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.

As new major versions of Drupal are released, contributed modules need to be updated for compatibility. As of right now (October 2021) there are a lot of contributed modules with a Drupal 8 release and a patch in the queue to make them work with Drupal 9. However, there's no official Drupal 9 compatible release for the module, so the module can't be installed with Composer. This creates a circular problem where you can't composer require the module if you don't patch it, but you can't patch it until after it's been downloaded by Composer.

To help solve this common issue, Drupal.org provides a lenient Composer endpoint that publishes all modules as compatible with Drupal 9 regardless of whether that's true or not. By using it, you can composer require the module and then use cweagans/composer-patches to apply any necessary patches.

In this tutorial we'll:

• Add the lenient Composer endpoint to our project's composer.json file
• composer require a non-Drupal 9 compatible module
• Use Composer to download and apply a patch that makes the module Drupal 9 compatible

By the end of this tutorial you should be able to use contributed modules that require a patch to be compatible with Drupal 9.

There’s no one-size-fits-all path to upgrade from Drupal 9 to Drupal 10, but there is a set of common tasks that everyone will need to complete.

In this tutorial we’ll:

• Explain the differences between Drupal 9 and Drupal 10 that affect the upgrade path.
• Walk through the high-level steps required to upgrade from Drupal 9 to Drupal 10.
• Provide resources to help you create an upgrade checklist and start checking items off the list.

By the end of this tutorial you should be able to explain the major differences between Drupal 9 and 10, audit your existing Drupal 9 projects for Drupal 10 readiness, estimate the level of effort involved, and start the process of upgrading.

There’s no one-size-fits-all path to upgrade from Drupal 8 to Drupal 9, but there is a set of common tasks that everyone will need to complete.

In this tutorial we’ll:

• Explain the differences between Drupal 8 and Drupal 9 that affect the upgrade path.
• Walk through the high-level steps required to upgrade from Drupal 8 to Drupal 9.
• Provide resources to help you create an upgrade checklist and start checking items off the list.

By the end of this tutorial you should be able to explain the major differences between Drupal 8 and 9, audit your existing Drupal 8 projects for Drupal 9 readiness, estimate the level of effort involved, and start the process of upgrading.

Local task links are the tabs you see when logged in as an administrator viewing a node on a Drupal site. In this tutorial we'll take a look at how local tasks are added within a custom module. We'll also see how to alter local tasks provided by other modules via hook_menu_local_tasks_alter().

Drupal has long provided a built-in search mechanism, so why do we need anything more? In this tutorial, we introduce Apache Solr, a free and open source search service that has several advantages and features beyond Drupal’s built-in search.

In this tutorial, we'll:

• Define Apache Solr
• Identify Apache Lucene, the legacy name for Solr
• List key features of Solr
• Identify the advantages of Solr compared to Drupal search

Apache Solr is not a Drupal module, but a server application like Varnish or MySQL. Before we can use Solr with Drupal, we must plan how we will deploy Solr to our production site.

In this tutorial, we'll:

• List the requirements for Solr installation
• Identify when to install Solr on new hardware
• Describe various installation methods

By the end of this tutorial you should be able to describe a typical Solr install, and begin to list out the various things you'll need to do to install Solr for your environments.

Just as you would for Drupal, you should always test your search configuration prior to deploying it to production. In this tutorial, we examine the various ways to set up Apache Solr locally on your system. Then we'll walk through setting up DDEV with Solr for local development.

In this tutorial, we'll:

• Describe options for running Solr locally
• List which popular local development environments provide Solr
• Show how to set up a local, DDEV-based local dev environment with Solr

By the end of this tutorial you should be able to list the different ways that Solr can be installed locally, choose an option that works for you, and see how to get started quickly with DDEV.

Solr compartmentalizes itself into cores (or collections if you're using SolrCloud). Each Solr core has its own directory, configuration, and set of search data. While a core can be thought of as an “index”, it is much more.

In this tutorial, we'll:

• Identify the difference between a Solr core and an index.
• List the various ways a core can be created.
• Explain why Search API needs a custom core configuration.

By the end of this tutorial you should be able to explain what Solr cores are, and how to create a Solr core (or collection) that is compatible with Drupal's Search API module.