Why data persistence matters in Docker - See It in Action

Why Data Persistence Matters with Docker

📖 Scenario: Imagine you are running a simple web application inside a Docker container. You want to save user data so it is not lost when the container stops or is removed.

🎯 Goal: Learn how to create a Docker container with a volume to keep data persistent even after the container is deleted.

📋 What You'll Learn

Create a Docker volume named user_data

Run a Docker container named my_app using the busybox image

Mount the user_data volume to /data inside the container

Write a file inside the container's /data directory

Verify the file persists after container removal

💡 Why This Matters

🌍 Real World

Data persistence is critical for applications like databases, web servers, and any service that needs to keep user data safe even if containers restart or are deleted.

💼 Career

Understanding Docker volumes and data persistence is essential for DevOps roles to manage containerized applications reliably in production environments.

1

Create a Docker volume

Create a Docker volume called user_data to store data persistently outside containers.

Docker

# Create the Docker volume user_data
# Your code here

Need a hint?

Use the docker volume create command followed by the volume name.

2

Run a container with the volume mounted

Run a Docker container named my_app using the busybox image. Mount the user_data volume to the container's /data directory.

Docker

docker volume create user_data
# Run the container my_app with user_data volume mounted at /data
# Your code here

Need a hint?

Use docker run -dit --name my_app -v user_data:/data busybox to start the container.

3

Write data inside the container

Use docker exec to write the text Hello, persistent world! into a file named /data/message.txt inside the my_app container.

Docker

docker volume create user_data
docker run -dit --name my_app -v user_data:/data busybox
# Write the message to /data/message.txt inside my_app
# Your code here

Need a hint?

Use docker exec my_app sh -c "echo 'Hello, persistent world!' > /data/message.txt" to write the file.

4

Verify data persistence after container removal

Stop and remove the my_app container. Then run a new container named my_app2 with the same user_data volume mounted at /data. Use docker exec to display the contents of /data/message.txt inside my_app2.

Docker

docker volume create user_data
docker run -dit --name my_app -v user_data:/data busybox
docker exec my_app sh -c "echo 'Hello, persistent world!' > /data/message.txt"
# Stop and remove my_app, then run my_app2 with the same volume
# Display the contents of /data/message.txt inside my_app2
# Your code here

Need a hint?

Use docker stop my_app and docker rm my_app to remove the first container. Then run docker run -dit --name my_app2 -v user_data:/data busybox and docker exec my_app2 cat /data/message.txt to verify the file content.