Running Docker Compose

Docker Compose has two important commands — up and down.

Starting Containers (up)

docker compose -f mongodb.yaml up -d

Explanation

• -f specifies the file name
• up means create and start all containers defined in the file
• -d runs everything in detached mode (in background)

What Happens When We Run This?

When we execute the command:

Docker Compose performs the following steps:

1. Creates a default network automatically
   (example name: test-app-default)
2. Creates all services defined in the YAML file
3. Starts all containers
4. Connects all containers to the same network

Example Containers Started

If our file contains:

• mongo
• mongo-express

Then Docker Compose will:

• Start MongoDB container
• Start Mongo Express container
• Connect both internally using the default network

Important Note

We may see a warning like:

the version attribute is obsolete

This happens in newer versions of Docker Compose.

You can:

• Ignore it, OR
• Remove the version field from the YAML file

Stopping and Removing Containers (down)

Whenever we want to permanently delete all containers defined in the file:

docker compose -f mongodb.yaml down

What Happens When We Run This?

Docker Compose performs cleanup automatically:

1. Stops all running containers defined in the file
2. Removes those containers
3. Removes the automatically created network
4. Cleans up the entire Compose setup

Before vs After

Key Takeaways

• docker compose up -d → Starts the full application stack
• docker compose down → Completely removes the stack
• Docker Compose automatically handles:
  • Networks
  • Container creation
  • Container startup
• One file manages the entire multi-container setup