Environment Variables in DeployStack

DeployStack supports environment variables for your Docker configurations through the .deploystack/env file. This allows you to manage configuration values separately from your Docker files and maintain consistency across deployments.

Adding Environment Variables

Create an env file in your .deploystack directory:

your-repository/
├── .deploystack/
│   ├── env
└── README.md

Your env file should follow the standard environment file format:

# .deploystack/env
DB_USERNAME=myuser
DB_PASSWORD=mysecretpassword
DB_DATABASE=mydatabase

Using Environment Variables

In Docker Compose

Reference environment variables in your docker-compose.yml using the ${VARIABLE_NAME} syntax:

services:
  db:
    image: mariadb:11.2
    environment:
      MYSQL_ROOT_PASSWORD: ${DB_PASSWORD}
      MYSQL_USER: ${DB_USERNAME}
      MYSQL_DATABASE: ${DB_DATABASE}

In Docker Run Commands

For docker-run.txt, use the same variable syntax:

docker run -d \
  -e MYSQL_ROOT_PASSWORD=${DB_PASSWORD} \
  -e MYSQL_USER=${DB_USERNAME} \
  -e MYSQL_DATABASE=${DB_DATABASE} \
  mariadb:11.2

Default Values

DeployStack supports Docker's default value syntax for environment variables. This provides fallback values when variables are not defined.

Syntax

Use ${VARIABLE:-default} where:

• VARIABLE is your environment variable name
• default is the fallback value

Examples

# docker-compose.yml
services:
  web:
    image: nginx:alpine
    environment:
      PORT: ${PORT:-8080}
      NODE_ENV: ${NODE_ENV:-development}

# docker-run.txt
docker run -d \
  -e PORT=${PORT:-8080} \
  -e NODE_ENV=${NODE_ENV:-development} \
  nginx:alpine

Environment Variable Processing

When DeployStack processes your repository:

1. Variables defined in .deploystack/env are read
2. These values replace matching ${VARIABLE} placeholders
3. For undefined variables:
   • If a default value is specified (${VARIABLE:-default}), it's used
   • Otherwise, an empty string is used

Important Notes

• The env file is optional
• Keep sensitive information out of version control
• Variable names are case-sensitive
• Default values provide fallbacks but don't expose sensitive data
• Environment variables in your Docker configuration must use the ${VARIABLE} syntax

Limitations

• Basic environment variable substitution only
• No variable expansion or shell-style manipulation
• Cannot reference other variables within values
• No built-in encryption for sensitive values