Caput

Caput is a Ruby gem that helps you prepare a vanilla Ubuntu server to host one or more Rails applications. It automates the steps required to make an application ready for deployment with standard Capistrano commands.

Note: Caput does not deploy the application itself. Instead, it ensures that the server and the local repository are properly configured so that deployments can be done reliably with minimal manual steps.

Deploying Rails applications to a server can be surprisingly complex. While tools like Kamal provide a modern “official” deployment approach, they often require a public container registry and additional infrastructure that many teams do not want or need. On the other hand, Capistrano has been the tried-and-true method for decades, but its setup can be tedious, especially on a fresh Ubuntu server. This gem bridges the gap: it gives you a simple Capistrano-style workflow while preparing the server and the app environment, without requiring Passenger or complex container setups. Essentially, it automates the repetitive steps needed to make a Rails app server-ready, letting you focus on your app instead of manual server configuration.

Add the gem to your Rails application's Gemfile in the development group:

group :development do
  gem 'caput', '~> 0.1.0'
end

Or install it directly:

gem install caput

Run the following in the root folder of your Rails application:

caput init

This creates a caput.conf file containing configuration for your server and deployment settings.

Edit caput.conf with the correct values for your setup:

• setup_user — user on the server with sudo access
• deploy_user — user that will own the app directories
• server — hostname or IP of the server
• app_name — short name for the Rails application
• hostname — the hostname that will be used to access the app (DNS must resolve)

Make sure MySQL and Nginx are installed on the server. Caput will notify you if these dependencies are missing.

If not already the case, update the config/database.yml file to use MySQL for storage instead of the default Sqlite3. The below section can be used as a template.

  primary: &production_primary
    adapter: mysql2
    encoding: utf8mb4
    database: <%= Rails.application.credentials.dig(:mysql, :database) %>
    username: <%= Rails.application.credentials.dig(:mysql, :username) %>
    password: <%= Rails.application.credentials.dig(:mysql, :password) %>
    host: localhost
    port: 3306
  cache:
    <<: *production_primary
  queue:
    <<: *production_primary
  cable:
    <<: *production_primary

The above also requires the database information is added to the Rails credentials file by running rails credentials:edit and adding a MySQL section.

  database: <DATABASE NAME>
  username: <DATABASE USERNAME>
  password: <DATABASE PASSWORD>

The database name is typically the application name suffixed with '_production'.

Run:

caput server

Caput will:

• Validate prerequisites (MySQL client/server, Nginx, setup user, DNS)
• Create the Capistrano-compatible folder structure
• Set up a systemd service for Puma to serve requests in the background
• Configure permissions for the deploy user

Caput does not deploy the Rails app. After this, you can deploy using standard Capistrano commands.

Run:

caput local

This will:

• Add Capistrano configuration and necessary files to your local Rails repository
• Make the repository ready for deployments

Once the above has been performed, the application can be deployed using standard Capistrano commands.

• Only a few prerequisites must be handled manually: MySQL, Nginx, setup user with sudo access, and DNS for the application hostname.
• Caput is designed to allow hosting multiple Rails applications on the same server. Each application gets its own folder structure, systemd service, and Nginx configuration.