Volumes for persistent data in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the volume listing command?

You ran the command docker volume ls after creating a volume named mydata. What will the output show?

Docker

docker volume ls

A

VOLUME NAME
mydata

B

DRIVER    VOLUME NAME
local     mydata

C

local     mydata
local     otherdata

D Error: No volumes found

💡 Hint

Remember that docker volume ls shows the driver and volume name columns.

The docker volume ls command lists volumes with two columns: DRIVER and VOLUME NAME. Since you created mydata, it appears under VOLUME NAME with the driver local.

🧠 Conceptual

intermediate

Why use Docker volumes for persistent data?

Which reason best explains why Docker volumes are used for persistent data?

A Volumes allow data to persist even if the container is deleted.

B Volumes make containers run faster by using more CPU.

C Volumes automatically backup data to the cloud.

D Volumes prevent containers from using network resources.

💡 Hint

Think about what happens to data inside a container when the container is removed.

Docker volumes store data outside the container's writable layer, so data remains safe even if the container is deleted or recreated.

❓ Configuration

advanced

Which Docker Compose volume configuration mounts a host directory correctly?

Given this snippet in docker-compose.yml, which option correctly mounts the host directory /home/user/data to the container path /app/data?

Docker

services:
  app:
    image: myapp
    volumes:

A - /app/data:/home/user/data

B - /home/user/data

C - data:/app/data

D - /home/user/data:/app/data

💡 Hint

Remember the format is host_path:container_path.

In Docker Compose, to mount a host directory, you specify the host path first, then the container path separated by a colon.

❓ Troubleshoot

advanced

Why does data not persist after container restart?

You created a container with a volume, but after restarting the container, the data inside /data is missing. What is the most likely cause?

A The volume was not properly mounted to <code>/data</code> in the container.

B The host disk is full, so data cannot be saved.

C The container image deletes data on startup automatically.

D Docker volumes do not support data persistence across restarts.

💡 Hint

Check the volume mount path in the container.

If the volume is not mounted to the correct container path, data written inside the container will not be saved to the volume and will be lost on restart.

🔀 Workflow

expert

Order the steps to create and use a Docker volume for persistent data

Put these steps in the correct order to create a Docker volume and use it in a container.

A 1,3,2,4

B 2,1,3,4

C 1,2,3,4

D 3,1,2,4

💡 Hint

Think about creating the volume before using it in a container.

First, create the volume. Then run the container with the volume mounted. Next, write data inside the container to the volume path. Finally, stop and remove the container but keep the volume for data persistence.