Environment variables in Compose in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set an environment variable in a Docker Compose service.

Docker

services:
  web:
    image: nginx
    environment:
      - PORT=[1]

Drag options to blanks, or click blank then click option'

A5000

B8080

C3000

D80

Attempts:

3 left

💡 Hint

Common Mistakes

Using a port number that is not standard for HTTP.

Leaving the environment variable value empty.

The environment variable PORT is set to 80, which is the default HTTP port commonly used in web servers.

2fill in blank

medium

Complete the code to use an environment variable from the host system in Docker Compose.

Docker

services:
  app:
    image: myapp
    environment:
      - API_KEY=[1]

Drag options to blanks, or click blank then click option'

A${API_KEY}

BAPI_KEY

C$API_KEY

D$$API_KEY

Attempts:

3 left

💡 Hint

Common Mistakes

Using just $API_KEY without braces.

Using the variable name as a plain string.

In Docker Compose, to use a host environment variable, you wrap it in ${}. So ${API_KEY} injects the host's API_KEY value.

3fill in blank

hard

Fix the error in the environment variable syntax to correctly pass a variable with a default value.

Docker

services:
  db:
    image: postgres
    environment:
      - POSTGRES_PASSWORD=[1]

Drag options to blanks, or click blank then click option'

A${POSTGRES_PASSWORD-defaultpass}

B$POSTGRES_PASSWORD-defaultpass

C${POSTGRES_PASSWORD:-defaultpass}

D$POSTGRES_PASSWORD:-defaultpass

Attempts:

3 left

💡 Hint

Common Mistakes

Missing the colon before the dash.

Using $ without braces for default values.

The correct syntax to provide a default value for an environment variable in Docker Compose is ${VAR:-default}. This means use VAR if set, otherwise use default.

4fill in blank

hard

Fill both blanks to define environment variables using a .env file and override one variable inline.

Docker

services:
  api:
    image: myapi
    env_file:
      - [1]
    environment:
      - DEBUG=[2]

Drag options to blanks, or click blank then click option'

A.env

Bproduction.env

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong filename for the env_file.

Setting DEBUG to a string that is not recognized as boolean.

The env_file key points to the .env file to load variables. The DEBUG variable is overridden inline to false.

5fill in blank

hard

Fill all three blanks to create a service with environment variables from a file, inline variables, and a default fallback.

Docker

services:
  worker:
    image: workerapp
    env_file:
      - [1]
    environment:
      - LOG_LEVEL=[2]
      - RETRY_COUNT=[3]

Drag options to blanks, or click blank then click option'

Aworker.env

B${LOG_LEVEL:-info}

C${RETRY_COUNT:-3}

Ddefault.env

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect env file names.

Not using default value syntax for environment variables.

The env_file points to worker.env. The LOG_LEVEL and RETRY_COUNT variables use default values if not set in the environment.