docker compose up and down - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of docker compose up when the service is already running?

You run docker compose up on a project where the containers are already running. What will happen?

A Docker Compose will attach to the existing containers and show their logs.

B Docker Compose will recreate all containers regardless of their current state.

C Docker Compose will throw an error saying containers are already running.

D Docker Compose will stop the running containers and start new ones.

💡 Hint

Think about how Docker Compose behaves to avoid restarting containers unnecessarily.

When you run docker compose up and containers are already running, Docker Compose attaches to them and streams their logs instead of recreating or stopping them.

💻 Command Output

intermediate

What happens when you run docker compose down?

You have a Docker Compose project running. You execute docker compose down. What is the result?

A It removes only the containers but leaves networks and volumes running.

B It only stops the containers but keeps networks and volumes intact.

C It stops and removes containers and networks created by <code>up</code>.

D It restarts the containers without removing anything.

💡 Hint

Consider what down means compared to stop.

docker compose down stops and removes containers and networks created by up. It cleans up the environment.

🔀 Workflow

advanced

Order the steps to safely update a service using Docker Compose

You want to update a service defined in your Docker Compose file. Put these commands in the correct order to update the service without downtime.

A 3,1,4,2

B 1,2,4,3

C 1,2,4

D 1,2

💡 Hint

Think about updating only the service without stopping the whole project.

To update a service without downtime, first pull the latest image, then rebuild and restart only that service with docker compose up -d --no-deps --build <service_name>. You do not need to bring the whole project down.

❓ Troubleshoot

advanced

Why does docker compose down not remove volumes by default?

You ran docker compose down but noticed your volumes still exist. Why does this happen?

A Volumes are persistent by design and must be removed explicitly with <code>--volumes</code> flag.

B Docker Compose has a bug that prevents volume removal.

C Volumes are removed only if containers are stopped manually before running <code>down</code>.

D Volumes are removed only if you use <code>docker compose stop</code> before <code>down</code>.

💡 Hint

Think about data safety and persistence in Docker volumes.

Docker volumes store data persistently. To avoid accidental data loss, docker compose down does not remove volumes unless you add the --volumes flag explicitly.

✅ Best Practice

expert

Which command sequence is best to completely reset a Docker Compose environment including volumes?

You want to completely reset your Docker Compose environment, removing containers, networks, and volumes. Which command sequence achieves this safely?

A docker compose down --volumes && docker network prune

B docker compose down --rmi all --volumes

C docker compose down && docker volume prune

D docker compose stop && docker compose rm -v && docker network prune

💡 Hint

Consider removing images, volumes, and networks in one command.

docker compose down --rmi all --volumes stops and removes containers, networks, volumes, and images created by the compose project, fully resetting the environment.