Category: docker

Docker containers are easiest to use with stateless applications because their filesystems are ephemeral in nature. Changes made to a container’s environment are lost when the container stops, crashes, or gets replaced.

You can Dockerize stateful applications such as databases and file servers by attaching volumes to your containers. Volumes provide persistent storage that’s independent of individual containers. You can reattach volumes to a different container after a failure or use them to share data between several containers simultaneously.

In this article, you’ll learn what volumes are and the use cases they enable. We’ll also cover some practical examples of using volumes with Docker and Docker Compose.

What Are Docker Volumes?

Volumes are a mechanism for storing data outside containers. All volumes are managed by Docker and stored in a dedicated directory on your host, usually /var/lib/docker/volumes for Linux systems.

Volumes are mounted to filesystem paths in your containers. When containers write to a path beneath a volume mount point, the changes will be applied to the volume instead of the container’s writable image layer. The written data will still be available if the container stops – as the volume’s stored separately on your host, it can be remounted to another container or accessed directly using manual tools.

Volumes work with both Linux and Windows containers. Several different drivers are available to store volume data in different services. Local storage on your Docker host is the default, but NFS volumes, CIFS/Samba shares, and device-level block storage adapters are available as alternatives. Third-party plugins can add extra storage options too.

Introduction

Docker is an application that simplifies the process of managing application processes in containers. Containers let you run your applications in resource-isolated processes. They’re similar to virtual machines, but containers are more portable, more resource-friendly, and more dependent on the host operating system.

For a detailed introduction to the different components of a Docker container, check out The Docker Ecosystem: An Introduction to Common Components.

In this tutorial, you’ll install and use Docker Community Edition (CE) on Ubuntu 20.04. You’ll install Docker itself, work with containers and images, and push an image to a Docker Repository.

In this article, we’ll share the basics of what Compose is and how to use it. We’ll also provide some examples of using Compose to deploy popular applications. Let’s get started!

We will cover:

1. What is Docker Compose
2. Docker Compose benefits
3. Using Docker Compose
4. Docker Compose usage examples

What is Docker Compose?

Docker Compose is a tool that makes it easier to create and run multi-container applications. It automates the process of managing several Docker containers simultaneously, such as a website frontend, API, and database service.

Docker Compose allows you to define your application’s containers as code inside a YAML file you can commit to your source repository. Once you’ve created your file (normally named docker-compose.yml), you can start all your containers (called “services”) with a single Compose command.

Compared with manually starting and linking containers, Compose is quicker, easier, and more repeatable. Your containers will run with the same configuration every time—there’s no risk of forgetting to include an important docker run flag.

Compose automatically creates a Docker network for your project, ensuring your containers can communicate with each other. It also manages your Docker storage volumes, automatically reattaching them after a service is restarted or replaced.