---
title: Containerize a Ruby on Rails application
linkTitle: Containerize your app
weight: 10
keywords: ruby, flask, containerize, initialize
description: Learn how to containerize a Ruby on Rails application.
aliases:
  - /language/ruby/build-images/
  - /language/ruby/run-containers/
  - /language/ruby/containerize/
  - /guides/language/ruby/containerize/
---

## Prerequisites

- You have installed the latest version of [Docker Desktop](/get-started/get-docker.md).
- You have a [Git client](https://git-scm.com/downloads). The examples in this section show the Git CLI, but you can use any client.

## Overview

This section walks you through containerizing and running a [Ruby on Rails](https://rubyonrails.org/) application.

Starting from Rails 7.1 [Docker is supported out of the box](https://guides.rubyonrails.org/7_1_release_notes.html#generate-dockerfiles-for-new-rails-applications). This means that you will get a `Dockerfile`, `.dockerignore` and `bin/docker-entrypoint` files generated for you when you create a new Rails application.

If you have an existing Rails application, you will need to create the Docker assets manually. Unfortunately `docker init` command does not yet support Rails. This means that if you are working with Rails, you'll need to copy Dockerfile and other related configurations manually from the examples below.

## 1. Initialize Docker assets

Rails 7.1 generates multistage Dockerfile out of the box, below is an example of such file generated from a Rails template.

> Multistage Dockerfiles help create smaller, more efficient images by separating build and runtime dependencies, ensuring only necessary components are included in the final image. Read more in the [Multi-stage builds guide](/get-started/docker-concepts/building-images/multi-stage-builds/).

Although the Dockerfile is generated automatically, understanding its purpose and functionality is important. Reviewing the following example is highly recommended.


```dockerfile {title=Dockerfile}
# syntax=docker/dockerfile:1
# check=error=true

# This Dockerfile is designed for production, not development.
# docker build -t app .
# docker run -d -p 80:80 -e RAILS_MASTER_KEY=<value from config/master.key> --name app app

# For a containerized dev environment, see Dev Containers: https://guides.rubyonrails.org/getting_started_with_devcontainer.html

# Make sure RUBY_VERSION matches the Ruby version in .ruby-version
ARG RUBY_VERSION=3.3.6
FROM docker.io/library/ruby:$RUBY_VERSION-slim AS base

# Rails app lives here
WORKDIR /rails

# Install base packages
# Replace libpq-dev with sqlite3 if using SQLite, or libmysqlclient-dev if using MySQL
RUN apt-get update -qq && \
    apt-get install --no-install-recommends -y curl libjemalloc2 libvips libpq-dev && \
    rm -rf /var/lib/apt/lists /var/cache/apt/archives

# Set production environment
ENV RAILS_ENV="production" \
    BUNDLE_DEPLOYMENT="1" \
    BUNDLE_PATH="/usr/local/bundle" \
    BUNDLE_WITHOUT="development"

# Throw-away build stage to reduce size of final image
FROM base AS build

# Install packages needed to build gems
RUN apt-get update -qq && \
    apt-get install --no-install-recommends -y build-essential curl git pkg-config libyaml-dev && \
    rm -rf /var/lib/apt/lists /var/cache/apt/archives

# Install JavaScript dependencies and Node.js for asset compilation
#
# Uncomment the following lines if you are using NodeJS need to compile assets
#
# ARG NODE_VERSION=18.12.0
# ARG YARN_VERSION=1.22.19
# ENV PATH=/usr/local/node/bin:$PATH
# RUN curl -sL https://github.com/nodenv/node-build/archive/master.tar.gz | tar xz -C /tmp/ && \
#     /tmp/node-build-master/bin/node-build "${NODE_VERSION}" /usr/local/node && \
#     npm install -g yarn@$YARN_VERSION && \
#     npm install -g mjml && \
#     rm -rf /tmp/node-build-master

# Install application gems
COPY Gemfile Gemfile.lock ./
RUN bundle install && \
    rm -rf ~/.bundle/ "${BUNDLE_PATH}"/ruby/*/cache "${BUNDLE_PATH}"/ruby/*/bundler/gems/*/.git && \