes_config_map` resource is the ability to create a ConfigMap from an `env-file`. This article explores the usage and details of the `--from-env-file` option in Terraform's Kubernetes provider.

Kubernetes ConfigMap and Terraform

A ConfigMap is an API object used to store non-confidential data in key-value pairs. Applications within a Kubernetes cluster can consume these key-value pairs as environment variables, command-line arguments, or as configuration files in a volume. Terraform, through its Kubernetes provider, facilitates the automated creation and management of these ConfigMaps, ensuring consistent environments across deployments.

`--from-env-file` Feature

What is `--from-env-file`?

The `--from-env-file` feature is a Terraform attribute that allows users to create a Kubernetes ConfigMap from a file formatted as an environment file. An environment file is straightforward; it lists environment variables in the form of `KEY=VALUE` pairs. By utilizing this feature, users can transform an existing `.env` file into a Kubernetes ConfigMap resource.

Benefits

• Efficiency: Quickly convert existing environment files into ConfigMaps without manually specifying each key-value pair in Terraform.
• Consistency: Ensures that configurations remain consistent with the environment files already in use, minimizing the risk of errors or mismatches.
• Automation: Seamless integration into CI/CD pipelines that already make use of environment files, facilitating automated deployments.

Creating a `kubernetes_config_map` from an Environment File

Prerequisites

• Terraform: Ensure you have Terraform installed and configured.
• Kubernetes Cluster: Have access to a Kubernetes cluster.
• Kubernetes Provider: Configure the Kubernetes provider in your Terraform settings.

Sample `.env` File

Consider the following `.env` file named `config.env`:

• Provider Configuration: The Kubernetes provider is configured to use the local kubeconfig file.
• Resource Definition: A `kubernetes_config_map` resource is defined with metadata specifying its name and namespace.
• Data Source: The `data_from_file` block reads from the `config.env` file, converting each line into a key-value pair within the ConfigMap.