FlashDrive automatically builds your Ruby app.
In order to do that FlashDrive uses buildpacks to detect and build automatically your app.

FlashDrive requires several files to be placed inside the root directory of your app to be able to build it :

  • Gemfile (and Gemfile.lock generated by the bundle install command)
  • Procfile

You can fork or build this repository to get started with Ruby on FlashDrive

Create your app on FlashDrive

Create a new app and link it with your repository using SSH keys.

Read this article for a detailed procedure or check this video :


A Gemfile is mandatory for your app to be able to build. Gemfile is the main configuration file of your Ruby app.

Run locally bundle install to generate the Gemfile.lock and make sure it’s available on your repository before building your app.

Specifying the Ruby version

FlashDrive lets you build with different Ruby implementations. You can configure your app to select a specific runtime.

If your Gemfile does not contain a ruby entry, you will get MRI 2.6.6

The builder automatically uses the last available version if a ruby version is not specified. There is no lock-in to a specific version like with several other cloud providers.

We highly recommend specify a Ruby version in your Gemfile and not relying on the default Ruby version.

Supported runtimes

FlashDrive supports the following versions of Ruby and the associated Rubygems :


  • 2.6.8, Rubygems:
  • 2.7.4, Rubygems: 3.1.6
  • 3.0.2, Rubygems: 3.2.22


  •, Ruby Versions: [2.3.3]
  •, Ruby Versions: [2.5.8]

You can use the ruby keyword in your app’s Gemfile to specify a specific version of Ruby :

source ""
ruby "2.5.1"

For specifying non-MRI Ruby engines, you’ll need to use the :engine and :engine_version options. You can specify JRuby by using the following line:

ruby "2.2.2", :engine => "jruby", :engine_version => ""


The Procfile informs the engine of the type of app you are running (web or worker) and prepares the infrastructure accordingly. Make sure to use the same server type as during the app creation (web or worker) or you will need to manually alter the networks settings of the app.

The Procfile basically contains the type of app and the initial script to run when the app starts :

web: bundle exec ruby server.rb

Declare app dependencies

FlashDrive uses the Gemfile to build dependencies and it must contain all the dependencies your app needs to run.

A gemfile.lock file must also be committed to your repository, check the section “prepare your app”.

For instance in our example the Gemfile looks like that :

# frozen_string_literal: true

source ""

git_source(:github) {|repo_name| "{repo_name}" }

# gem "rails"

gem "puma", "~> 4.3"

gem "sinatra", "~> 2.0"

gem "cowsay", "~> 0.3.0"

Default Behavior

By default, your Ruby app is routed to the 8080 port of the container. If you need to change the instance port of your app you can do it from the app settings page by changing the network setting and the environment variable.

Note: you can set up any container port but FlashDrive will only route 80/443 traffic to your app. FlashDrive’s are not reachable from the outside of FlashDrive on any other port.

Support for Rack and additional buildpack support

The support for rack-based servers is not supported by default inside the Ruby buildpack. Adding a file will automatically add the buildpack and support for Rack-based servers to start the application.

The additional Ruby buildpack can also be activated without a file from the add-on library.

Create persistent storage

One of the major improvements of FlashDrive in comparison to other app hosting solutions is the ability to create Virtual Disks available for any copy of your app inside the same stack.

Virtual disks allow you to store data safely and securely, without the need to use an additional S3 bucket, and every app size gets free disk space depending on its size (see our pricing for more information).

In addition to that, Virtual disks are backup every day with 10 days history and ransomware protection at no additional cost.

Read this article for more informations about virtual disks and how to add one to your app.

Add a domain name

Please check this article for a detailed method on how to use your domain name with FlashDrive apps.

Define environment variables

Note: Environment variables set in your app settings are injected during the build process. If the build of your app needs to use an env variable make sure to set it before requesting the build.

FlashDrive lets you externalize the configuration of your app : the FlashDrive cluster will automatically injects the data when the app start or restart.

Environment variables can include any external data your app needs to run like external resources, databases addresses, encryption keys, etc…

To add an environment variable, access your app settings and click “Add ENV Variable” :

Enter the key (like DATABASE_USER) and the value and click “Add”. FlashDrive will automatically add your environment variable and restart your app after a one-minute delay (to let you add more env variables if necessary without restarting the app each time a new variable is added).

Provision a database

FlashDrive Marketplace includes all popular datastore engines including Mysql, Postgres, MongoDB, and Redis.
To add a database to your app, click on Marketplace and select the database you want to run, then create the new app database inside the same stack as your Ruby app.

Once the app is running, visit the database app’s settings and retrieve the “internal name” :

Use this internal name as you would use a server address, for instance for MySQL this name replaces the usual “localhost”. Some scripts require you to add the database port at the end of the server address. FlashDrive uses a common port for each database software, for MySQL it will be 3306 and you can write it like that inside your scripts: internal-name:3306
Postgres usually uses credentials sent inside the login URL, like that : postgres://<user>:<password>@<internalname>:5432/<database>

The login and password information is available inside the Environment Variables of the database app.

Reach your app from another app

Inside your app stack, you can reach any other FlashDrive app member of this stack on any port. FlashDrive automatically routes the traffic internally and opens the appropriate port. By opposition, your app is only reachable on ports 80/443 from outside of FlashDrive.

To reach your app internally, retrieve the internal name from your app settings page :

This name can be used to reach your app from another app inside the same stack. Use it in any form that works with your script :


Note: https:// is not available, all the traffic inside apps is already encrypted by the cluster.


FlashDrive uses at rest encryption for the app virtual disks, build images, and encrypted transport from inside the cluster. To make sure the traffic is encrypted between your app and the browser of your users you can set up SSL certificates for any domain name connected to the app (including the FlashDrive’s default domain name).

Scale your App

From your app settings you can scale your app vertically and horizontally: by upgrading the app size (refer to our pricing for app sizes details) or by adding more nodes.

Additional nodes will run another copy of your app inside another FlashDrive server located inside the same cluster (same geographical location). Traffic is automatically sent to the least occupied node by FlashDrive’s load balancer.

Note: Apps that use Virtual Disks will share the same file structure and read/write on the same disk. It’s fine in most cases for intensive read activity but can create bottlenecks and corrupted data if several nodes of the same app write on the same file at the same time. If your apps use intensive reads on virtual disks consider upgrading the app size instead of adding more nodes.

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