Bind mounts for development in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Bind mount behavior with file changes

You run a Docker container with this command:

docker run -it -v /host/app:/container/app ubuntu bash

If you edit a file inside /host/app on your host machine, what happens inside the container's /container/app directory?

A The container deletes the file automatically when the host file changes.

B The file inside the container does not change until the container is restarted.

C The container creates a copy of the file and changes do not sync back to the host.

D The file inside the container updates immediately to match the host file changes.

💡 Hint

Think about what a bind mount does: it links host and container directories directly.

A bind mount links the host directory to the container directory directly. Any changes on the host are immediately visible inside the container and vice versa.

❓ Configuration

intermediate

Correct bind mount syntax in docker-compose

Which docker-compose service configuration correctly sets a bind mount from the host ./src directory to the container /app directory?

A

volumes:
  - /app:./src

B

volumes:
  - /src:/app

C

volumes:
  - ./src:/app

D

volumes:
  - app:/src

💡 Hint

Remember the format is host_path:container_path.

In docker-compose, bind mounts use the format host_path:container_path. So ./src:/app mounts the local src folder to /app inside the container.

❓ Troubleshoot

advanced

Why are file changes not visible inside container?

You set up a bind mount with:

docker run -v /home/user/project:/app myimage

But when you edit files in /home/user/project on the host, the container does not see the changes. What is the most likely cause?

A The bind mount path on the host is incorrect or does not exist.

B The container's /app directory is read-only and cannot update.

C Docker does not support bind mounts on Linux hosts.

D The container is using a cached image and needs to be rebuilt.

💡 Hint

Check the exact path on your host machine carefully.

If the host path does not exist or is mistyped, Docker creates an empty directory inside the container, so changes on the host won't appear.

🔀 Workflow

advanced

Using bind mounts for live code development

You want to develop a Node.js app inside a Docker container and see code changes immediately without rebuilding the image. Which workflow is best?

A Build the image once, then use a bind mount to link your local code folder to the container's app folder.

B Rebuild the Docker image every time you change code, then restart the container.

C Copy code into the container at runtime using docker cp after each change.

D Use a Docker volume instead of a bind mount for live code syncing.

💡 Hint

Think about how to avoid rebuilding the image for every code change.

Bind mounts let the container use your local code directly, so changes appear immediately without rebuilding or copying files.

✅ Best Practice

expert

Security considerations with bind mounts

Which is the safest practice when using bind mounts in Docker for development?

A Bind mount the entire host root directory to the container for full access.

B Bind mount only the specific project directory needed by the container.

C Avoid using bind mounts and copy files into the container instead.

D Run the container as root user to avoid permission issues with bind mounts.

💡 Hint

Think about limiting access to only what is necessary.

Binding only the needed project directory limits the container's access to host files, reducing security risks.