Docker Volumes Explained – Differences Between Named Volumes, Anonymous Volumes and Bind Mounts Volumes

What is a Docker volume?

A Docker volume is a persistent storage mechanism that allows data to be saved and reused across the lifecycle of Docker containers. Unlike the container’s filesystem, which is ephemeral and gets deleted when the container is removed, volumes allow data to persist independently of the container itself.

Key Characteristics of Docker Volumes:

• Data Persistence: Volumes ensure that data stored in them is not deleted when a container is removed or stopped. They are ideal for databases, logs, or any other data that needs to persist.
• Decoupled from Containers: Volumes are not tied to a specific container. They can be shared between multiple containers, allowing for easy data sharing.
• Docker Managed: Docker takes care of managing volumes (e.g., their storage location and life cycle) without requiring you to handle those tasks directly. Volumes are usually stored in a specific location on the host system (/var/lib/docker/volumes/ on Linux).
• Better Performance: Compared to bind mounts (which directly mount files from the host filesystem), volumes are typically optimized for Docker and offer better performance in certain scenarios.

Use Cases for Docker Volumes:

1. Persisting Database Data: You might use a volume to store a database’s data so that it persists even if the container running the database is stopped or removed.
2. Sharing Data Between Containers: Volumes allow multiple containers to share data. For example, a web server and a backup service might share the same volume to access files.
3. Avoiding Data Loss: Since the container filesystem is ephemeral (it is deleted when the container is removed), storing important data in a volume ensures it is preserved.

Types of Docker Volumes:

1. Named Volumes: Explicitly created by the user and can be referenced by name. Docker manages their storage location.
2. Anonymous Volumes: Automatically created by Docker when a user doesn’t specify a name. They function similarly to named volumes but are harder to manage since they don’t have a name.
3. Bind Mounts: These are not managed by Docker. Instead, a directory or file from the host system is directly mounted into the container.

Example of Using a Volume in Docker:

Here’s an example of how to create a volume and use it in a container:

# Create a named volume
docker volume create my_volume_name

# Run a container and mount the volume
docker run -d --name my_container -v my_volume:/app/data nginx

In this example:

• my_volume is the Docker-managed volume.
• The volume is mounted to /app/data inside the container.
• The container is running an Nginx server (nginx image).

With this setup, any data written to /app/data inside the container will be persisted in the my_volume volume, even if the container is removed.

Let me know if you need more details or examples! In part 2 of this article we will explain the differences between named volumes, anonymous volumes and bind mounts.

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