# Daily Hack #day61 - docker run --env-file

The `docker run --env-file` command is a useful feature in Docker that allows users to specify environment variables for a container using a file. This command enhances manageability and security by enabling the storage of environment variables in a separate file, rather than directly in the command line or Dockerfile.

### Usage:

To use this command, create a plain text file where each line contains an environment variable in the format `KEY=VALUE`. For example:

```plaintext
DATABASE_USER=root
DATABASE_PASSWORD=secret
API_KEY=123456
```

You can then run a Docker container using these environment variables with the following command:

```sh
docker run --env-file /path/to/envfile myimage
```

### Benefits:

* **Simplicity**: Easily manage multiple environment variables in a single file.
    
* **Security**: Avoid exposing sensitive information like passwords or API keys in shell history or command logs.
    
* **Portability**: Share environment configuration across different environments (development, staging, production) by maintaining different `.env` files.
    

### Example:

```sh
docker run --env-file ./myenv.list ubuntu bash -c "echo $DATABASE_USER"
```

This command will run an Ubuntu container and print the value of `DATABASE_USER` specified in the `myenv.list` file.

Using `--env-file` is an effective practice for organizing and maintaining environment variables for your Docker containers, especially in complex deployment scenarios.

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