Creating and managing volumes in Docker - Practice Exercises

Challenge - 5 Problems

💻 Command Output

intermediate

Volume Creation Command Output

What is the output of the command docker volume create mydata when run on a system with no existing volume named mydata?

Docker

docker volume create mydata

A Error: volume mydata already exists

B Created volume with ID abc123

C mydata

D No output

💡 Hint

The command returns the name of the created volume if successful.

The docker volume create command outputs the name of the newly created volume. If the volume does not exist, it creates it and prints its name.

❓ Troubleshoot

intermediate

Volume Removal Error Diagnosis

You run docker volume rm mydata but get the error: Error: volume is in use - [container_id]. What is the most likely cause?

A The volume is currently attached to a running container.

B The volume does not exist on the system.

C Docker daemon is not running.

D The volume is corrupted and cannot be removed.

💡 Hint

Volumes cannot be removed if they are used by containers.

Docker prevents removal of volumes that are currently used by containers to avoid data loss or container failure.

❓ Configuration

advanced

Docker Compose Volume Configuration

In a docker-compose.yml file, which volume configuration correctly mounts a named volume dbdata to /var/lib/mysql inside the container?

Docker

version: '3.8'
services:
  db:
    image: mysql
    volumes:

A - dbdata:/var/lib/mysql

B - /var/lib/mysql:dbdata

C

- type: bind
  source: dbdata
  target: /var/lib/mysql

D

- type: volume
  source: dbdata
  target: /var/lib/mysql

💡 Hint

Use the long syntax for named volumes with type volume.

Option D uses the correct long syntax for named volumes in Docker Compose, specifying type, source, and target correctly.

🔀 Workflow

advanced

Volume Backup and Restore Workflow

Which sequence of commands correctly backs up a Docker volume named mydata to a tar file and then restores it?

A docker volume export mydata > mydata.tar.gz && docker volume import mydata.tar.gz mydata

B docker run --rm -v mydata:/data -v $(pwd):/backup busybox tar czf /backup/mydata.tar.gz /data && docker run --rm -v mydata:/data -v $(pwd):/backup busybox tar xzf /backup/mydata.tar.gz -C /data

C docker cp mydata:/ /backup/mydata.tar.gz && docker cp /backup/mydata.tar.gz mydata:/

D docker save mydata > mydata.tar.gz && docker load mydata.tar.gz

💡 Hint

Use a temporary container to access volume data for backup and restore.

Option B uses a temporary container with the volume mounted to create and extract a tar archive for backup and restore.

✅ Best Practice

expert

Choosing Volume Types for Persistent Data

Which statement best describes when to use Docker named volumes instead of bind mounts for persistent data?

A Use named volumes when you want Docker to manage the storage location and lifecycle of data independently from the host filesystem.

B Use named volumes only when you need to share data between containers on different hosts.

C Use bind mounts when you want Docker to manage data storage automatically without host interference.

D Use bind mounts to store data inside Docker’s internal volume storage area.

💡 Hint

Think about who controls the data location and lifecycle.

Named volumes are managed by Docker and stored in Docker’s storage area, making them portable and easier to manage than bind mounts which directly map host directories.