Practical Example of Docker Volumes

Let's see a small practical example of how Docker volumes work. We will run a small Ubuntu container:

docker run -it -v /Users/your-username/Desktop/data:/test/data ubuntu

Explanation

-v is the volume flag
/Users/your-username/Desktop/data is the host machine path (our local machine's folder)
/test/data is the container path (where it gets mounted inside the container)

What This Means

This creates a mapping (bind mount) between:

• Host machine folder → /Users/your-username/Desktop/data
• Container folder → /test/data

So whatever data is stored inside the container at /test/data is also reflected on the host machine.

Testing the Volume

Inside the container, create two files:

cd /test/data

touch index.html
touch server.js

What Happens Next?

Now check your host machine (Desktop folder):

/Desktop/data

You will see:

• index.html
• server.js

Even though these files were created inside the container, they are now visible on the host machine as well.

Persistence Test

Step 1 — Exit Container

exit

Step 2 — Restart Container

Start the container again:

docker run -it -v /Users/your-username/Desktop/data:/test/data ubuntu

You will still see the same files inside /test/data.

Step 3 — Delete Container

Even if we completely delete the container:

docker rm <container-id>

Final Result

Check the host machine folder:

/Desktop/data

The files are still present:

• index.html
• server.js

Key Observation

Even after:

• Stopping the container
• Restarting the container
• Deleting the container

The data still persists on the host system.

Why This Works

Because Docker volumes (bind mounts in this case) store data outside the container filesystem.

So:

Container data → mapped to → Host machine directory

Summary

• -v flag is used to create a volume (bind mount)
• Host directory is mapped to a container directory
• Data is shared between host and container
• Data persists even after container deletion
• This is essential for persistent storage in Docker