Docker Compose with Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Nginx container port exposure

You run a Docker Compose setup with Nginx service exposing port 80. What is the output of docker-compose ps regarding the ports column?

Nginx

version: '3.8'
services:
  web:
    image: nginx:latest
    ports:
      - "8080:80"

A web_1 nginx:latest Up 80/tcp

B web_1 nginx:latest Up 0.0.0.0:80->8080/tcp

C web_1 nginx:latest Up 0.0.0.0:8080->80/tcp

D web_1 nginx:latest Up 8080/tcp

💡 Hint

Remember the format is host_port:container_port

The ports mapping in Docker Compose maps host port 8080 to container port 80, so the output shows 0.0.0.0:8080->80/tcp.

❓ Configuration

intermediate

Correct Nginx service restart policy in Docker Compose

Which restart policy ensures the Nginx container restarts automatically only if it crashes, but not if stopped manually?

A restart: always

B restart: on-failure

C restart: no

D restart: unless-stopped

💡 Hint

Think about restart only on crashes, not manual stops.

The 'on-failure' policy restarts the container only if it exits with a failure code, not if stopped manually.

❓ Troubleshoot

advanced

Nginx container fails to start due to port conflict

You have this Docker Compose snippet for Nginx:

ports:
  - "80:80"

But the container fails to start with an error about port 80. What is the most likely cause?

A The container's internal port 80 is blocked by firewall

B The container image is missing the Nginx binary

C Docker Compose file version is incompatible

D Another process on the host is already using port 80

💡 Hint

Check what else might be using port 80 on your computer.

If host port 80 is already in use by another process, Docker cannot bind it for the container, causing startup failure.

🔀 Workflow

advanced

Order of commands to update Nginx container with new config

You updated the Nginx config file on your host. Which sequence of commands correctly applies the changes to the running container using Docker Compose?

A 3

B 4,1,2

C 1,4,2

D 2,3

💡 Hint

You only changed config, not the image.

Restarting the container reloads the config without rebuilding or stopping the whole stack.

✅ Best Practice

expert

Best way to persist Nginx logs in Docker Compose

You want to keep Nginx logs on the host machine so they are not lost when the container is removed. Which Docker Compose volume configuration is best?

A

volumes:
  - ./logs:/var/log/nginx

B

volumes:
  - logs:/var/log/nginx
volumes:
  logs: {}

C

volumes:
  - /var/log/nginx

D

volumes:
  - /var/log/nginx:/var/log/nginx

💡 Hint

Map a host folder to container log folder.

Mapping a host folder (like ./logs) to /var/log/nginx in the container keeps logs on the host persistently.