What are the recommended approaches for managing multiple environment variables in Docker containers in a sustainable and secure way? For example, keeping variables separate from the codebase, using encrypted storage, or integrating with CI/CD pipelines—what are the community experiences with these methods? What are the advantages and potential disadvantages of these approaches? Which strategies do you prefer for this?
How do you best manage multiple environment variables in Docker containers?
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To manage multiple environment variables cleanly in Docker containers, I usually rely on a combination of **Docker Compose files** (or `docker run --env-file`) and a **secrets management tool** like HashiCorp Vault or AWS Secrets Manager. The variables themselves are stored in a `.env` file, which isn’t committed to the repository, while sensitive data (passwords, tokens) is injected into the container runtime system as encrypted values via the secrets backend. In contrast, Kubernetes already provides native **ConfigMaps** and **Secrets**, which can be mounted directly into pods via declarative YAML—this simplifies orchestration but requires migrating to K8s.
The advantage of the Docker-only approach is its lower complexity and seamless integration into any CI/CD pipeline (Jenkins, GitLab CI, GitHub Actions): one step fetches secrets from Vault, writes them to a temporary `.env` file, and starts the container. The downside is that you have to set up and maintain secrets management yourself, whereas Kubernetes offers it out of the box—though that comes with the added learning curve and overhead of managing a K8s cluster.
In my current setup, I use Docker Compose for local development, paired with Vault for production secrets, while letting the CI system dynamically generate the `.env` file. This keeps everything separate from the code, encrypted, and easy to scale.