Creating a custom image only requires a Dockerfile with a FROM directive, but since this only renames the image, how do we actually change it? When building a custom image, we often need to add files. Whether they are config files, scripts, compressed archives, or even application binaries, Docker makes it easy to add a file to an image with just one directive.

In this tutorial, we'll:

• Describe how to position files relative to your Dockerfile
• Use the COPY directive to add local files
• Download remote files using the ADD directive

The COPY and ADD directives make it easy to add configuration files or download archives to a container image. While we could install applications into a container using only those directives, it would be difficult and complex. Making matters worse, Docker provides no INSTALL directive. Instead, Docker provides a more general mechanism.

In this tutorial, we'll:

• Introduce the RUN directive and how to run commands during a docker build
• Use package managers to install applications
• Describe best practices for installing software in images

Installation is only one part of setting up a custom Docker image. With few exceptions, we'll want to configure the application to better suit our use case. Docker does not provide a standardized way for applications to be configured. Instead, we rely on the same techniques as we would when configuring the application on a bare-metal server.

In this tutorial, we'll:

• Extract default configuration files from a Docker image
• Give strategies for adding configuration files to the image
• Outline the complexities of using configuration commands in a Dockerfile

The goal of Docker containers is to let you select pieces of technical infrastructure as if you were pulling items off of a shelf. Toward that end, each container image can be configured with a default application to invoke when started with a docker run or as part of a container set with docker-compose up.

In this tutorial, we'll:

• Describe the difference between the build-time and runtime environment of a container
• Use the CMD directive to specify a default command to execute
• Introduce the ENTRYPOINT directive and set a default shell in which to run your CMD

The ENTRYPOINT directive allows us to specify a default shell to use in our custom image, but it can do more than that. Often, we will want to dynamically configure a container on startup by passing it environment variables or using Docker Secrets. By replacing the ENTRYPOINT with a custom script, we can perform this dynamic configuration prior to executing the default application.

In this tutorial, we'll:

• Introduce custom entrypoint scripts
• Describe several strategies for performing dynamic configuration in a container

Often you'll find an image on Docker Hub that almost fits your requirements. For Drupal developers, often the off-the-shelf containers for PHP just aren't enough. Drupal often requires additional PHP extensions such as mbstring or gd. We may also want to use a slightly different configuration, or bake-in a utility like Drush or Drupal Console. Fortunately, Docker makes modifying existing containers easy in a Dockerfile.

In this tutorial, we'll:

• List the reasons why you might modify an existing image
• Describe the general process by which an existing image is modified

When writing containers for a local development environment, security is often a lesser concern. This is fine as long as we never intend to put the containers we create in a production environment.

When we do want to make production-ready containers, however, our priorities change. While Docker tries to be secure by default, it can't protect us from badly configured or vulnerable applications. For that, we need to design our images to be more secure.

In this tutorial, we'll:

• Outline the best practices for writing secure container images
• Introduce the USER directive
• Set file ownership using COPY and ADD
• Use the RUN directive to set file permissions

Getting Drupal to run in Docker requires a lot of moving parts. After installing Docker and Docker Compose, we need to select a collection of containers from Docker Hub and create a new docker-compose.yml file. Once we have environment variables and volumes configured, this only gives us the capability of running a Drupal site in Docker.

What if we already have a Drupal site we want to develop using Docker? In this tutorial, we'll show how to modify an existing project to minimize the setup time necessary for switching to a Docker-based environment.

In this tutorial, we'll:

• Describe the best practices for project organization.
• Use an environment file to configure containers.
• Add a Docker-specific settings.php file.

Dockerizing a project helps to simplify setting up new developer workstations, and on-boarding new team members. All the pieces of infrastructure necessary to get started are all in the Compose file. Yet, it's not as easy as it could be.

We still need to create a settings.local.php file with all the necessary database connection information and any setting overrides. In this tutorial, we'll move those out of the local settings file and into a Docker specific settings file that ships with all that information pre-configured out of the box.

In this tutorial, we'll:

• Explain the motivation behind having a Docker-specific settings file.
• Describe how to modify settings.php to detect when it's in a Docker environment.
• Create a Docker-specific settings file with everything preconfigured.

One of the problems with Dockerizing an existing project is that configuration information tends to proliferate everywhere. Not only do we have settings in docker-compose.yml, but also in our Docker-specific settings file settings.docker.php. If we change a setting in one place we need to copy and paste it everywhere else. This can make things difficult if we suddenly have the need to change a setting.

Fortunately, there's a way to centralize Docker configuration for our project by using an environment file.

In this tutorial, we'll:

• Review what an environment file is and its format.
• List the advantages of moving Docker configuration to an environment file.
• Describe the .env file, and how it provides us further advantages.

Throughout this series we've been focused on working with a single set of containers and a single site. For most Drupal developers, however, we're expected to work with multiple client sites, sometimes several different ones in the same day.

When we add Docker into the mix, it can seem overwhelmingly complicated when you're used to working with other tools. Fortunately, there are several simple practices that not only work well with Docker, but also support your workflow.

In this tutorial, we'll:

• Outline the best practices when building a local development environment in Docker.
• Compare the differences in workflow when using Docker compared to other local development environments.
• Discuss various strategies to reduce resource use on team workstations.

Today's Drupal sites often rely upon external services in order to serve their visitors. When hosting such a site in Docker, we need to take special consideration in order to allow the site to access these essential components.

In this tutorial, we'll:

• Outline the steps necessary for troubleshooting connectivity issues
• Discuss steps to protect API keys and other sensitive pieces of information
• Touch upon your options if you require external libraries or utilities

One of the key advantages of Docker is that it makes it much easier to share your containers with your team members. For most of this series, we've been relying on containers hosted on Docker Hub. When we need to create a custom container for our team, we want to leverage that same sharing infrastructure.

In this tutorial, we'll:

• Describe the various methods of sharing containers.
• Outline the advantages of using Docker Hub.
• Briefly describe why and when you should use a private container image registry.

For many container images on Docker Hub, the preferred approach is to create an automatic build. An automatic build integrates Hub with a public Git repository, providing you an effective, open, and best-practice approach to sharing your containers with your team, and with the world.

In this tutorial, we'll:

• List the advantages of creating an automatic build compared to other approaches on Docker Hub.
• Describe the process of creating an automatic build.
• Outline how to organize your git repository for your images.
• Learn how to configure and trigger the build on Hub.

Often it's useful for a container image to provide several variants of itself under the same name on Docker Hub. Docker uses tags to identify these variants. You can configure your own tags as part of your automatic build on Docker Hub.

In this tutorial, we'll:

• Outline the uses for tags
• Discuss the best practices for tag names
• Learn how to add tags to your automatic build on Docker Hub

Docker Hub provides a free, easy to use way of distributing your container images. However, there are situations where sharing your container images is either not ideal, bad practice, or against legal requirements. In those cases, you will want to use a private registry instead.

In this tutorial, we'll:

• Describe what a private registry is.
• Learn how to run Docker's own registry image.
• Learn how to push and pull images from the self-hosted registry.
• Outline the production concerns for the registry image.
• List other options for self-hosting your own images.

Docker provides numerous advantages for us as Drupal developers. It simplifies the management of infrastructure for our projects while allowing customization to suit each project's needs. Running Docker in production also brings a number of advantages, but it also creates new concerns.

In this tutorial, we'll:

• Outline the advantages Docker brings to the production environment.
• Highlight the concerns when planning a production deployment of Docker.
• Describe container orchestration and list several container orchestration platforms to choose from.

Often, there's an existing Drush command that does most of what you want, but needs just a few tweaks or enhancements to make it meet your project requirements. Maybe the existing core Drush command has the functionality but lacks some additional validation. Or maybe you need to add an option to perform some application-specific debugging logic for all commands in a group.

Drush hooks can be used to alter, extend, and enhance existing Drush commands.

In this tutorial we'll:

• Learn how to alter a Drush command with code in a custom module
• Declare a validation hook that alters the user:password command with additional password validation logic

By the end of this tutorial you should be able to alter a Drush command provided by Drush core or a contributed module with your own custom code.

Back-end developers, and Drupal site builders, often find themselves having to perform the same UI steps over and over again, like exporting configuration, importing configuration changes, running cron, processing a large queue of jobs, indexing items for Search API, and more. Performing these tasks with Drush saves time and reduces the number of clicks required.

Drush core contains commands to execute all the most common tasks. Many contributed modules provide their own Drush commands to make interaction with the module's features, easier, faster, and scriptable.

In this tutorial we'll:

• Learn about the Drush core commands for common tasks like interacting with queues, performing database backups, and importing/exporting configuration
• Demonstrate how to find the Drush commands provided by contributed modules in your project

By the end of this tutorial you'll learn some popular commands for common tasks that'll speed up your daily work.

Every Drupal site consists of many Drupal projects like modules and themes. Drush comes with a group of commands that aid in managing projects from the command line. These commands can check which modules are present in a site's codebase, report their security status, enable modules, and display metadata for modules and themes. All of these commands start with the pm prefix, and are part of the project manager group.

Common use cases for the project manager commands include: quickly enabling/disabling modules via the CLI rather than performing numerous clicks in the UI, and as part of CI/CD process that lists (or maybe even automates) security updates.

In this tutorial we'll:

• List the available pm commands
• Enable a module with Drush
• Uninstall a module with Drush
• Use Drush to check for security updates for modules, themes and PHP packages

By the end of this tutorial you'll have an understanding of the project manager commands that come with Drush, how to use them, and how to speed up common workflows and maintenance tasks.