Miget Buildpacks automatically detect and build your Ruby applications when you select Auto detection (Miget Buildpacks) as the build method. Rails applications are fully supported with asset precompilation and native gem handling. For the full reference, visit the migetpacks Ruby documentation.

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Detection

Your application is detected as Ruby when one of these files is present in the root directory:
  • Gemfile
  • Rakefile
  • config.ru

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Version Detection

The Ruby version is determined from the following sources, in order of priority:
  1. .ruby-version
  2. ruby directive in Gemfile
If no version is specified, a recent stable Ruby version is used.

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Build Process

During the build, the following steps are performed:
  1. Bundler version detection - The Bundler version is auto-detected from the BUNDLED WITH section in Gemfile.lock.
  2. Dependency installation - Gems are installed via Bundler.
  3. Native gem support - Native gems such as pg, mysql2, sqlite3, and nokogiri are auto-detected, and the required system libraries are installed automatically.
  4. Rails support - If Rails is detected:
    • Asset precompilation runs automatically.
    • Runtime cleanup removes unnecessary build artifacts.

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Run Command

The run command is resolved in the following order:
  1. web process in a Procfile
  2. Rails server (if Rails is detected)
  3. rackup (if config.ru is present)
You can also override the run command directly in the Miget dashboard when creating your app or changing the deployment source.
Builder settings showing Run Command override

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Configuration

You can customize the build and runtime behavior through the Miget dashboard and repository configuration files:
  • Environment variables - Set under Settings -> Variables in the Miget dashboard
  • Procfile - Define the start command at the root of your repository
  • app.json - Application manifest for additional configuration
  • Project Path - For monorepo setups, specify the subdirectory containing your application code in the Advanced tab
  • Pre-Deploy Command - Run a command before deployment (e.g., database migrations) in the Advanced tab
  • Post-Deploy Command - Run a command after successful deployment (e.g., seeding data, cache warming) in the Advanced tab

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Docker Hardened Images

You can enable Docker Hardened Images (DHI) in the Advanced tab when creating your app or changing the deployment source. When enabled, your application is built using distroless runtime images with a minimal attack surface, no shell, and no package manager.
Advanced builder settings with Docker Hardened Images toggle
Native gem libraries are automatically copied into the hardened image.
For the complete reference, see the migetpacks Ruby documentation.