Lesson 8 - Docker Storage

Managing data in Docker requires an understanding of the storage mechanisms Docker provides. Each mechanism has its own advantages and disadvantages, suitable for specific use cases. Below is a more detailed look at how to use and manage data in Docker through Volumes, Bind Mounts, and tmpfs Mounts.

Using Volumes in Docker

Volumes are the preferred choice for persistent data storage as they are managed by Docker and detached from the lifecycle of a container.

Creating and managing Volumes:

1. Create a new Volume:

   docker volume create my_volume
   

2. List existing Volumes:

   docker volume ls
   

3. Run a container and attach a Volume:

   docker run -v my_volume:/app/data <image_name>
   

   Here, my_volume is the name of the volume, and /app/data is the mount point inside the container.

4. Inspect details about a Volume:

   docker volume inspect my_volume
   

Using Bind Mounts

Bind Mounts allow you to mount any directory on the host machine into a container. The data is stored directly on the host’s filesystem and can be easily accessed from both the host and the container.

How to use Bind Mounts:

docker run -v /path/on/host:/path/in/container <image_name>

For example, to mount the /src directory on the host to the /app directory in the container:

docker run -v /src:/app <image_name>

Note: Bind Mounts can pose security risks if not used carefully, as they allow containers direct access to the host’s filesystem.

Using tmpfs Mounts

Tmpfs Mounts create a temporary memory partition in the host’s RAM, providing a way to store temporary data without writing to disk.

Launching a container with tmpfs Mounts:

docker run --tmpfs /path/in/container <image_name>

For example, to create a tmpfs mount at /app/cache inside the container:

docker run --tmpfs /app/cache <image_name>

Data in tmpfs mounts is deleted when the container stops or is removed, making them an ideal choice for data that requires temporary storage or high security.

Choosing the Right Storage Method

When deciding how to store data in Docker, consider the following:

• Does the data need to persist across container restarts? Use Volumes.
• Does the data need to be managed outside of Docker and easily accessible from the host? Consider using Bind Mounts.
• Is the data only temporary and not needed after the container stops? Tmpfs Mounts are a good choice.

Remember, each storage method has its own pros and cons, and the choice of the right method depends on the specific requirements of your application and your deployment environment.