What are Docker Volumes?

By default, data inside a Docker container is lost when the container stops or is deleted. Docker Volumes solve this problem by providing a way to persist data outside the container lifecycle.

Volumes are managed by Docker and stored on the host filesystem.

Types of Docker Storage

Volume Commands

Example 1: Create and Use a Volume

# Create a named volume
docker volume create my-data

# Run a container with the volume mounted
docker run -d --name my-container -v my-data:/app/data ubuntu

Any data written to /app/data inside the container will be saved in the my-data volume.

Example 2: Bind Mount (Map Host Folder)

# Map current host folder to container /var/www/html
docker run -d --name my-nginx -p 8080:80 -v $(pwd)/html:/usr/share/nginx/html nginx

Changes to files in your local html folder are immediately reflected inside the container.

Example 3: MySQL with Persistent Volume

docker run -d --name mysql-db -e MYSQL_ROOT_PASSWORD=secret -e MYSQL_DATABASE=mydb -v mysql-data:/var/lib/mysql mysql:8.0

MySQL data is now persisted in the mysql-data volume even if the container is deleted.

Example 4: Inspect a Volume

docker volume inspect mysql-data

Output:

[
    {
        "Name": "mysql-data",
        "Driver": "local",
        "Mountpoint": "/var/lib/docker/volumes/mysql-data/_data"
    }
]

Volume vs Bind Mount

Summary

• Docker volumes persist data beyond the container lifecycle.
• Use named volumes for production data (MySQL, uploads, etc.).
• Use bind mounts during development for live code reloading.
• Clean up unused volumes with docker volume prune.