As we learned in Configuration Data Types, simple configuration is suitable for storing module settings as boolean values, integers, or text strings in one or more key/value pairs. In this tutorial, we'll walk through creating a schema and providing default configuration to store initial settings that a module needs to function.

Not every environment or copy of a site you may be working on will be created equally. You may want to enable logging on a development site or need to use different API keys depending on the environment. But you also need to make sure that your instance-specific configuration overrides don't make it into the database, mistakenly get exported, or compromise security.

In this tutorial, you will learn how to:

• Override the global $config array in settings.php (or settings.local.php)
• Retrieve overridden (immutable) configuration (read-only mode)
• Retrieve original (mutable) configuration for updating (read/write mode)
• Set dynamic values for configuration instead of overriding values

When you create a module for Drupal, it can be useful to provide default configuration. This can be settings for a form, the placement of a block, or something more complex like the default image styles provided by the Image module in core. A module can provide default configuration for simple configuration or configuration entities.

In this tutorial, we will cover:

• Possible locations for default configuration
• What happens with configuration when a module is installed or uninstalled
• Managing dependencies in configuration
• Where to find examples of default configuration

Configuration entities are suitable for creating user-defined configuration, such as image styles, views, content types, etc. A configuration entity type is defined by a module, default configuration is provided by that module as well as any other module, and then users can create zero or more configuration entities through Drupal's administrative UI.

In this tutorial, you will learn about:

• What configuration entities are
• Configuration entity types versus configuration entities
• An example in core: image style
• Overview of the process of creating your own configuration entity types in a module

When working on configuration in a module, whether as part of a migration that uses Migrate Plus configuration entities, or while developing custom configuration entities, you'll often need to re-import the configuration stored in the .yml files of the modules config/install/ or config/optional/ directories. This is tricky though, because Drupal only reads in those default configuration settings when the module is first enabled. So any changes you make to those files after the module has been installed will not be reflected without these workarounds.

Knowing how to do this can improve the developer experience of adding (or debugging) the default configuration that's provided with a module. Or for anyone using Migrate Plus configuration entities as part of a migration.

In this tutorial we'll:

• Learn about the Configuration Development module
• Look at how you can use Drush to perform a partial configuration import
• Write an implementation of hook_uninstall() to remove a module's configuration when it's uninstalled

By the end of this tutorial you should be able to re-import the configuration provided by a module without having to uninstall and then reinstall the module.

Now that we have some default simple configuration stored in a settings YAML file, let's utilize it in a form that our site administrators can use to update those values. We'll make use of some services and methods in Drupal's Configuration API in order to retrieve, update, and save simple configuration values with a form.

In this tutorial, we'll cover how to load configuration entity data in a module. We'll change the AdminSettingsForm.php we created and replace the simple textfield we were using with a dropdown select list. Then we'll use data from our Transcode Profile module's configuration entity, loaded by the EntityTypeManager via the services container, to choose our preferred Transcode Profile.

By the end of this tutorial, you should be able to:

• Know how to load configuration entities using EntityTypeManager via the services container
• Update the AdminSettingsForm.php to use a dropdown select list
• Save your preferred transcode profile from a list of transcode profile entities
• Update the default configuration provided with the demo module to include transcode profiles