Named volumes for data sharing in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of Docker volume creation command

What is the output when you run the command to create a named volume called mydata?

Docker

docker volume create mydata

A Created volume with ID abc123

B Volume mydata created

C Error: volume name required

D mydata

💡 Hint

The command returns the volume name if successful.

The docker volume create command returns the name of the created volume, which is mydata in this case.

🧠 Conceptual

intermediate

Purpose of named volumes in Docker

Which option best describes the main purpose of using named volumes in Docker?

A To speed up container startup time by caching images

B To share data between containers and persist data beyond container life

C To isolate network traffic between containers

D To limit CPU usage of containers

💡 Hint

Think about data persistence and sharing.

Named volumes allow containers to share data and keep it even if containers are removed, unlike anonymous or bind mounts.

❓ Configuration

advanced

Correct Docker Compose volume syntax

Which Docker Compose snippet correctly defines a named volume shared_data and mounts it to /app/data inside the container?

A

volumes:
  shared_data:
services:
  app:
    volumes:
      - /app/data:shared_data

B

volumes:
  - shared_data:/app/data
volumes:
  shared_data:

C

services:
  app:
    volumes:
      - shared_data:/app/data
volumes:
  shared_data:

D

services:
  app:
    volumes:
      - /app/data:shared_data
volumes:
  shared_data:

💡 Hint

Remember the order is volume_name:container_path and volumes must be declared at root.

Option C correctly declares the named volume under volumes and mounts it inside the service under volumes with the syntax shared_data:/app/data.

❓ Troubleshoot

advanced

Troubleshooting volume data persistence issue

A developer notices that data written inside a container to a named volume is lost after the container is removed and recreated. What is the most likely cause?

A The container was started without mounting the named volume

B The volume was not declared in the Docker Compose file under <code>volumes</code>

C The volume was mounted as a bind mount to a host directory

D The container was run with <code>--rm</code> flag

💡 Hint

Check if the volume is actually connected to the container.

If the container does not mount the named volume, data is stored inside the container's writable layer and lost when the container is removed.

🔀 Workflow

expert

Order of commands to share data using named volumes

Arrange the steps in the correct order to share data between two containers using a named volume.

A 1,2,3,4

B 2,1,3,4

C 1,3,2,4

D 1,2,4,3

💡 Hint

You must create the volume before using it in containers.

First create the volume, then start the first container mounting it, write data, and finally start the second container mounting the same volume to share data.