Interactive Shell Using Docker Compose

TLDR

To start an interactive shell in a Docker Compose service, use the docker-compose exec command. This allows you to debug and interact with running containers.

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Docker Compose simplifies the management of multi-container applications. Sometimes, you need to access a running container to debug or interact with it. This guide explains how to start an interactive shell in a Docker Compose service.

Step 1: Define Your Services

Ensure your docker-compose.yml file defines the services you want to run.

Example docker-compose.yml

version: '3.8'
services:
  app:
    image: node:18
    working_dir: /app
    volumes:
      - .:/app
    command: npm start
  db:
    image: postgres:15
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password

Explanation

• app: Defines a Node.js application service.
• db: Defines a PostgreSQL database service.
• volumes: Mounts the current directory into the container.
• environment: Sets environment variables for the database.

Step 2: Start the Services

Start the services using the docker-compose up command.

Command

docker-compose up -d

Explanation

• -d: Runs the services in detached mode.

Step 3: Access an Interactive Shell

Use the docker-compose exec command to start an interactive shell in a running service.

Command

docker-compose exec app sh

Explanation

• exec: Executes a command in a running container.
• app: Specifies the service name.
• sh: Starts a shell session.

Step 4: Debug and Interact

Once inside the container, you can run commands, inspect files, and debug your application.

Example

ls
cat app.js
npm install

Explanation

• ls: Lists files in the current directory.
• cat app.js: Displays the contents of app.js.
• npm install: Installs dependencies.

Best Practices

• Use Descriptive Service Names: Make it easy to identify services.
• Limit Access: Avoid running commands in production containers unless necessary.
• Automate Debugging: Use scripts to automate common debugging tasks.

By following these steps, you can effectively use Docker Compose to start an interactive shell, making debugging and development more efficient.