docker-compose.yml structure - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the version key in a docker-compose.yml file?

The version key specifies the Compose file format version. It tells Docker Compose which syntax rules to follow when reading the file.

beginner

What does the services section define in a docker-compose.yml file?

The services section lists all the containers (services) that Docker Compose will create and manage. Each service has its own configuration like image, ports, and environment variables.

intermediate

In docker-compose.yml, what is the role of the volumes key under a service?

The volumes key connects storage from the host machine or named volumes to the container, allowing data to persist or be shared between containers.

beginner

How do you specify which ports to expose from a container in docker-compose.yml?

Use the ports key under a service. It maps host ports to container ports in the format host_port:container_port.

beginner

What is the purpose of the environment section in a docker-compose.yml service?

The environment section sets environment variables inside the container. These variables can configure the app or service running inside.

Which key in docker-compose.yml defines the containers to run?

A volumes

B networks

C services

D images

The services key lists all containers Docker Compose will create.

How do you map port 8080 on your computer to port 80 in the container?

A ports: - "8080:80"

B ports: - "80"

C ports: - "8080"

D ports: - "80:8080"

The format is host_port:container_port, so 8080:80 maps host port 8080 to container port 80.

What does the volumes key do in a service definition?

A Sets environment variables

B Connects storage between host and container

C Defines network settings

D Specifies container image

Volumes connect storage from the host or named volumes to containers for data persistence.

Where do you specify environment variables for a container in docker-compose.yml?

A under <code>environment</code> key

B under <code>ports</code> key

C under <code>volumes</code> key

D under <code>networks</code> key

The environment key sets environment variables inside the container.

What is the correct file format for docker-compose.yml?

A JSON

B XML

C INI

D YAML

docker-compose.yml uses YAML format, which is easy to read and write.

Describe the main sections of a docker-compose.yml file and their purposes.

Think about what each part controls in running containers.

Explain how you would expose a web app running on port 80 inside a container to port 3000 on your computer using docker-compose.yml.

Remember the format is host_port:container_port.