Rails 8 × Kamal 2でAWS(EC2+RDS)にデプロイする手順【2026年版】

$ rails new kamal_deploy -d postgresql

$ cd kamal_deploy

$ rails db:migrate

$ bin/dev

$ git add .
$ git commit -m "Initial commit"

root "home#index"

class HomeController < ApplicationController
  def index
  end
end

<div>
  <h1>ホーム</h1>
</div>

$ git add .
$ git commit -m "Add home"

$ touch .env

$ ssh ubuntu@パブリックIP -i ~/.ssh/<pemファイル>

$ cat ~/.ssh/id_ed25519.pub

ssh-ed25519 <your-public-key>
↑ 表示された内容をコピー

$ ssh-keygen -t ed25519 -C "your_email@example.com"

$ ssh ubuntu@パブリックIP -i ~/.ssh/<pemファイル>

$ vi ~/.ssh/authorized_keys

# 末尾に公開鍵を貼り付けて保存する

$ ssh ubuntu@パブリックIP

<% require "dotenv"; Dotenv.load(".env") %>

# Name of your application. Used to uniquely configure containers.
service: kamal_deploy

# Name of the container image.
image: <DockerHubのアカウント名>/kamal_deploy

# Deploy to these servers.
servers:
  web:
    - <EC2のパブリックIP>
  # job:
  #   hosts:
  #     - 192.168.0.1
  #   cmd: bin/jobs

# Enable SSL auto certification via Let's Encrypt and allow for multiple apps on a single web server.
# Remove this section when using multiple web servers and ensure you terminate SSL at your load balancer.
#
# Note: If using Cloudflare, set encryption mode in SSL/TLS setting to "Full" to enable CF-to-app encryption.
# proxy:
#   ssl: true
#   host: app.example.com

# Credentials for your image host.
registry:
  # Specify the registry server, if you're not using Docker Hub
  # server: registry.digitalocean.com / ghcr.io / ...
  username: <DockerHubのアカウント名>

  # Always use an access token rather than real password when possible.
  password:
    - KAMAL_REGISTRY_PASSWORD

# Inject ENV variables into containers (secrets come from .kamal/secrets).
env:
  secret:
    - RAILS_MASTER_KEY
    - DATABASE_USERNAME
    - DATABASE_PASSWORD
    - DATABASE_HOST
  clear:
    # Run the Solid Queue Supervisor inside the web server's Puma process to do jobs.
    # When you start using multiple servers, you should split out job processing to a dedicated machine.
    SOLID_QUEUE_IN_PUMA: true

    # Set number of processes dedicated to Solid Queue (default: 1)
    # JOB_CONCURRENCY: 3

    # Set number of cores available to the application on each server (default: 1).
    # WEB_CONCURRENCY: 2

    # Match this to any external database server to configure Active Record correctly
    # Use kamal_deploy-db for a db accessory server on same machine via local kamal docker network.
    # DB_HOST: 192.168.0.2

    # Log everything from Rails
    # RAILS_LOG_LEVEL: debug

# Aliases are triggered with "bin/kamal <alias>". You can overwrite arguments on invocation:
# "bin/kamal logs -r job" will tail logs from the first server in the job section.
aliases:
  console: app exec --interactive --reuse "bin/rails console"
  shell: app exec --interactive --reuse "bash"
  logs: app logs -f
  dbc: app exec --interactive --reuse "bin/rails dbconsole"


# Use a persistent storage volume for sqlite database files and local Active Storage files.
# Recommended to change this to a mounted volume path that is backed up off server.
volumes:
  - "kamal_deploy_storage:/rails/storage"


# Bridge fingerprinted assets, like JS and CSS, between versions to avoid
# hitting 404 on in-flight requests. Combines all files from new and old
# version inside the asset_path.
asset_path: /rails/public/assets

# Configure the image builder.
builder:
  arch: amd64

  # # Build image via remote server (useful for faster amd64 builds on arm64 computers)
  # remote: ssh://docker@docker-builder-server
  #
  # # Pass arguments and secrets to the Docker build process
  # args:
  #   RUBY_VERSION: 3.3.6
  # secrets:
  #   - GITHUB_TOKEN
  #   - RAILS_MASTER_KEY

# Use a different ssh user than root
ssh:
  user: ubuntu

# Use accessory services (secrets come from .kamal/secrets).
# accessories:
#   db:
#     image: mysql:8.0
#     host: 192.168.0.2
#     # Change to 3306 to expose port to the world instead of just local network.
#     port: "127.0.0.1:3306:3306"
#     env:
#       clear:
#         MYSQL_ROOT_HOST: '%'
#       secret:
#         - MYSQL_ROOT_PASSWORD
#     files:
#       - config/mysql/production.cnf:/etc/mysql/my.cnf
#       - db/production.sql:/docker-entrypoint-initdb.d/setup.sql
#     directories:
#       - data:/var/lib/mysql
#   redis:
#     image: redis:7.0
#     host: 192.168.0.2
#     port: 6379
#     directories:
#       - data:/data

KAMAL_REGISTRY_PASSWORD=<DockerHubのアクセストークン>

DATABASE_USERNAME=<RDSのマスターユーザー>
DATABASE_PASSWORD=<RDSのマスターパスワード>
DATABASE_HOST=<RDSのエンドポイント>

KAMAL_REGISTRY_PASSWORD=$KAMAL_REGISTRY_PASSWORD

# Improve security by using a password manager. Never check config/master.key into git!
RAILS_MASTER_KEY=$(cat config/master.key)

DATABASE_USERNAME=$DATABASE_USERNAME
DATABASE_PASSWORD=$DATABASE_PASSWORD
DATABASE_HOST=$DATABASE_HOST

production:
  primary: &primary_production
    <<: *default
    database: kamal_deploy_production
    username: <%= ENV["DATABASE_USERNAME"] %>
    password: <%= ENV["DATABASE_PASSWORD"] %>
    host: <%= ENV["DATABASE_HOST"] %>

$ git add .
$ git commit -m "Setup deploy"

$ bin/kamal setup

$ sudo usermod -aG docker $USER && newgrp docker

$ bin/kamal deploy

proxy:
  ssl: true
  host: app.example.com

$ bin/kamal deploy