Docker Volumes – Explained Clearly with Practical Examples

Let's understand Docker Volumes using a simple real-world example and then implement it step by step.

1. First, understand the problem

Imagine you have created a simple ASP.NET Core Web API application and deployed it inside a Docker container.

Your application creates a file called message.txt.

Initially, the file contains:

Hello from Docker Container!

Now, let's say you stop and delete the container.

What happens to message.txt?

The file will also be deleted because it was stored inside the container's writable filesystem.

This is the main problem Docker Volumes solve.

2. What is a Docker Volume?

A Docker Volume is a storage mechanism that allows us to store data outside the container's lifecycle.

Even if you stop, delete, or recreate a container, the data stored in the volume remains available.

Think of it like this:

• Container = Temporary computer.

• Volume = Permanent hard disk.

• Application = Program running inside the computer.

Without Docker Volume

Docker Host
    |
    +---- Container
             |
             +---- Application
             |
             +---- message.txt

Delete Container
       |
       V
Application deleted
message.txt deleted

With Docker Volume

Docker Host
    |
    +---- Container
    |        |
    |        +---- Application
    |        |
    |        +---- Reads/Writes data
    |                    |
    +--------------------+
    |
    +---- Docker Volume
              |
              +---- message.txt

Delete Container
       |
       V
Application deleted

Docker Volume remains
message.txt remains

Important: The container and volume have separate lifecycles.

3. Real-world example

Consider an e-commerce application.

Your application stores:

• Customer information

• Order information

• Product information

• Uploaded product images

If you store these files directly inside a container, deleting the container can result in data loss.

Instead, you can use Docker Volumes.

E-Commerce Application
        |
        V
Docker Container
        |
        +---- Application
        |
        +---- Database
                  |
                  V
             Docker Volume
                  |
                  +---- Customer Data
                  +---- Order Data
                  +---- Product Data

Even if you recreate the container, your database data remains in the volume.

4. Practical Example – Let's implement it

We will create a Docker Volume and store a message.txt file inside it.

Step 1: Create a Docker Volume

Open CMD or PowerShell:

docker volume create mydata

This creates a volume named mydata.

Step 2: Check available volumes

docker volume ls

Output:

DRIVER    VOLUME NAME
local     mydata

Step 3: Create a container and connect the volume

docker run -it --name volume-demo -v mydata:/app/data ubuntu bash

What does this command mean?

Step 4: Create a file inside the container

You are now inside the Ubuntu container.

Execute:

echo "Hello from Docker Volume!" > /app/data/message.txt

Read the file:

cat /app/data/message.txt

Output:

Hello from Docker Volume!

Step 5: Exit the container

exit

Step 6: Delete the container

Execute this from your Windows CMD:

docker rm volume-demo

We have deleted the container. But what about our file?

Step 7: Create another container using the same volume

docker run -it --name volume-demo2 -v mydata:/app/data ubuntu bash

Now execute:

cat /app/data/message.txt

Hello from Docker Volume!

Surprise! The file is still available even though we deleted the previous container.

Why? Because the file was stored in the Docker Volume, not in the container's own filesystem.

5. Where does Docker store volumes?

On Windows with Docker Desktop, Docker manages volume storage inside its Linux environment (typically its WSL2 virtual disk).

You can inspect a volume using:

docker volume inspect mydata

Docker displays information such as:

• Volume name

• Driver

• Mountpoint

• Creation date

You generally don't need to manually access this internal storage location.

6. Types of Docker Storage

Docker provides three important storage mechanisms.

docker run -v mydata:/app/data ubuntu

docker run -v "D:\MyApp:/app" ubuntu

docker run --tmpfs /app/temp ubuntu

7. Docker Volume vs Bind Mount

8. Important Docker Volume Commands

Important: Removing a volume permanently deletes its stored data. Make sure you no longer need the data before removing it.

9. Interview Questions

1. What is a Docker Volume?

2. Why do we need Docker Volumes?

3. What happens to volume data when a container is deleted?

4. What is the difference between Docker Volume and Bind Mount?

5. Where does Docker store volume data?

6. Can multiple containers share the same Docker Volume?

7. What is the difference between named volumes and anonymous volumes?

8. How do you create, inspect and delete Docker Volumes?

9. Can we use Docker Volumes with SQL Server or MySQL containers?

10. What is tmpfs mount in Docker?

10. Check your understanding