Development container is a full-featured coding environment. Rails 7.2 introduces configurations for these containers in your application, including a .devcontainer folder with Dockerfile, docker-compose.yml, and devcontainer.json.

The default dev container includes:

• A database (SQLite, Postgres, MySQL, or MariaDB)
• Active Storage with local disk usage and preview features
• A Redis container
• A Headless Chrome container for system tests

Generate a new application with a development container using:

rails new myapp --devcontainer

After this, you will see the result of the generator:

      ...
      create  storage/.keep
      create  tmp/storage
      create  tmp/storage/.keep
      create  .devcontainer
      create  .devcontainer/devcontainer.json
      create  .devcontainer/Dockerfile
      create  .devcontainer/compose.yaml
      ...

As you can see, the generator created files that correspond to the container configuration.

For existing applications, use:

rails devcontainer

Result:

╰─ $ rails devcontainer
Generating Dev Container with the following options:
app_name: rails_blog
database: sqlite3
active_storage: true
redis: true
system_test: true
node: false
      create  .devcontainer
      create  .devcontainer/devcontainer.json
      create  .devcontainer/Dockerfile
      create  .devcontainer/compose.yaml
        gsub  test/application_system_test_case.rb

More details in the Getting Started with Dev Containers guide.

We have previously written about how to set up Docker for Ruby on Rails 7. In this article you can find more detailed information on how to configure docker:
Setting Up Docker for Ruby on Rails 7