Merge pull request #1614 from basecamp/dependabot/bundler/bundler-f02c9c4a61

Bump the bundler group across 1 directory with 2 updates

.github/workflows/ci.yml

@@ -0,0 +1,54 @@
+name: CI
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
+jobs:
+  rubocop:
+    name: RuboCop
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_ONLY: rubocop
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      - name: Setup Ruby and install gems
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 3.3.0
+          bundler-cache: true
+      - name: Run Rubocop
+        run: bundle exec rubocop --parallel
+  tests:
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby-version:
+          - "3.2"
+          - "3.3"
+          - "3.4"
+        gemfile:
+          - Gemfile
+          - gemfiles/rails_edge.gemfile
+    name: ${{ format('Tests (Ruby {0})', matrix.ruby-version) }}
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_GEMFILE: ${{ github.workspace }}/${{ matrix.gemfile }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Remove gemfile.lock
+        run: rm Gemfile.lock
+
+      - name: Install Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+          bundler-cache: true
+
+      - name: Run tests
+        run: bin/test
+        env:
+          RUBYOPT: ${{ startsWith(matrix.ruby-version, '3.4.') && '--enable=frozen-string-literal' || '' }}

.github/workflows/docker-publish.yml

@@ -0,0 +1,55 @@
+name: Docker
+
+on:
+  workflow_dispatch:
+    inputs:
+      tagInput:
+        description: 'Tag'
+        required: true
+    
+  release:
+    types: [created]
+    tags:
+      - 'v*'
+
+jobs:
+  build-and-push-image:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v3
+      -
+        name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+      -
+        name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Determine version tag
+        id: version-tag
+        run: |
+          INPUT_VALUE="${{ github.event.inputs.tagInput }}"
+          if [ -z "$INPUT_VALUE" ]; then
+            INPUT_VALUE="${{ github.ref_name }}"
+          fi
+          echo "::set-output name=value::$INPUT_VALUE"
+      -
+        name: Build and push
+        uses: docker/build-push-action@v3
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: |
+            ghcr.io/basecamp/kamal:latest
+            ghcr.io/basecamp/kamal:${{ steps.version-tag.outputs.value }}

.gitignore

@@ -1,2 +1,5 @@
 .byebug_history
 *.gem
+coverage/*
+.DS_Store
+gemfiles/*.lock

.rubocop.yml

@@ -0,0 +1,2 @@
+inherit_gem:
+  rubocop-rails-omakase: rubocop.yml

CODE_OF_CONDUCT.md

@@ -0,0 +1,41 @@
+# Contributor Code of Conduct
+
+As contributors and maintainers of the Kamal project, we pledge to create a welcoming and inclusive environment for everyone. We value the participation of each member of our community and want all contributors to feel respected and valued.
+
+We are committed to providing a harassment-free experience for everyone, regardless of gender, gender identity and expression, sexual orientation, disability, physical appearance, body size, race, age, or religion (or lack thereof). We do not tolerate harassment of participants in any form.
+
+This code of conduct applies to all Kamal project spaces, including but not limited to project code, issue trackers, chat rooms, and mailing lists. Violations of this code of conduct may result in removal from the project community.
+
+## Our standards
+
+Examples of behavior that contributes to creating a positive environment include:
+
+- Using welcoming and inclusive language
+- Being respectful of differing viewpoints and experiences
+- Gracefully accepting constructive criticism
+- Focusing on what is best for the community
+- Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+- The use of sexualized language or imagery and unwelcome sexual attention or advances
+- Trolling, insulting/derogatory comments, and personal or political attacks
+- Public or private harassment
+- Publishing others' private information, such as a physical or electronic address, without explicit permission
+- Other conduct which could reasonably be considered inappropriate in a professional setting
+
+## Responsibilities
+
+Project maintainers are responsible for clarifying the standards of acceptable behavior and are expected to take appropriate and fair corrective action in response to any instances of unacceptable behavior.
+
+Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned with this Code of Conduct, or to ban temporarily or permanently any contributor for other behaviors that they deem inappropriate, threatening, offensive, or harmful.
+
+## Reporting
+
+If you are subject to or witness unacceptable behavior, or have any other concerns, please notify a project maintainer. All reports will be kept confidential and will be reviewed and investigated promptly.
+
+We will investigate every complaint and take appropriate action. We reserve the right to remove any content that violates this Code of Conduct, or to temporarily or permanently ban any contributor for other behaviors that we deem inappropriate, threatening, offensive, or harmful.
+
+## Attribution
+
+This Code of Conduct is adapted from the Contributor Covenant, version 1.4, available at <https://www.contributor-covenant.org/version/1/4/code-of-conduct.html>.

CONTRIBUTING.md

@@ -0,0 +1,49 @@
+# Contributing to Kamal development
+
+Thank you for considering contributing to Kamal! This document outlines some guidelines for contributing to this open source project.
+
+Please make sure to review our [Code of Conduct](CODE_OF_CONDUCT.md) before contributing to Kamal.
+
+There are several ways you can contribute to the betterment of the project:
+
+- **Report an issue?** - If the issue isn’t reported, we can’t fix it. Please report any bugs, feature, and/or improvement requests on the [Kamal GitHub Issues tracker](https://github.com/basecamp/kamal/issues).
+- **Submit patches** - Do you have a new feature or a fix you'd like to share? [Submit a pull request](https://github.com/basecamp/kamal/pulls)!
+- **Write blog articles** - Are you using Kamal? We'd love to hear how you're using it with your projects. Write a tutorial and post it on your blog!
+
+## Issues
+
+If you encounter any issues with the project, please check the [existing issues](https://github.com/basecamp/kamal/issues) first to see if the issue has already been reported. If the issue hasn't been reported, please open a new issue with a clear description of the problem and steps to reproduce it.
+
+## Pull Requests
+
+Please keep the following guidelines in mind when opening a pull request:
+
+- Ensure that your code passes the project's minitests by running ./bin/test.
+- Provide a clear and detailed description of your changes.
+- Keep your changes focused on a single concern.
+- Write clean and readable code that follows the project's code style.
+- Use descriptive variable and function names.
+- Write clear and concise commit messages.
+- Add tests for your changes, if possible.
+- Ensure that your changes don't break existing functionality.
+
+#### Commit message guidelines
+
+A good commit message should describe what changed and why.
+
+## Development
+
+The `main` branch is regularly built and tested, but it is not guaranteed to be completely stable. Tags are created regularly from release branches to indicate new official, stable release versions of Kamal.
+
+Kamal is written in Ruby. You should have Ruby 3.2+ installed on your machine in order to work on Kamal. If that's already setup, run `bundle` in the root directory to install all dependencies. Then you can run `bin/test` to run all tests.
+
+1. Fork the project repository.
+2. Create a new branch for your contribution.
+3. Write your code or make the desired changes.
+4. **Ensure that your code passes the project's minitests by running ./bin/test.**
+5. Commit your changes and push them to your forked repository.
+6. [Open a pull request](https://github.com/basecamp/kamal/pulls) to the main project repository with a detailed description of your changes.
+
+## License
+
+Kamal is released under the MIT License. By contributing to this project, you agree to license your contributions under the same license.

Dockerfile

@@ -0,0 +1,38 @@
+FROM ruby:3.4-alpine
+
+# Install docker/buildx-bin
+COPY --from=docker/buildx-bin /buildx /usr/libexec/docker/cli-plugins/docker-buildx
+
+# Set the working directory to /kamal
+WORKDIR /kamal
+
+# Copy the Gemfile, Gemfile.lock into the container
+COPY Gemfile Gemfile.lock kamal.gemspec ./
+
+# Required in kamal.gemspec
+COPY lib/kamal/version.rb /kamal/lib/kamal/version.rb
+
+# Install system dependencies
+RUN apk add --no-cache build-base git docker-cli openssh-client-default yaml-dev \
+    && gem install bundler --version=2.6.5 \
+    && bundle install
+
+# Copy the rest of our application code into the container.
+# We do this after bundle install, to avoid having to run bundle
+# every time we do small fixes in the source code.
+COPY . .
+
+# Install the gem locally from the project folder
+RUN gem build kamal.gemspec && \
+    gem install ./kamal-*.gem --no-document
+
+# Set the working directory to /workdir
+WORKDIR /workdir
+
+# Tell git it's safe to access /workdir/.git even if
+# the directory is owned by a different user
+RUN git config --global --add safe.directory '*'
+
+# Set the entrypoint to run the installed binary in /workdir
+# Example:  docker run -it -v "$PWD:/workdir" kamal init
+ENTRYPOINT ["kamal"]

Gemfile

@@ -1,9 +1,8 @@
-source 'https://rubygems.org'
+source "https://rubygems.org"
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-# Specify your gem's dependencies in importmap-rails.gemspec.
 gemspec
 
-group :test do
+group :rubocop do
-  gem "byebug"
+  gem "rubocop-rails-omakase", require: false
 end

Gemfile.lock

@@ -1,84 +1,197 @@
 PATH
   remote: .
   specs:
-    mrsk (0.0.1)
+    kamal (2.7.0)
-      railties (>= 7.0.0)
+      activesupport (>= 7.0)
-      sshkit (~> 1.21)
+      base64 (~> 0.2)
+      bcrypt_pbkdf (~> 1.0)
+      concurrent-ruby (~> 1.2)
+      dotenv (~> 3.1)
+      ed25519 (~> 1.4)
+      net-ssh (~> 7.3)
+      sshkit (>= 1.23.0, < 2.0)
+      thor (~> 1.3)
+      zeitwerk (>= 2.6.18, < 3.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    actionpack (7.0.4)
+    actionpack (8.0.0.1)
-      actionview (= 7.0.4)
+      actionview (= 8.0.0.1)
-      activesupport (= 7.0.4)
+      activesupport (= 8.0.0.1)
-      rack (~> 2.0, >= 2.2.0)
+      nokogiri (>= 1.8.5)
+      rack (>= 2.2.4)
+      rack-session (>= 1.0.1)
       rack-test (>= 0.6.3)
-      rails-dom-testing (~> 2.0)
+      rails-dom-testing (~> 2.2)
-      rails-html-sanitizer (~> 1.0, >= 1.2.0)
+      rails-html-sanitizer (~> 1.6)
-    actionview (7.0.4)
+      useragent (~> 0.16)
-      activesupport (= 7.0.4)
+    actionview (8.0.0.1)
+      activesupport (= 8.0.0.1)
       builder (~> 3.1)
-      erubi (~> 1.4)
+      erubi (~> 1.11)
-      rails-dom-testing (~> 2.0)
+      rails-dom-testing (~> 2.2)
-      rails-html-sanitizer (~> 1.1, >= 1.2.0)
+      rails-html-sanitizer (~> 1.6)
-    activesupport (7.0.4)
+    activesupport (8.0.0.1)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
+      base64
+      benchmark (>= 0.3)
+      bigdecimal
+      concurrent-ruby (~> 1.0, >= 1.3.1)
+      connection_pool (>= 2.2.5)
+      drb
       i18n (>= 1.6, < 2)
+      logger (>= 1.4.2)
       minitest (>= 5.1)
-      tzinfo (~> 2.0)
+      securerandom (>= 0.3)
-    builder (3.2.4)
+      tzinfo (~> 2.0, >= 2.0.5)
-    byebug (11.1.3)
+      uri (>= 0.13.1)
-    concurrent-ruby (1.1.10)
+    ast (2.4.2)
+    base64 (0.2.0)
+    bcrypt_pbkdf (1.1.1)
+    benchmark (0.4.0)
+    bigdecimal (3.1.8)
+    builder (3.3.0)
+    concurrent-ruby (1.3.4)
+    connection_pool (2.4.1)
     crass (1.0.6)
-    erubi (1.12.0)
+    date (3.4.1)
-    i18n (1.12.0)
+    debug (1.9.2)
+      irb (~> 1.10)
+      reline (>= 0.3.8)
+    dotenv (3.1.5)
+    drb (2.2.1)
+    ed25519 (1.4.0)
+    erubi (1.13.0)
+    i18n (1.14.6)
       concurrent-ruby (~> 1.0)
-    loofah (2.19.1)
+    io-console (0.8.0)
+    irb (1.14.2)
+      rdoc (>= 4.0.0)
+      reline (>= 0.4.2)
+    json (2.9.0)
+    language_server-protocol (3.17.0.3)
+    logger (1.6.3)
+    loofah (2.23.1)
       crass (~> 1.0.2)
-      nokogiri (>= 1.5.9)
+      nokogiri (>= 1.12.0)
-    method_source (1.0.0)
+    minitest (5.25.4)
-    minitest (5.17.0)
+    mocha (2.7.1)
+      ruby2_keywords (>= 0.0.5)
     net-scp (4.0.0)
       net-ssh (>= 2.6.5, < 8.0.0)
-    net-ssh (7.0.1)
+    net-sftp (4.0.0)
-    nokogiri (1.13.10-arm64-darwin)
+      net-ssh (>= 5.0.0, < 8.0.0)
+    net-ssh (7.3.0)
+    nokogiri (1.18.9-aarch64-linux-musl)
       racc (~> 1.4)
-    racc (1.6.2)
+    nokogiri (1.18.9-arm64-darwin)
-    rack (2.2.5)
+      racc (~> 1.4)
-    rack-test (2.0.2)
+    nokogiri (1.18.9-x86_64-darwin)
+      racc (~> 1.4)
+    nokogiri (1.18.9-x86_64-linux-gnu)
+      racc (~> 1.4)
+    nokogiri (1.18.9-x86_64-linux-musl)
+      racc (~> 1.4)
+    ostruct (0.6.1)
+    parallel (1.26.3)
+    parser (3.3.6.0)
+      ast (~> 2.4.1)
+      racc
+    psych (5.2.1)
+      date
+      stringio
+    racc (1.8.1)
+    rack (3.1.16)
+    rack-session (2.1.1)
+      base64 (>= 0.1.0)
+      rack (>= 3.0.0)
+    rack-test (2.1.0)
       rack (>= 1.3)
-    rails-dom-testing (2.0.3)
+    rackup (2.2.1)
-      activesupport (>= 4.2.0)
+      rack (>= 3)
+    rails-dom-testing (2.2.0)
+      activesupport (>= 5.0.0)
+      minitest
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.4.4)
+    rails-html-sanitizer (1.6.2)
-      loofah (~> 2.19, >= 2.19.1)
+      loofah (~> 2.21)
-    railties (7.0.4)
+      nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
-      actionpack (= 7.0.4)
+    railties (8.0.0.1)
-      activesupport (= 7.0.4)
+      actionpack (= 8.0.0.1)
-      method_source
+      activesupport (= 8.0.0.1)
+      irb (~> 1.13)
+      rackup (>= 1.0.0)
       rake (>= 12.2)
-      thor (~> 1.0)
+      thor (~> 1.0, >= 1.2.2)
-      zeitwerk (~> 2.5)
+      zeitwerk (~> 2.6)
-    rake (13.0.6)
+    rainbow (3.1.1)
-    sshkit (1.21.3)
+    rake (13.2.1)
+    rdoc (6.8.1)
+      psych (>= 4.0.0)
+    regexp_parser (2.9.3)
+    reline (0.5.12)
+      io-console (~> 0.5)
+    rubocop (1.69.2)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.3.0.2)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 2.9.3, < 3.0)
+      rubocop-ast (>= 1.36.2, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 4.0)
+    rubocop-ast (1.36.2)
+      parser (>= 3.3.1.0)
+    rubocop-minitest (0.36.0)
+      rubocop (>= 1.61, < 2.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
+    rubocop-performance (1.23.0)
+      rubocop (>= 1.48.1, < 2.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
+    rubocop-rails (2.27.0)
+      activesupport (>= 4.2.0)
+      rack (>= 1.1)
+      rubocop (>= 1.52.0, < 2.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
+    rubocop-rails-omakase (1.0.0)
+      rubocop
+      rubocop-minitest
+      rubocop-performance
+      rubocop-rails
+    ruby-progressbar (1.13.0)
+    ruby2_keywords (0.0.5)
+    securerandom (0.4.0)
+    sshkit (1.23.2)
+      base64
       net-scp (>= 1.1.2)
+      net-sftp (>= 2.1.2)
       net-ssh (>= 2.8.0)
-    thor (1.2.1)
+      ostruct
-    tzinfo (2.0.5)
+    stringio (3.1.2)
+    thor (1.4.0)
+    tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    zeitwerk (2.6.6)
+    unicode-display_width (3.1.2)
+      unicode-emoji (~> 4.0, >= 4.0.4)
+    unicode-emoji (4.0.4)
+    uri (1.0.3)
+    useragent (0.16.11)
+    zeitwerk (2.7.1)
 
 PLATFORMS
-  arm64-darwin-20
+  aarch64-linux-musl
-  arm64-darwin-21
+  arm64-darwin
-  arm64-darwin-22
+  x86_64-darwin
-  x86_64-darwin-20
-  x86_64-darwin-21
   x86_64-linux
+  x86_64-linux-musl
 
 DEPENDENCIES
-  byebug
+  debug
-  mrsk!
+  kamal!
+  mocha
+  railties
+  rubocop-rails-omakase
 
 BUNDLED WITH
-   2.2.33
+   2.6.5

README.md

@@ -1,55 +1,13 @@
-# MRSK
+# Kamal: Deploy web apps anywhere
 
-MRSK lets you do zero-downtime deploys of Rails apps packed as containers to any host running Docker. It uses the dynamic reverse-proxy Traefik to hold requests while the new application container is started and the old one is wound down. It works across multiple hosts at the same time, using SSHKit to execute commands.
+From bare metal to cloud VMs, deploy web apps anywhere with zero downtime. Kamal uses [kamal-proxy](https://github.com/basecamp/kamal-proxy) to seamlessly switch requests between containers. Works seamlessly across multiple servers, using SSHKit to execute commands. Originally built for Rails apps, Kamal will work with any type of web app that can be containerized with Docker.
 
-## Installation
+➡️ See [kamal-deploy.org](https://kamal-deploy.org) for documentation on [installation](https://kamal-deploy.org/docs/installation), [configuration](https://kamal-deploy.org/docs/configuration), and [commands](https://kamal-deploy.org/docs/commands).
 
-Create a configuration file for MRSK in `config/deploy.yml` that looks like this:
+## Contributing to the documentation
 
-```yaml
+Please help us improve Kamal's documentation on the [the basecamp/kamal-site repository](https://github.com/basecamp/kamal-site).
-service: my-app
-image: name/my-app
-servers:
-  - xxx.xxx.xxx.xxx
-  - xxx.xxx.xxx.xxx
-env:
-  DATABASE_URL: mysql2://username@localhost/database_name/
-  REDIS_URL: redis://host:6379/1
-```
-
-Then first login to the Docker Hub registry on the servers:
-
-```
-rake mrsk:registry:login DOCKER_USER=name DOCKER_PASSWORD=pw
-```
-
-Now you're ready to deploy a multi-arch image (FIXME: currently you need to manually run `docker buildx create --use` once first):
-
-```
-rake mrsk:deploy
-```
-
-This will:
-
-1. Build the image using the standard Dockerfile in the root of the application.
-2. Push the image to the registry.
-3. Pull the image on all the servers.
-4. Ensure Traefik is running and accepting traffic on port 80.
-5. Stop any containers running a previous versions of the app.
-6. Start a new container with the version of the app that matches the current git version hash.
-
-Voila! All the servers are now serving the app on port 80, and you're ready to put them behind a load balancer to serve live traffic.
-
-## Stage of development
-
-This is alpha software. Lots of stuff is missing. Here are some of the areas we seek to improve:
-
-- Use of other registries than Docker Hub
-- Adapterize commands to work with Podman and other container runners
-- Better flow for secrets and ENV
-- Possibly switching to a bin/mrsk command rather than raw rake
-- Integrate wirmth cloud CI pipelines
 
 ## License
 
-Mrsk is released under the [MIT License](https://opensource.org/licenses/MIT).
+Kamal is released under the [MIT License](https://opensource.org/licenses/MIT).

bin/docs

@@ -0,0 +1,141 @@
+#!/usr/bin/env ruby
+require "stringio"
+
+def usage
+  puts "Usage: #{$0} <kamal_site_repo>"
+  exit 1
+end
+
+usage if ARGV.size != 1
+
+kamal_site_repo = ARGV[0]
+
+if !File.directory?(kamal_site_repo)
+  puts "Error: #{kamal_site_repo} is not a directory"
+  exit 1
+end
+
+DOCS = {
+  "accessory" => "Accessories",
+  "alias" => "Aliases",
+  "boot" => "Booting",
+  "builder" => "Builders",
+  "configuration" => "Configuration overview",
+  "env" => "Environment variables",
+  "logging" => "Logging",
+  "proxy" => "Proxy",
+  "registry" => "Docker Registry",
+  "role" => "Roles",
+  "servers" => "Servers",
+  "ssh" => "SSH",
+  "sshkit" => "SSHKit"
+}
+DOCS_PATH = "lib/kamal/configuration/docs"
+
+class DocWriter
+  attr_reader :from_file, :to_file, :key, :heading, :body, :output, :in_yaml
+
+  def initialize(from_file, to_dir)
+    @from_file = from_file
+    @key = File.basename(from_file, ".yml")
+    @to_file = File.join(to_dir, "#{linkify(DOCS[key])}.md")
+    @body = File.readlines(from_file)
+    @heading = body.shift.chomp("\n")
+    @output = nil
+  end
+
+  def write
+    puts "Writing #{to_file}"
+    generate_markdown
+    File.write(to_file, output.string)
+  end
+
+  private
+    def generate_markdown
+      @output = StringIO.new
+
+      generate_header
+
+      place = :in_section
+
+      loop do
+        line = body.shift&.chomp("\n")
+        break if line.nil?
+
+        case place
+        when :new_section, :in_section
+          if line.empty?
+            output.puts
+            place = :new_section
+          elsif line =~ /^ *#/
+            generate_line(line, heading: place == :new_section)
+            place = :in_section
+          else
+            output.puts
+            output.puts "```yaml"
+            output.puts line
+            place = :in_yaml
+          end
+        when :in_yaml, :in_empty_line_yaml
+          if line =~ /^ *#/
+            output.puts "```"
+            output.puts
+            generate_line(line, heading: place == :in_empty_line_yaml)
+            place = :in_section
+          elsif line.empty?
+            place = :in_empty_line_yaml
+          else
+            output.puts line
+          end
+        end
+      end
+
+      output.puts "```" if place == :in_yaml
+    end
+
+    def generate_header
+      output.puts "---"
+      output.puts "# This file has been generated from the Kamal source, do not edit directly."
+      output.puts "# Find the source of this file at #{DOCS_PATH}/#{key}.yml in the Kamal repository."
+      output.puts "title: #{heading[2..-1]}"
+      output.puts "---"
+      output.puts
+      output.puts heading
+    end
+
+    def generate_line(line, heading: false)
+      line = line.gsub(/^ *#\s?/, "")
+
+      if line =~ /(.*)kamal docs ([a-z]*)(.*)/
+        line = "#{$1}[#{DOCS[$2]}](../#{linkify(DOCS[$2])})#{$3}"
+      end
+
+      if line =~ /(.*)https:\/\/kamal-deploy.org([a-z\/-]*)(.*)/
+        line = "#{$1}[#{titlify($2.split("/").last)}](#{$2})#{$3}"
+      end
+
+      if heading
+        output.puts "## [#{line}](##{linkify(line)})"
+      else
+        output.puts line
+      end
+    end
+
+    def linkify(text)
+      if text == "Configuration overview"
+        "overview"
+      else
+        text.downcase.gsub(" ", "-")
+      end
+    end
+
+    def titlify(text)
+      text.capitalize.gsub("-", " ")
+    end
+end
+
+from_dir = File.join(File.dirname(__FILE__), "../#{DOCS_PATH}")
+to_dir = File.join(kamal_site_repo, "docs/configuration")
+Dir.glob("#{from_dir}/*") do |from_file|
+  DocWriter.new(from_file, to_dir).write
+end

bin/kamal

@@ -0,0 +1,18 @@
+#!/usr/bin/env ruby
+
+# Prevent failures from being reported twice.
+Thread.report_on_exception = false
+
+require "kamal"
+
+begin
+  Kamal::Cli::Main.start(ARGV)
+rescue SSHKit::Runner::ExecuteError => e
+  puts "  \e[31mERROR (#{e.cause.class}): #{e.message}\e[0m"
+  puts e.cause.backtrace if ENV["VERBOSE"]
+  exit 1
+rescue => e
+  puts "  \e[31mERROR (#{e.class}): #{e.message}\e[0m"
+  puts e.backtrace if ENV["VERBOSE"]
+  exit 1
+end

bin/release

@@ -2,13 +2,13 @@
 
 VERSION=$1
 
-printf "module Mrsk\n  VERSION = \"$VERSION\"\nend\n" > ./lib/mrsk/version.rb
+printf "module Kamal\n  VERSION = \"$VERSION\"\nend\n" > ./lib/kamal/version.rb
 bundle
-git add Gemfile.lock lib/mrsk/version.rb
+git add Gemfile.lock lib/kamal/version.rb
 git commit -m "Bump version for $VERSION"
 git push
 git tag v$VERSION
 git push --tags
-gem build mrsk.gemspec
+gem build kamal.gemspec
-gem push "mrsk-$VERSION.gem" --host https://rubygems.org
+gem push "kamal-$VERSION.gem" --host https://rubygems.org
-rm "mrsk-$VERSION.gem"
+rm "kamal-$VERSION.gem"

gemfiles/rails_edge.gemfile

@@ -0,0 +1,9 @@
+source 'https://rubygems.org'
+git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
+git "https://github.com/rails/rails.git" do
+  gem "railties"
+  gem "activesupport"
+end
+
+gemspec path: "../"

kamal.gemspec

@@ -0,0 +1,28 @@
+require_relative "lib/kamal/version"
+
+Gem::Specification.new do |spec|
+  spec.name        = "kamal"
+  spec.version     = Kamal::VERSION
+  spec.authors     = [ "David Heinemeier Hansson" ]
+  spec.email       = "dhh@hey.com"
+  spec.homepage    = "https://github.com/basecamp/kamal"
+  spec.summary     = "Deploy web apps in containers to servers running Docker with zero downtime."
+  spec.license     = "MIT"
+  spec.files = Dir["lib/**/*", "MIT-LICENSE", "README.md"]
+  spec.executables = %w[ kamal ]
+
+  spec.add_dependency "activesupport", ">= 7.0"
+  spec.add_dependency "sshkit", ">= 1.23.0", "< 2.0"
+  spec.add_dependency "net-ssh", "~> 7.3"
+  spec.add_dependency "thor", "~> 1.3"
+  spec.add_dependency "dotenv", "~> 3.1"
+  spec.add_dependency "zeitwerk", ">= 2.6.18", "< 3.0"
+  spec.add_dependency "ed25519", "~> 1.4"
+  spec.add_dependency "bcrypt_pbkdf", "~> 1.0"
+  spec.add_dependency "concurrent-ruby", "~> 1.2"
+  spec.add_dependency "base64", "~> 0.2"
+
+  spec.add_development_dependency "debug"
+  spec.add_development_dependency "mocha"
+  spec.add_development_dependency "railties"
+end

lib/kamal.rb

@@ -0,0 +1,14 @@
+module Kamal
+  class ConfigurationError < StandardError; end
+end
+
+require "active_support"
+require "zeitwerk"
+require "yaml"
+require "tmpdir"
+require "pathname"
+
+loader = Zeitwerk::Loader.for_gem
+loader.ignore(File.join(__dir__, "kamal", "sshkit_with_ext.rb"))
+loader.setup
+loader.eager_load_namespace(Kamal::Cli) # We need all commands loaded.

lib/kamal/cli.rb

@@ -0,0 +1,9 @@
+module Kamal::Cli
+  class BootError < StandardError; end
+  class HookError < StandardError; end
+  class LockError < StandardError; end
+  class DependencyError < StandardError; end
+end
+
+# SSHKit uses instance eval, so we need a global const for ergonomics
+KAMAL = Kamal::Commander.new

lib/kamal/cli/accessory.rb

@@ -0,0 +1,313 @@
+require "active_support/core_ext/array/conversions"
+require "concurrent/array"
+
+class Kamal::Cli::Accessory < Kamal::Cli::Base
+  desc "boot [NAME]", "Boot new accessory service on host (use NAME=all to boot all accessories)"
+  def boot(name, prepare: true)
+    with_lock do
+      if name == "all"
+        KAMAL.accessory_names.each { |accessory_name| boot(accessory_name) }
+      else
+        prepare(name) if prepare
+
+        with_accessory(name) do |accessory, hosts|
+          booted_hosts = Concurrent::Array.new
+          on(hosts) do |host|
+            booted_hosts << host.to_s if capture_with_info(*accessory.info(all: true, quiet: true)).strip.presence
+          end
+
+          if booted_hosts.any?
+            say "Skipping booting `#{name}` on #{booted_hosts.sort.join(", ")}, a container already exists", :yellow
+            hosts -= booted_hosts
+          end
+
+          directories(name)
+          upload(name)
+
+          on(hosts) do |host|
+            execute *KAMAL.auditor.record("Booted #{name} accessory"), verbosity: :debug
+            execute *accessory.ensure_env_directory
+            upload! accessory.secrets_io, accessory.secrets_path, mode: "0600"
+            execute *accessory.run(host: host)
+
+            if accessory.running_proxy?
+              target = capture_with_info(*accessory.container_id_for(container_name: accessory.service_name, only_running: true)).strip
+              execute *accessory.deploy(target: target)
+            end
+          end
+        end
+      end
+    end
+  end
+
+  desc "upload [NAME]", "Upload accessory files to host", hide: true
+  def upload(name)
+    with_lock do
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          accessory.files.each do |(local, remote)|
+            accessory.ensure_local_file_present(local)
+
+            execute *accessory.make_directory_for(remote)
+            upload! local, remote
+            execute :chmod, "755", remote
+          end
+        end
+      end
+    end
+  end
+
+  desc "directories [NAME]", "Create accessory directories on host", hide: true
+  def directories(name)
+    with_lock do
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          accessory.directories.keys.each do |host_path|
+            execute *accessory.make_directory(host_path)
+          end
+        end
+      end
+    end
+  end
+
+  desc "reboot [NAME]", "Reboot existing accessory on host (stop container, remove container, start new container; use NAME=all to boot all accessories)"
+  def reboot(name)
+    with_lock do
+      if name == "all"
+        KAMAL.accessory_names.each { |accessory_name| reboot(accessory_name) }
+      else
+        prepare(name)
+        stop(name)
+        remove_container(name)
+        boot(name, prepare: false)
+      end
+    end
+  end
+
+  desc "start [NAME]", "Start existing accessory container on host"
+  def start(name)
+    with_lock do
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          execute *KAMAL.auditor.record("Started #{name} accessory"), verbosity: :debug
+          execute *accessory.start
+          if accessory.running_proxy?
+            target = capture_with_info(*accessory.container_id_for(container_name: accessory.service_name, only_running: true)).strip
+            execute *accessory.deploy(target: target)
+          end
+        end
+      end
+    end
+  end
+
+  desc "stop [NAME]", "Stop existing accessory container on host"
+  def stop(name)
+    with_lock do
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          execute *KAMAL.auditor.record("Stopped #{name} accessory"), verbosity: :debug
+          execute *accessory.stop, raise_on_non_zero_exit: false
+
+          if accessory.running_proxy?
+            target = capture_with_info(*accessory.container_id_for(container_name: accessory.service_name, only_running: true)).strip
+            execute *accessory.remove if target
+          end
+        end
+      end
+    end
+  end
+
+  desc "restart [NAME]", "Restart existing accessory container on host"
+  def restart(name)
+    with_lock do
+      stop(name)
+      start(name)
+    end
+  end
+
+  desc "details [NAME]", "Show details about accessory on host (use NAME=all to show all accessories)"
+  def details(name)
+    if name == "all"
+      KAMAL.accessory_names.each { |accessory_name| details(accessory_name) }
+    else
+      type = "Accessory #{name}"
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) { puts_by_host host, capture_with_info(*accessory.info), type: type }
+      end
+    end
+  end
+
+  desc "exec [NAME] [CMD...]", "Execute a custom command on servers within the accessory container (use --help to show options)"
+  option :interactive, aliases: "-i", type: :boolean, default: false, desc: "Execute command over ssh for an interactive shell (use for console/bash)"
+  option :reuse, type: :boolean, default: false, desc: "Reuse currently running container instead of starting a new one"
+  def exec(name, *cmd)
+    pre_connect_if_required
+
+    cmd = Kamal::Utils.join_commands(cmd)
+    with_accessory(name) do |accessory, hosts|
+      case
+      when options[:interactive] && options[:reuse]
+        say "Launching interactive command via SSH from existing container...", :magenta
+        run_locally { exec accessory.execute_in_existing_container_over_ssh(cmd) }
+
+      when options[:interactive]
+        say "Launching interactive command via SSH from new container...", :magenta
+        on(accessory.hosts.first) { execute *KAMAL.registry.login }
+        run_locally { exec accessory.execute_in_new_container_over_ssh(cmd) }
+
+      when options[:reuse]
+        say "Launching command from existing container...", :magenta
+        on(hosts) do |host|
+          execute *KAMAL.auditor.record("Executed cmd '#{cmd}' on #{name} accessory"), verbosity: :debug
+          puts_by_host host, capture_with_info(*accessory.execute_in_existing_container(cmd))
+        end
+
+      else
+        say "Launching command from new container...", :magenta
+        on(hosts) do |host|
+          execute *KAMAL.registry.login
+          execute *KAMAL.auditor.record("Executed cmd '#{cmd}' on #{name} accessory"), verbosity: :debug
+          puts_by_host host, capture_with_info(*accessory.execute_in_new_container(cmd))
+        end
+      end
+    end
+  end
+
+  desc "logs [NAME]", "Show log lines from accessory on host (use --help to show options)"
+  option :since, aliases: "-s", desc: "Show logs since timestamp (e.g. 2013-01-02T13:23:37Z) or relative (e.g. 42m for 42 minutes)"
+  option :lines, type: :numeric, aliases: "-n", desc: "Number of log lines to pull from each server"
+  option :grep, aliases: "-g", desc: "Show lines with grep match only (use this to fetch specific requests by id)"
+  option :grep_options, desc: "Additional options supplied to grep"
+  option :follow, aliases: "-f", desc: "Follow logs on primary server (or specific host set by --hosts)"
+  option :skip_timestamps, type: :boolean, aliases: "-T", desc: "Skip appending timestamps to logging output"
+  def logs(name)
+    with_accessory(name) do |accessory, hosts|
+      grep = options[:grep]
+      grep_options = options[:grep_options]
+      timestamps = !options[:skip_timestamps]
+
+      if options[:follow]
+        run_locally do
+          info "Following logs on #{hosts}..."
+          info accessory.follow_logs(timestamps: timestamps, grep: grep, grep_options: grep_options)
+          exec accessory.follow_logs(timestamps: timestamps, grep: grep, grep_options: grep_options)
+        end
+      else
+        since = options[:since]
+        lines = options[:lines].presence || ((since || grep) ? nil : 100) # Default to 100 lines if since or grep isn't set
+
+        on(hosts) do
+          puts capture_with_info(*accessory.logs(timestamps: timestamps, since: since, lines: lines, grep: grep, grep_options: grep_options))
+        end
+      end
+    end
+  end
+
+  desc "remove [NAME]", "Remove accessory container, image and data directory from host (use NAME=all to remove all accessories)"
+  option :confirmed, aliases: "-y", type: :boolean, default: false, desc: "Proceed without confirmation question"
+  def remove(name)
+    confirming "This will remove all containers, images and data directories for #{name}. Are you sure?" do
+      with_lock do
+        if name == "all"
+          KAMAL.accessory_names.each { |accessory_name| remove_accessory(accessory_name) }
+        else
+          remove_accessory(name)
+        end
+      end
+    end
+  end
+
+  desc "remove_container [NAME]", "Remove accessory container from host", hide: true
+  def remove_container(name)
+    with_lock do
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          execute *KAMAL.auditor.record("Remove #{name} accessory container"), verbosity: :debug
+          execute *accessory.remove_container
+        end
+      end
+    end
+  end
+
+  desc "remove_image [NAME]", "Remove accessory image from host", hide: true
+  def remove_image(name)
+    with_lock do
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          execute *KAMAL.auditor.record("Removed #{name} accessory image"), verbosity: :debug
+          execute *accessory.remove_image
+        end
+      end
+    end
+  end
+
+  desc "remove_service_directory [NAME]", "Remove accessory directory used for uploaded files and data directories from host", hide: true
+  def remove_service_directory(name)
+    with_lock do
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          execute *accessory.remove_service_directory
+        end
+      end
+    end
+  end
+
+  desc "upgrade", "Upgrade accessories from Kamal 1.x to 2.0 (restart them in 'kamal' network)"
+  option :rolling, type: :boolean, default: false, desc: "Upgrade one host at a time"
+  option :confirmed, aliases: "-y", type: :boolean, default: false, desc: "Proceed without confirmation question"
+  def upgrade(name)
+    confirming "This will restart all accessories" do
+      with_lock do
+        host_groups = options[:rolling] ? KAMAL.accessory_hosts : [ KAMAL.accessory_hosts ]
+        host_groups.each do |hosts|
+          host_list = Array(hosts).join(",")
+          KAMAL.with_specific_hosts(hosts) do
+            say "Upgrading #{name} accessories on #{host_list}...", :magenta
+            reboot name
+            say "Upgraded #{name} accessories on #{host_list}...", :magenta
+          end
+        end
+      end
+    end
+  end
+
+  private
+    def with_accessory(name)
+      if KAMAL.config.accessory(name)
+        accessory = KAMAL.accessory(name)
+        yield accessory, accessory_hosts(accessory)
+      else
+        error_on_missing_accessory(name)
+      end
+    end
+
+    def error_on_missing_accessory(name)
+      options = KAMAL.accessory_names.presence
+
+      error \
+        "No accessory by the name of '#{name}'" +
+        (options ? " (options: #{options.to_sentence})" : "")
+    end
+
+    def accessory_hosts(accessory)
+      KAMAL.accessory_hosts & accessory.hosts
+    end
+
+    def remove_accessory(name)
+      stop(name)
+      remove_container(name)
+      remove_image(name)
+      remove_service_directory(name)
+    end
+
+    def prepare(name)
+      with_accessory(name) do |accessory, hosts|
+        on(hosts) do
+          execute *KAMAL.registry.login(registry_config: accessory.registry)
+          execute *KAMAL.docker.create_network
+        rescue SSHKit::Command::Failed => e
+          raise unless e.message.include?("already exists")
+        end
+      end
+    end
+end

lib/kamal/cli/alias/command.rb

@@ -0,0 +1,10 @@
+class Kamal::Cli::Alias::Command < Thor::DynamicCommand
+  def run(instance, args = [])
+    if (_alias = KAMAL.config.aliases[name])
+      KAMAL.reset
+      Kamal::Cli::Main.start(Shellwords.split(_alias.command) + ARGV[1..-1])
+    else
+      super
+    end
+  end
+end

lib/kamal/cli/app.rb

@@ -0,0 +1,400 @@
+class Kamal::Cli::App < Kamal::Cli::Base
+  desc "boot", "Boot app on servers (or reboot app if already running)"
+  def boot
+    with_lock do
+      say "Get most recent version available as an image...", :magenta unless options[:version]
+      using_version(version_or_latest) do |version|
+        say "Start container with version #{version} (or reboot if already running)...", :magenta
+
+        # Assets are prepared in a separate step to ensure they are on all hosts before booting
+        on(KAMAL.app_hosts) do
+          Kamal::Cli::App::ErrorPages.new(host, self).run
+
+          KAMAL.roles_on(host).each do |role|
+            Kamal::Cli::App::Assets.new(host, role, self).run
+            Kamal::Cli::App::SslCertificates.new(host, role, self).run
+          end
+        end
+
+        # Primary hosts and roles are returned first, so they can open the barrier
+        barrier = Kamal::Cli::Healthcheck::Barrier.new
+
+        host_boot_groups.each do |hosts|
+          host_list = Array(hosts).join(",")
+          run_hook "pre-app-boot", hosts: host_list
+
+          on(hosts) do |host|
+            KAMAL.roles_on(host).each do |role|
+              Kamal::Cli::App::Boot.new(host, role, self, version, barrier).run
+            end
+          end
+
+          run_hook "post-app-boot", hosts: host_list
+          sleep KAMAL.config.boot.wait if KAMAL.config.boot.wait
+        end
+
+        # Tag once the app booted on all hosts
+        on(KAMAL.app_hosts) do |host|
+          execute *KAMAL.auditor.record("Tagging #{KAMAL.config.absolute_image} as the latest image"), verbosity: :debug
+          execute *KAMAL.app.tag_latest_image
+        end
+      end
+    end
+  end
+
+  desc "start", "Start existing app container on servers"
+  def start
+    with_lock do
+      on(KAMAL.app_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          app = KAMAL.app(role: role, host: host)
+          execute *KAMAL.auditor.record("Started app version #{KAMAL.config.version}"), verbosity: :debug
+          execute *app.start, raise_on_non_zero_exit: false
+
+          if role.running_proxy?
+            version = capture_with_info(*app.current_running_version, raise_on_non_zero_exit: false).strip
+            endpoint = capture_with_info(*app.container_id_for_version(version)).strip
+            raise Kamal::Cli::BootError, "Failed to get endpoint for #{role} on #{host}, did the container boot?" if endpoint.empty?
+
+            execute *app.deploy(target: endpoint)
+          end
+        end
+      end
+    end
+  end
+
+  desc "stop", "Stop app container on servers"
+  def stop
+    with_lock do
+      on(KAMAL.app_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          app = KAMAL.app(role: role, host: host)
+          execute *KAMAL.auditor.record("Stopped app", role: role), verbosity: :debug
+
+          if role.running_proxy?
+            version = capture_with_info(*app.current_running_version, raise_on_non_zero_exit: false).strip
+            endpoint = capture_with_info(*app.container_id_for_version(version)).strip
+            if endpoint.present?
+              execute *app.remove, raise_on_non_zero_exit: false
+            end
+          end
+
+          execute *app.stop, raise_on_non_zero_exit: false
+        end
+      end
+    end
+  end
+
+  # FIXME: Drop in favor of just containers?
+  desc "details", "Show details about app containers"
+  def details
+    on(KAMAL.app_hosts) do |host|
+      roles = KAMAL.roles_on(host)
+
+      roles.each do |role|
+        puts_by_host host, capture_with_info(*KAMAL.app(role: role, host: host).info)
+      end
+    end
+  end
+
+  desc "exec [CMD...]", "Execute a custom command on servers within the app container (use --help to show options)"
+  option :interactive, aliases: "-i", type: :boolean, default: false, desc: "Execute command over ssh for an interactive shell (use for console/bash)"
+  option :reuse, type: :boolean, default: false, desc: "Reuse currently running container instead of starting a new one"
+  option :env, aliases: "-e", type: :hash, desc: "Set environment variables for the command"
+  option :detach, type: :boolean, default: false, desc: "Execute command in a detached container"
+  def exec(*cmd)
+    pre_connect_if_required
+
+    if (incompatible_options = [ :interactive, :reuse ].select { |key| options[:detach] && options[key] }.presence)
+      raise ArgumentError, "Detach is not compatible with #{incompatible_options.join(" or ")}"
+    end
+
+    if cmd.empty?
+      raise ArgumentError, "No command provided. You must specify a command to execute."
+    end
+
+    cmd = Kamal::Utils.join_commands(cmd)
+    env = options[:env]
+    detach = options[:detach]
+    case
+    when options[:interactive] && options[:reuse]
+      say "Get current version of running container...", :magenta unless options[:version]
+      using_version(options[:version] || current_running_version) do |version|
+        say "Launching interactive command with version #{version} via SSH from existing container on #{KAMAL.primary_host}...", :magenta
+        run_locally { exec KAMAL.app(role: KAMAL.primary_role, host: KAMAL.primary_host).execute_in_existing_container_over_ssh(cmd, env: env) }
+      end
+
+    when options[:interactive]
+      say "Get most recent version available as an image...", :magenta unless options[:version]
+      using_version(version_or_latest) do |version|
+        say "Launching interactive command with version #{version} via SSH from new container on #{KAMAL.primary_host}...", :magenta
+        on(KAMAL.primary_host) { execute *KAMAL.registry.login }
+        run_locally do
+          exec KAMAL.app(role: KAMAL.primary_role, host: KAMAL.primary_host).execute_in_new_container_over_ssh(cmd, env: env)
+        end
+      end
+
+    when options[:reuse]
+      say "Get current version of running container...", :magenta unless options[:version]
+      using_version(options[:version] || current_running_version) do |version|
+        say "Launching command with version #{version} from existing container...", :magenta
+
+        on(KAMAL.app_hosts) do |host|
+          roles = KAMAL.roles_on(host)
+
+          roles.each do |role|
+            execute *KAMAL.auditor.record("Executed cmd '#{cmd}' on app version #{version}", role: role), verbosity: :debug
+            puts_by_host host, capture_with_info(*KAMAL.app(role: role, host: host).execute_in_existing_container(cmd, env: env))
+          end
+        end
+      end
+
+    else
+      say "Get most recent version available as an image...", :magenta unless options[:version]
+      using_version(version_or_latest) do |version|
+        say "Launching command with version #{version} from new container...", :magenta
+        on(KAMAL.app_hosts) do |host|
+          execute *KAMAL.registry.login
+
+          roles = KAMAL.roles_on(host)
+
+          roles.each do |role|
+            execute *KAMAL.auditor.record("Executed cmd '#{cmd}' on app version #{version}"), verbosity: :debug
+            puts_by_host host, capture_with_info(*KAMAL.app(role: role, host: host).execute_in_new_container(cmd, env: env, detach: detach))
+          end
+        end
+      end
+    end
+  end
+
+  desc "containers", "Show app containers on servers"
+  def containers
+    on(KAMAL.app_hosts) { |host| puts_by_host host, capture_with_info(*KAMAL.app.list_containers) }
+  end
+
+  desc "stale_containers", "Detect app stale containers"
+  option :stop, aliases: "-s", type: :boolean, default: false, desc: "Stop the stale containers found"
+  def stale_containers
+    stop = options[:stop]
+
+    with_lock_if_stopping do
+      on(KAMAL.app_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          app = KAMAL.app(role: role, host: host)
+          versions = capture_with_info(*app.list_versions, raise_on_non_zero_exit: false).split("\n")
+          versions -= [ capture_with_info(*app.current_running_version, raise_on_non_zero_exit: false).strip ]
+
+          versions.each do |version|
+            if stop
+              puts_by_host host, "Stopping stale container for role #{role} with version #{version}"
+              execute *app.stop(version: version), raise_on_non_zero_exit: false
+            else
+              puts_by_host host,  "Detected stale container for role #{role} with version #{version} (use `kamal app stale_containers --stop` to stop)"
+            end
+          end
+        end
+      end
+    end
+  end
+
+  desc "images", "Show app images on servers"
+  def images
+    on(KAMAL.app_hosts) { |host| puts_by_host host, capture_with_info(*KAMAL.app.list_images) }
+  end
+
+  desc "logs", "Show log lines from app on servers (use --help to show options)"
+  option :since, aliases: "-s", desc: "Show lines since timestamp (e.g. 2013-01-02T13:23:37Z) or relative (e.g. 42m for 42 minutes)"
+  option :lines, type: :numeric, aliases: "-n", desc: "Number of lines to show from each server"
+  option :grep, aliases: "-g", desc: "Show lines with grep match only (use this to fetch specific requests by id)"
+  option :grep_options, desc: "Additional options supplied to grep"
+  option :follow, aliases: "-f", desc: "Follow log on primary server (or specific host set by --hosts)"
+  option :skip_timestamps, type: :boolean, aliases: "-T", desc: "Skip appending timestamps to logging output"
+  option :container_id, desc: "Docker container ID to fetch logs"
+  def logs
+    # FIXME: Catch when app containers aren't running
+
+    grep = options[:grep]
+    grep_options = options[:grep_options]
+    since = options[:since]
+    container_id = options[:container_id]
+    timestamps = !options[:skip_timestamps]
+
+    if options[:follow]
+      lines = options[:lines].presence || ((since || grep) ? nil : 10) # Default to 10 lines if since or grep isn't set
+
+      run_locally do
+        info "Following logs on #{KAMAL.primary_host}..."
+
+        KAMAL.specific_roles ||= [ KAMAL.primary_role.name ]
+        role = KAMAL.roles_on(KAMAL.primary_host).first
+
+        app = KAMAL.app(role: role, host: host)
+        info app.follow_logs(host: KAMAL.primary_host, container_id: container_id, timestamps: timestamps, lines: lines, grep: grep, grep_options: grep_options)
+        exec app.follow_logs(host: KAMAL.primary_host, container_id: container_id, timestamps: timestamps, lines: lines, grep: grep, grep_options: grep_options)
+      end
+    else
+      lines = options[:lines].presence || ((since || grep) ? nil : 100) # Default to 100 lines if since or grep isn't set
+
+      on(KAMAL.app_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          begin
+            puts_by_host host, capture_with_info(*KAMAL.app(role: role, host: host).logs(container_id: container_id, timestamps: timestamps, since: since, lines: lines, grep: grep, grep_options: grep_options))
+          rescue SSHKit::Command::Failed
+            puts_by_host host, "Nothing found"
+          end
+        end
+      end
+    end
+  end
+
+  desc "remove", "Remove app containers and images from servers"
+  def remove
+    with_lock do
+      stop
+      remove_containers
+      remove_images
+      remove_app_directories
+    end
+  end
+
+  desc "live", "Set the app to live mode"
+  def live
+    with_lock do
+      on(KAMAL.proxy_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          execute *KAMAL.app(role: role, host: host).live if role.running_proxy?
+        end
+      end
+    end
+  end
+
+  desc "maintenance", "Set the app to maintenance mode"
+  option :drain_timeout, type: :numeric, desc: "How long to allow in-flight requests to complete (defaults to drain_timeout from config)"
+  option :message, type: :string, desc: "Message to display to clients while stopped"
+  def maintenance
+    maintenance_options = { drain_timeout: options[:drain_timeout] || KAMAL.config.drain_timeout, message: options[:message] }
+
+    with_lock do
+      on(KAMAL.proxy_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          execute *KAMAL.app(role: role, host: host).maintenance(**maintenance_options) if role.running_proxy?
+        end
+      end
+    end
+  end
+
+  desc "remove_container [VERSION]", "Remove app container with given version from servers", hide: true
+  def remove_container(version)
+    with_lock do
+      on(KAMAL.app_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          execute *KAMAL.auditor.record("Removed app container with version #{version}", role: role), verbosity: :debug
+          execute *KAMAL.app(role: role, host: host).remove_container(version: version)
+        end
+      end
+    end
+  end
+
+  desc "remove_containers", "Remove all app containers from servers", hide: true
+  def remove_containers
+    with_lock do
+      on(KAMAL.app_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          execute *KAMAL.auditor.record("Removed all app containers", role: role), verbosity: :debug
+          execute *KAMAL.app(role: role, host: host).remove_containers
+        end
+      end
+    end
+  end
+
+  desc "remove_images", "Remove all app images from servers", hide: true
+  def remove_images
+    with_lock do
+      on(KAMAL.app_hosts) do
+        execute *KAMAL.auditor.record("Removed all app images"), verbosity: :debug
+        execute *KAMAL.app.remove_images
+      end
+    end
+  end
+
+  desc "remove_app_directories", "Remove the app directories from servers", hide: true
+  def remove_app_directories
+    with_lock do
+      on(KAMAL.app_hosts) do |host|
+        roles = KAMAL.roles_on(host)
+
+        roles.each do |role|
+          execute *KAMAL.auditor.record("Removed #{KAMAL.config.app_directory}", role: role), verbosity: :debug
+          execute *KAMAL.server.remove_app_directory, raise_on_non_zero_exit: false
+        end
+
+        execute *KAMAL.auditor.record("Removed #{KAMAL.config.app_directory}"), verbosity: :debug
+        execute *KAMAL.app.remove_proxy_app_directory, raise_on_non_zero_exit: false
+      end
+    end
+  end
+
+  desc "version", "Show app version currently running on servers"
+  def version
+    on(KAMAL.app_hosts) do |host|
+      role = KAMAL.roles_on(host).first
+      puts_by_host host, capture_with_info(*KAMAL.app(role: role, host: host).current_running_version).strip
+    end
+  end
+
+  private
+    def using_version(new_version)
+      if new_version
+        begin
+          old_version = KAMAL.config.version
+          KAMAL.config.version = new_version
+          yield new_version
+        ensure
+          KAMAL.config.version = old_version
+        end
+      else
+        yield KAMAL.config.version
+      end
+    end
+
+    def current_running_version(host: KAMAL.primary_host)
+      version = nil
+      on(host) do
+        role = KAMAL.roles_on(host).first
+        version = capture_with_info(*KAMAL.app(role: role, host: host).current_running_version).strip
+      end
+      version.presence
+    end
+
+    def version_or_latest
+      options[:version] || KAMAL.config.latest_tag
+    end
+
+    def with_lock_if_stopping
+      if options[:stop]
+        with_lock { yield }
+      else
+        yield
+      end
+    end
+
+    def host_boot_groups
+      KAMAL.config.boot.limit ? KAMAL.app_hosts.each_slice(KAMAL.config.boot.limit).to_a : [ KAMAL.app_hosts ]
+    end
+end

lib/kamal/cli/app/assets.rb

@@ -0,0 +1,24 @@
+class Kamal::Cli::App::Assets
+  attr_reader :host, :role, :sshkit
+  delegate :execute, :capture_with_info, :info, to: :sshkit
+  delegate :assets?, to: :role
+
+  def initialize(host, role, sshkit)
+    @host = host
+    @role = role
+    @sshkit = sshkit
+  end
+
+  def run
+    if assets?
+      execute *app.extract_assets
+      old_version = capture_with_info(*app.current_running_version, raise_on_non_zero_exit: false).strip
+      execute *app.sync_asset_volumes(old_version: old_version)
+    end
+  end
+
+  private
+    def app
+      @app ||= KAMAL.app(role: role, host: host)
+    end
+end

lib/kamal/cli/app/boot.rb

@@ -0,0 +1,126 @@
+class Kamal::Cli::App::Boot
+  attr_reader :host, :role, :version, :barrier, :sshkit
+  delegate :execute, :capture_with_info, :capture_with_pretty_json, :info, :error, :upload!, to: :sshkit
+  delegate :assets?, :running_proxy?, to: :role
+
+  def initialize(host, role, sshkit, version, barrier)
+    @host = host
+    @role = role
+    @version = version
+    @barrier = barrier
+    @sshkit = sshkit
+  end
+
+  def run
+    old_version = old_version_renamed_if_clashing
+
+    wait_at_barrier if queuer?
+
+    begin
+      start_new_version
+    rescue => e
+      close_barrier if gatekeeper?
+      stop_new_version
+      raise
+    end
+
+    release_barrier if gatekeeper?
+
+    if old_version
+      stop_old_version(old_version)
+    end
+  end
+
+  private
+    def old_version_renamed_if_clashing
+      if capture_with_info(*app.container_id_for_version(version), raise_on_non_zero_exit: false).present?
+        renamed_version = "#{version}_replaced_#{SecureRandom.hex(8)}"
+        info "Renaming container #{version} to #{renamed_version} as already deployed on #{host}"
+        audit("Renaming container #{version} to #{renamed_version}")
+        execute *app.rename_container(version: version, new_version: renamed_version)
+      end
+
+      capture_with_info(*app.current_running_version, raise_on_non_zero_exit: false).strip.presence
+    end
+
+    def start_new_version
+      audit "Booted app version #{version}"
+      hostname = "#{host.to_s[0...51].chomp(".")}-#{SecureRandom.hex(6)}"
+
+      execute *app.ensure_env_directory
+      upload! role.secrets_io(host), role.secrets_path, mode: "0600"
+
+      execute *app.run(hostname: hostname)
+      if running_proxy?
+        endpoint = capture_with_info(*app.container_id_for_version(version)).strip
+        raise Kamal::Cli::BootError, "Failed to get endpoint for #{role} on #{host}, did the container boot?" if endpoint.empty?
+        execute *app.deploy(target: endpoint)
+      else
+        Kamal::Cli::Healthcheck::Poller.wait_for_healthy(pause_after_ready: true) { capture_with_info(*app.status(version: version)) }
+      end
+    rescue => e
+      error "Failed to boot #{role} on #{host}"
+      raise e
+    end
+
+    def stop_new_version
+      execute *app.stop(version: version), raise_on_non_zero_exit: false
+    end
+
+    def stop_old_version(version)
+      execute *app.stop(version: version), raise_on_non_zero_exit: false
+      execute *app.clean_up_assets if assets?
+      execute *app.clean_up_error_pages if KAMAL.config.error_pages_path
+    end
+
+    def release_barrier
+      if barrier.open
+        info "First #{KAMAL.primary_role} container is healthy on #{host}, booting any other roles"
+      end
+    end
+
+    def wait_at_barrier
+      info "Waiting for the first healthy #{KAMAL.primary_role} container before booting #{role} on #{host}..."
+      barrier.wait
+      info "First #{KAMAL.primary_role} container is healthy, booting #{role} on #{host}..."
+    rescue Kamal::Cli::Healthcheck::Error
+      info "First #{KAMAL.primary_role} container is unhealthy, not booting #{role} on #{host}"
+      raise
+    end
+
+    def close_barrier
+      if barrier.close
+        info "First #{KAMAL.primary_role} container is unhealthy on #{host}, not booting any other roles"
+        begin
+          error capture_with_info(*app.logs(container_id: app.container_id_for_version(version)))
+          error capture_with_info(*app.container_health_log(version: version))
+        rescue SSHKit::Command::Failed
+          error "Could not fetch logs for #{version}"
+        end
+      end
+    end
+
+    def barrier_role?
+      role == KAMAL.primary_role
+    end
+
+    def app
+      @app ||= KAMAL.app(role: role, host: host)
+    end
+
+    def auditor
+      @auditor = KAMAL.auditor(role: role)
+    end
+
+    def audit(message)
+      execute *auditor.record(message), verbosity: :debug
+    end
+
+    def gatekeeper?
+      barrier && barrier_role?
+    end
+
+    def queuer?
+      barrier && !barrier_role?
+    end
+end

lib/kamal/cli/app/error_pages.rb

@@ -0,0 +1,33 @@
+class Kamal::Cli::App::ErrorPages
+  ERROR_PAGES_GLOB = "{4??.html,5??.html}"
+
+  attr_reader :host, :sshkit
+  delegate :upload!, :execute, to: :sshkit
+
+  def initialize(host, sshkit)
+    @host = host
+    @sshkit = sshkit
+  end
+
+  def run
+    if KAMAL.config.error_pages_path
+      with_error_pages_tmpdir do |local_error_pages_dir|
+        execute *KAMAL.app.create_error_pages_directory
+        upload! local_error_pages_dir, KAMAL.config.proxy_boot.error_pages_directory, mode: "0700", recursive: true
+      end
+    end
+  end
+
+  private
+    def with_error_pages_tmpdir
+      Dir.mktmpdir("kamal-error-pages") do |tmpdir|
+        error_pages_dir = File.join(tmpdir, KAMAL.config.version)
+        FileUtils.mkdir(error_pages_dir)
+
+        if (files = Dir[File.join(KAMAL.config.error_pages_path, ERROR_PAGES_GLOB)]).any?
+          FileUtils.cp(files, error_pages_dir)
+          yield error_pages_dir
+        end
+      end
+    end
+end

lib/kamal/cli/app/ssl_certificates.rb

@@ -0,0 +1,28 @@
+class Kamal::Cli::App::SslCertificates
+  attr_reader :host, :role, :sshkit
+  delegate :execute, :info, :upload!, to: :sshkit
+
+  def initialize(host, role, sshkit)
+    @host = host
+    @role = role
+    @sshkit = sshkit
+  end
+
+  def run
+    if role.running_proxy? && role.proxy.custom_ssl_certificate?
+      info "Writing SSL certificates for #{role.name} on #{host}"
+      execute *app.create_ssl_directory
+      if cert_content = role.proxy.certificate_pem_content
+        upload!(StringIO.new(cert_content), role.proxy.host_tls_cert, mode: "0644")
+      end
+      if key_content = role.proxy.private_key_pem_content
+        upload!(StringIO.new(key_content), role.proxy.host_tls_key, mode: "0644")
+      end
+    end
+  end
+
+  private
+    def app
+      @app ||= KAMAL.app(role: role, host: host)
+    end
+end

lib/kamal/cli/base.rb

@@ -0,0 +1,223 @@
+require "thor"
+require "kamal/sshkit_with_ext"
+
+module Kamal::Cli
+  class Base < Thor
+    include SSHKit::DSL
+
+    def self.exit_on_failure?() true end
+    def self.dynamic_command_class() Kamal::Cli::Alias::Command end
+
+    class_option :verbose, type: :boolean, aliases: "-v", desc: "Detailed logging"
+    class_option :quiet, type: :boolean, aliases: "-q", desc: "Minimal logging"
+
+    class_option :version, desc: "Run commands against a specific app version"
+
+    class_option :primary, type: :boolean, aliases: "-p", desc: "Run commands only on primary host instead of all"
+    class_option :hosts, aliases: "-h", desc: "Run commands on these hosts instead of all (separate by comma, supports wildcards with *)"
+    class_option :roles, aliases: "-r", desc: "Run commands on these roles instead of all (separate by comma, supports wildcards with *)"
+
+    class_option :config_file, aliases: "-c", default: "config/deploy.yml", desc: "Path to config file"
+    class_option :destination, aliases: "-d", desc: "Specify destination to be used for config file (staging -> deploy.staging.yml)"
+
+    class_option :skip_hooks, aliases: "-H", type: :boolean, default: false, desc: "Don't run hooks"
+
+    def initialize(args = [], local_options = {}, config = {})
+      if config[:current_command].is_a?(Kamal::Cli::Alias::Command)
+        # When Thor generates a dynamic command, it doesn't attempt to parse the arguments.
+        # For our purposes, it means the arguments are passed in args rather than local_options.
+        super([], args, config)
+      else
+        super
+      end
+
+      initialize_commander unless KAMAL.configured?
+    end
+
+    private
+      def options_with_subcommand_class_options
+        options.merge(@_initializer.last[:class_options] || {})
+      end
+
+      def initialize_commander
+        KAMAL.tap do |commander|
+          if options[:verbose]
+            ENV["VERBOSE"] = "1" # For backtraces via cli/start
+            commander.verbosity = :debug
+          end
+
+          if options[:quiet]
+            commander.verbosity = :error
+          end
+
+          commander.configure \
+            config_file: Pathname.new(File.expand_path(options[:config_file])),
+            destination: options[:destination],
+            version: options[:version]
+
+          commander.specific_hosts    = options[:hosts]&.split(",")
+          commander.specific_roles    = options[:roles]&.split(",")
+          commander.specific_primary! if options[:primary]
+        end
+      end
+
+      def print_runtime
+        started_at = Time.now
+        yield
+        Time.now - started_at
+      ensure
+        runtime = Time.now - started_at
+        puts "  Finished all in #{sprintf("%.1f seconds", runtime)}"
+      end
+
+      def with_lock
+        if KAMAL.holding_lock?
+          yield
+        else
+          acquire_lock
+
+          begin
+            yield
+          rescue
+            begin
+              release_lock
+            rescue => e
+              say "Error releasing the deploy lock: #{e.message}", :red
+            end
+            raise
+          end
+
+          release_lock
+        end
+      end
+
+      def confirming(question)
+        return yield if options[:confirmed]
+
+        if ask(question, limited_to: %w[ y N ], default: "N") == "y"
+          yield
+        else
+          say "Aborted", :red
+        end
+      end
+
+      def acquire_lock
+        ensure_run_directory
+
+        raise_if_locked do
+          say "Acquiring the deploy lock...", :magenta
+          on(KAMAL.primary_host) { execute *KAMAL.lock.acquire("Automatic deploy lock", KAMAL.config.version), verbosity: :debug }
+        end
+
+        KAMAL.holding_lock = true
+      end
+
+      def release_lock
+        say "Releasing the deploy lock...", :magenta
+        on(KAMAL.primary_host) { execute *KAMAL.lock.release, verbosity: :debug }
+
+        KAMAL.holding_lock = false
+      end
+
+      def raise_if_locked
+        yield
+      rescue SSHKit::Runner::ExecuteError => e
+        if e.message =~ /cannot create directory/
+          say "Deploy lock already in place!", :red
+          on(KAMAL.primary_host) { puts capture_with_debug(*KAMAL.lock.status) }
+          raise LockError, "Deploy lock found. Run 'kamal lock help' for more information"
+        else
+          raise e
+        end
+      end
+
+      def run_hook(hook, **extra_details)
+        if !options[:skip_hooks] && KAMAL.hook.hook_exists?(hook)
+          details = {
+            hosts: KAMAL.hosts.join(","),
+            roles: KAMAL.specific_roles&.join(","),
+            lock: KAMAL.holding_lock?.to_s,
+            command: command,
+            subcommand: subcommand
+          }.compact
+
+          say "Running the #{hook} hook...", :magenta
+          with_env KAMAL.hook.env(**details, **extra_details) do
+            run_locally do
+              execute *KAMAL.hook.run(hook)
+            end
+          rescue SSHKit::Command::Failed => e
+            raise HookError.new("Hook `#{hook}` failed:\n#{e.message}")
+          end
+        end
+      end
+
+      def on(*args, &block)
+        pre_connect_if_required
+
+        super
+      end
+
+      def pre_connect_if_required
+        if !KAMAL.connected?
+          run_hook "pre-connect"
+          KAMAL.connected = true
+        end
+      end
+
+      def command
+        @kamal_command ||= begin
+          invocation_class, invocation_commands = *first_invocation
+          if invocation_class == Kamal::Cli::Main
+            invocation_commands[0]
+          else
+            Kamal::Cli::Main.subcommand_classes.find { |command, clazz| clazz == invocation_class }[0]
+          end
+        end
+      end
+
+      def subcommand
+        @kamal_subcommand ||= begin
+          invocation_class, invocation_commands = *first_invocation
+          invocation_commands[0] if invocation_class != Kamal::Cli::Main
+        end
+      end
+
+      def first_invocation
+        instance_variable_get("@_invocations").first
+      end
+
+      def reset_invocation(cli_class)
+        instance_variable_get("@_invocations")[cli_class].pop
+      end
+
+      def ensure_run_directory
+        on(KAMAL.hosts) do
+          execute(*KAMAL.server.ensure_run_directory)
+        end
+      end
+
+      def with_env(env)
+        current_env = ENV.to_h.dup
+        ENV.update(env)
+        yield
+      ensure
+        ENV.clear
+        ENV.update(current_env)
+      end
+
+      def ensure_docker_installed
+        run_locally do
+          begin
+            execute *KAMAL.builder.ensure_docker_installed
+          rescue SSHKit::Command::Failed => e
+            error = e.message =~ /command not found/ ?
+              "Docker is not installed locally" :
+              "Docker buildx plugin is not installed locally"
+
+            raise DependencyError, error
+          end
+        end
+      end
+  end
+end

lib/kamal/cli/build.rb

@@ -0,0 +1,204 @@
+require "uri"
+
+class Kamal::Cli::Build < Kamal::Cli::Base
+  class BuildError < StandardError; end
+
+  desc "deliver", "Build app and push app image to registry then pull image on servers"
+  def deliver
+    invoke :push
+    invoke :pull
+  end
+
+  desc "push", "Build and push app image to registry"
+  option :output, type: :string, default: "registry", banner: "export_type", desc: "Exported type for the build result, and may be any exported type supported by 'buildx --output'."
+  def push
+    cli = self
+
+    # Ensure pre-connect hooks run before the build, they may needed for a remote builder
+    # or the pre-build hooks.
+    pre_connect_if_required
+
+    ensure_docker_installed
+    login_to_registry_locally
+
+    run_hook "pre-build"
+
+    uncommitted_changes = Kamal::Git.uncommitted_changes
+
+    if KAMAL.config.builder.git_clone?
+      if uncommitted_changes.present?
+        say "Building from a local git clone, so ignoring these uncommitted changes:\n #{uncommitted_changes}", :yellow
+      end
+
+      run_locally do
+        Clone.new(self).prepare
+      end
+    elsif uncommitted_changes.present?
+      say "Building with uncommitted changes:\n #{uncommitted_changes}", :yellow
+    end
+
+    with_env(KAMAL.config.builder.secrets) do
+      run_locally do
+        begin
+          execute *KAMAL.builder.inspect_builder
+        rescue SSHKit::Command::Failed => e
+          if e.message =~ /(context not found|no builder|no compatible builder|does not exist)/
+            warn "Missing compatible builder, so creating a new one first"
+            begin
+              cli.remove
+            rescue SSHKit::Command::Failed
+              raise unless e.message =~ /(context not found|no builder|does not exist)/
+            end
+            cli.create
+          else
+            raise
+          end
+        end
+
+        # Get the command here to ensure the Dir.chdir doesn't interfere with it
+        push = KAMAL.builder.push(cli.options[:output])
+
+        KAMAL.with_verbosity(:debug) do
+          Dir.chdir(KAMAL.config.builder.build_directory) { execute *push }
+        end
+      end
+    end
+  end
+
+  desc "pull", "Pull app image from registry onto servers"
+  def pull
+    login_to_registry_remotely
+
+    if (first_hosts = mirror_hosts).any?
+      #  Pull on a single host per mirror first to seed them
+      say "Pulling image on #{first_hosts.join(", ")} to seed the #{"mirror".pluralize(first_hosts.count)}...", :magenta
+      pull_on_hosts(first_hosts)
+      say "Pulling image on remaining hosts...", :magenta
+      pull_on_hosts(KAMAL.app_hosts - first_hosts)
+    else
+      pull_on_hosts(KAMAL.app_hosts)
+    end
+  end
+
+  desc "create", "Create a build setup"
+  def create
+    if (remote_host = KAMAL.config.builder.remote)
+      connect_to_remote_host(remote_host)
+    end
+
+    run_locally do
+      begin
+        debug "Using builder: #{KAMAL.builder.name}"
+        execute *KAMAL.builder.create
+      rescue SSHKit::Command::Failed => e
+        if e.message =~ /stderr=(.*)/
+          error "Couldn't create remote builder: #{$1}"
+          false
+        else
+          raise
+        end
+      end
+    end
+  end
+
+  desc "remove", "Remove build setup"
+  def remove
+    run_locally do
+      debug "Using builder: #{KAMAL.builder.name}"
+      execute *KAMAL.builder.remove
+    end
+  end
+
+  desc "details", "Show build setup"
+  def details
+    run_locally do
+      puts "Builder: #{KAMAL.builder.name}"
+      puts capture(*KAMAL.builder.info)
+    end
+  end
+
+  desc "dev", "Build using the working directory, tag it as dirty, and push to local image store."
+  option :output, type: :string, default: "docker", banner: "export_type", desc: "Exported type for the build result, and may be any exported type supported by 'buildx --output'."
+  def dev
+    cli = self
+
+    ensure_docker_installed
+
+    docker_included_files = Set.new(Kamal::Docker.included_files)
+    git_uncommitted_files = Set.new(Kamal::Git.uncommitted_files)
+    git_untracked_files = Set.new(Kamal::Git.untracked_files)
+
+    docker_uncommitted_files = docker_included_files & git_uncommitted_files
+    if docker_uncommitted_files.any?
+      say "WARNING: Files with uncommitted changes will be present in the dev container:", :yellow
+      docker_uncommitted_files.sort.each { |f| say "  #{f}", :yellow }
+      say
+    end
+
+    docker_untracked_files = docker_included_files & git_untracked_files
+    if docker_untracked_files.any?
+      say "WARNING: Untracked files will be present in the dev container:", :yellow
+      docker_untracked_files.sort.each { |f| say "  #{f}", :yellow }
+      say
+    end
+
+    with_env(KAMAL.config.builder.secrets) do
+      run_locally do
+        build = KAMAL.builder.push(cli.options[:output], tag_as_dirty: true)
+        KAMAL.with_verbosity(:debug) do
+          execute(*build)
+        end
+      end
+    end
+  end
+
+  private
+    def connect_to_remote_host(remote_host)
+      remote_uri = URI.parse(remote_host)
+      if remote_uri.scheme == "ssh"
+        host = SSHKit::Host.new(
+          hostname: remote_uri.host,
+          ssh_options: { user: remote_uri.user, port: remote_uri.port }.compact
+        )
+        on(host, options) do
+          execute "true"
+        end
+      end
+    end
+
+    def mirror_hosts
+      if KAMAL.app_hosts.many?
+        mirror_hosts = Concurrent::Hash.new
+        on(KAMAL.app_hosts) do |host|
+          first_mirror = capture_with_info(*KAMAL.builder.first_mirror).strip.presence
+          mirror_hosts[first_mirror] ||= host.to_s if first_mirror
+        rescue SSHKit::Command::Failed => e
+          raise unless e.message =~ /error calling index: reflect: slice index out of range/
+        end
+        mirror_hosts.values
+      else
+        []
+      end
+    end
+
+    def pull_on_hosts(hosts)
+      on(hosts) do
+        execute *KAMAL.auditor.record("Pulled image with version #{KAMAL.config.version}"), verbosity: :debug
+        execute *KAMAL.builder.clean, raise_on_non_zero_exit: false
+        execute *KAMAL.builder.pull
+        execute *KAMAL.builder.validate_image
+      end
+    end
+
+    def login_to_registry_locally
+      run_locally do
+        execute *KAMAL.registry.login
+      end
+    end
+
+    def login_to_registry_remotely
+      on(KAMAL.app_hosts) do
+        execute *KAMAL.registry.login
+      end
+    end
+end

lib/kamal/cli/build/clone.rb

@@ -0,0 +1,61 @@
+require "uri"
+
+class Kamal::Cli::Build::Clone
+  attr_reader :sshkit
+  delegate :info, :error, :execute, :capture_with_info, to: :sshkit
+
+  def initialize(sshkit)
+    @sshkit = sshkit
+  end
+
+  def prepare
+    begin
+      clone_repo
+    rescue SSHKit::Command::Failed => e
+      if e.message =~ /already exists and is not an empty directory/
+        reset
+      else
+        raise Kamal::Cli::Build::BuildError, "Failed to clone repo: #{e.message}"
+      end
+    end
+
+    validate!
+  rescue Kamal::Cli::Build::BuildError => e
+    error "Error preparing clone: #{e.message}, deleting and retrying..."
+
+    FileUtils.rm_rf KAMAL.config.builder.clone_directory
+    clone_repo
+    validate!
+  end
+
+  private
+    def clone_repo
+      info "Cloning repo into build directory `#{KAMAL.config.builder.build_directory}`..."
+
+      FileUtils.mkdir_p KAMAL.config.builder.clone_directory
+      execute *KAMAL.builder.clone
+    end
+
+    def reset
+      info "Resetting local clone as `#{KAMAL.config.builder.build_directory}` already exists..."
+
+      KAMAL.builder.clone_reset_steps.each { |step| execute *step }
+    rescue SSHKit::Command::Failed => e
+      raise Kamal::Cli::Build::BuildError, "Failed to clone repo: #{e.message}"
+    end
+
+    def validate!
+      status = capture_with_info(*KAMAL.builder.clone_status).strip
+
+      unless status.empty?
+        raise Kamal::Cli::Build::BuildError, "Clone in #{KAMAL.config.builder.build_directory} is dirty, #{status}"
+      end
+
+      revision = capture_with_info(*KAMAL.builder.clone_revision).strip
+      if revision != Kamal::Git.revision
+        raise Kamal::Cli::Build::BuildError, "Clone in #{KAMAL.config.builder.build_directory} is not on the correct revision, expected `#{Kamal::Git.revision}` but got `#{revision}`"
+      end
+    rescue SSHKit::Command::Failed => e
+      raise Kamal::Cli::Build::BuildError, "Failed to validate clone: #{e.message}"
+    end
+end

lib/kamal/cli/healthcheck/barrier.rb

@@ -0,0 +1,33 @@
+require "concurrent/ivar"
+
+class Kamal::Cli::Healthcheck::Barrier
+  def initialize
+    @ivar = Concurrent::IVar.new
+  end
+
+  def close
+    set(false)
+  end
+
+  def open
+    set(true)
+  end
+
+  def wait
+    unless opened?
+      raise Kamal::Cli::Healthcheck::Error.new("Halted at barrier")
+    end
+  end
+
+  private
+    def opened?
+      @ivar.value
+    end
+
+    def set(value)
+      @ivar.set(value)
+      true
+    rescue Concurrent::MultipleAssignmentError
+      false
+    end
+end

lib/kamal/cli/healthcheck/error.rb

@@ -0,0 +1,2 @@
+class Kamal::Cli::Healthcheck::Error < StandardError
+end

lib/kamal/cli/healthcheck/poller.rb

@@ -0,0 +1,42 @@
+module Kamal::Cli::Healthcheck::Poller
+  extend self
+
+  def wait_for_healthy(role, &block)
+    attempt = 1
+    timeout_at = Time.now + KAMAL.config.deploy_timeout
+    readiness_delay = KAMAL.config.readiness_delay
+
+    begin
+      status = block.call
+
+      if status == "running"
+        # Wait for the readiness delay and confirm it is still running
+        if readiness_delay > 0
+          info "Container is running, waiting for readiness delay of #{readiness_delay} seconds"
+          sleep readiness_delay
+          status = block.call
+        end
+      end
+
+      unless %w[ running healthy ].include?(status)
+        raise Kamal::Cli::Healthcheck::Error, "container not ready after #{KAMAL.config.deploy_timeout} seconds (#{status})"
+      end
+    rescue Kamal::Cli::Healthcheck::Error => e
+      time_left = timeout_at - Time.now
+      if time_left > 0
+        sleep [ attempt, time_left ].min
+        attempt += 1
+        retry
+      else
+        raise
+      end
+    end
+
+    info "Container is healthy!"
+  end
+
+  private
+    def info(message)
+      SSHKit.config.output.info(message)
+    end
+end

lib/kamal/cli/lock.rb

@@ -0,0 +1,45 @@
+class Kamal::Cli::Lock < Kamal::Cli::Base
+  desc "status", "Report lock status"
+  def status
+    handle_missing_lock do
+      on(KAMAL.primary_host) do
+        puts capture_with_debug(*KAMAL.lock.status)
+      end
+    end
+  end
+
+  desc "acquire", "Acquire the deploy lock"
+  option :message, aliases: "-m", type: :string, desc: "A lock message", required: true
+  def acquire
+    message = options[:message]
+    ensure_run_directory
+
+    raise_if_locked do
+      on(KAMAL.primary_host) do
+        execute *KAMAL.lock.acquire(message, KAMAL.config.version), verbosity: :debug
+      end
+      say "Acquired the deploy lock"
+    end
+  end
+
+  desc "release", "Release the deploy lock"
+  def release
+    handle_missing_lock do
+      on(KAMAL.primary_host) do
+        execute *KAMAL.lock.release, verbosity: :debug
+      end
+      say "Released the deploy lock"
+    end
+  end
+
+  private
+    def handle_missing_lock
+      yield
+    rescue SSHKit::Runner::ExecuteError => e
+      if e.message =~ /No such file or directory/
+        say "There is no deploy lock"
+      else
+        raise
+      end
+    end
+end

lib/kamal/cli/main.rb

@@ -0,0 +1,277 @@
+class Kamal::Cli::Main < Kamal::Cli::Base
+  desc "setup", "Setup all accessories, push the env, and deploy app to servers"
+  option :skip_push, aliases: "-P", type: :boolean, default: false, desc: "Skip image build and push"
+  def setup
+    print_runtime do
+      with_lock do
+        invoke_options = deploy_options
+
+        say "Ensure Docker is installed...", :magenta
+        invoke "kamal:cli:server:bootstrap", [], invoke_options
+
+        deploy(boot_accessories: true)
+      end
+    end
+  end
+
+  desc "deploy", "Deploy app to servers"
+  option :skip_push, aliases: "-P", type: :boolean, default: false, desc: "Skip image build and push"
+  def deploy(boot_accessories: false)
+    runtime = print_runtime do
+      invoke_options = deploy_options
+
+      if options[:skip_push]
+        say "Pull app image...", :magenta
+        invoke "kamal:cli:build:pull", [], invoke_options
+      else
+        say "Build and push app image...", :magenta
+        invoke "kamal:cli:build:deliver", [], invoke_options
+      end
+
+      with_lock do
+        run_hook "pre-deploy", secrets: true
+
+        say "Ensure kamal-proxy is running...", :magenta
+        invoke "kamal:cli:proxy:boot", [], invoke_options
+
+        invoke "kamal:cli:accessory:boot", [ "all" ], invoke_options if boot_accessories
+
+        say "Detect stale containers...", :magenta
+        invoke "kamal:cli:app:stale_containers", [], invoke_options.merge(stop: true)
+
+        invoke "kamal:cli:app:boot", [], invoke_options
+
+        say "Prune old containers and images...", :magenta
+        invoke "kamal:cli:prune:all", [], invoke_options
+      end
+    end
+
+    run_hook "post-deploy", secrets: true, runtime: runtime.round.to_s
+  end
+
+  desc "redeploy", "Deploy app to servers without bootstrapping servers, starting kamal-proxy and pruning"
+  option :skip_push, aliases: "-P", type: :boolean, default: false, desc: "Skip image build and push"
+  def redeploy
+    runtime = print_runtime do
+      invoke_options = deploy_options
+
+      if options[:skip_push]
+        say "Pull app image...", :magenta
+        invoke "kamal:cli:build:pull", [], invoke_options
+      else
+        say "Build and push app image...", :magenta
+        invoke "kamal:cli:build:deliver", [], invoke_options
+      end
+
+      with_lock do
+        run_hook "pre-deploy", secrets: true
+
+        say "Detect stale containers...", :magenta
+        invoke "kamal:cli:app:stale_containers", [], invoke_options.merge(stop: true)
+
+        invoke "kamal:cli:app:boot", [], invoke_options
+      end
+    end
+
+    run_hook "post-deploy", secrets: true, runtime: runtime.round.to_s
+  end
+
+  desc "rollback [VERSION]", "Rollback app to VERSION"
+  def rollback(version)
+    rolled_back = false
+    runtime = print_runtime do
+      with_lock do
+        invoke_options = deploy_options
+
+        KAMAL.config.version = version
+        old_version = nil
+
+        if container_available?(version)
+          run_hook "pre-deploy", secrets: true
+
+          invoke "kamal:cli:app:boot", [], invoke_options.merge(version: version)
+          rolled_back = true
+        else
+          say "The app version '#{version}' is not available as a container (use 'kamal app containers' for available versions)", :red
+        end
+      end
+    end
+
+    run_hook "post-deploy", secrets: true, runtime: runtime.round.to_s if rolled_back
+  end
+
+  desc "details", "Show details about all containers"
+  def details
+    invoke "kamal:cli:proxy:details"
+    invoke "kamal:cli:app:details"
+    invoke "kamal:cli:accessory:details", [ "all" ]
+  end
+
+  desc "audit", "Show audit log from servers"
+  def audit
+    on(KAMAL.hosts) do |host|
+      puts_by_host host, capture_with_info(*KAMAL.auditor.reveal)
+    end
+  end
+
+  desc "config", "Show combined config (including secrets!)"
+  def config
+    run_locally do
+      puts Kamal::Utils.redacted(KAMAL.config.to_h).to_yaml
+    end
+  end
+
+  desc "docs [SECTION]", "Show Kamal configuration documentation"
+  def docs(section = nil)
+    case section
+    when NilClass
+      puts Kamal::Configuration.validation_doc
+    else
+      puts Kamal::Configuration.const_get(section.titlecase.to_sym).validation_doc
+    end
+  rescue NameError
+    puts "No documentation found for #{section}"
+  end
+
+  desc "init", "Create config stub in config/deploy.yml and secrets stub in .kamal"
+  option :bundle, type: :boolean, default: false, desc: "Add Kamal to the Gemfile and create a bin/kamal binstub"
+  def init
+    require "fileutils"
+
+    if (deploy_file = Pathname.new(File.expand_path("config/deploy.yml"))).exist?
+      puts "Config file already exists in config/deploy.yml (remove first to create a new one)"
+    else
+      FileUtils.mkdir_p deploy_file.dirname
+      FileUtils.cp_r Pathname.new(File.expand_path("templates/deploy.yml", __dir__)), deploy_file
+      puts "Created configuration file in config/deploy.yml"
+    end
+
+    unless (secrets_file = Pathname.new(File.expand_path(".kamal/secrets"))).exist?
+      FileUtils.mkdir_p secrets_file.dirname
+      FileUtils.cp_r Pathname.new(File.expand_path("templates/secrets", __dir__)), secrets_file
+      puts "Created .kamal/secrets file"
+    end
+
+    unless (hooks_dir = Pathname.new(File.expand_path(".kamal/hooks"))).exist?
+      hooks_dir.mkpath
+      Pathname.new(File.expand_path("templates/sample_hooks", __dir__)).each_child do |sample_hook|
+        FileUtils.cp sample_hook, hooks_dir, preserve: true
+      end
+      puts "Created sample hooks in .kamal/hooks"
+    end
+
+    if options[:bundle]
+      if (binstub = Pathname.new(File.expand_path("bin/kamal"))).exist?
+        puts "Binstub already exists in bin/kamal (remove first to create a new one)"
+      else
+        puts "Adding Kamal to Gemfile and bundle..."
+        run_locally do
+          execute :bundle, :add, :kamal
+          execute :bundle, :binstubs, :kamal
+        end
+        puts "Created binstub file in bin/kamal"
+      end
+    end
+  end
+
+  desc "remove", "Remove kamal-proxy, app, accessories, and registry session from servers"
+  option :confirmed, aliases: "-y", type: :boolean, default: false, desc: "Proceed without confirmation question"
+  def remove
+    confirming "This will remove all containers and images. Are you sure?" do
+      with_lock do
+        invoke "kamal:cli:app:remove", [], options.without(:confirmed)
+        invoke "kamal:cli:proxy:remove", [], options.without(:confirmed)
+        invoke "kamal:cli:accessory:remove", [ "all" ], options
+        invoke "kamal:cli:registry:logout", [], options.without(:confirmed).merge(skip_local: true)
+      end
+    end
+  end
+
+  desc "upgrade", "Upgrade from Kamal 1.x to 2.0"
+  option :confirmed, aliases: "-y", type: :boolean, default: false, desc: "Proceed without confirmation question"
+  option :rolling, type: :boolean, default: false, desc: "Upgrade one host at a time"
+  def upgrade
+    confirming "This will replace Traefik with kamal-proxy and restart all accessories" do
+      with_lock do
+        if options[:rolling]
+          KAMAL.hosts.each do |host|
+            KAMAL.with_specific_hosts(host) do
+              say "Upgrading #{host}...", :magenta
+              if KAMAL.app_hosts.include?(host)
+                invoke "kamal:cli:proxy:upgrade", [], options.merge(confirmed: true, rolling: false)
+                reset_invocation(Kamal::Cli::Proxy)
+              end
+              if KAMAL.accessory_hosts.include?(host)
+                invoke "kamal:cli:accessory:upgrade", [ "all" ], options.merge(confirmed: true, rolling: false)
+                reset_invocation(Kamal::Cli::Accessory)
+              end
+              say "Upgraded #{host}", :magenta
+            end
+          end
+        else
+          say "Upgrading all hosts...", :magenta
+          invoke "kamal:cli:proxy:upgrade", [], options.merge(confirmed: true)
+          invoke "kamal:cli:accessory:upgrade", [ "all" ], options.merge(confirmed: true)
+          say "Upgraded all hosts", :magenta
+        end
+      end
+    end
+  end
+
+  desc "version", "Show Kamal version"
+  def version
+    puts Kamal::VERSION
+  end
+
+  desc "accessory", "Manage accessories (db/redis/search)"
+  subcommand "accessory", Kamal::Cli::Accessory
+
+  desc "app", "Manage application"
+  subcommand "app", Kamal::Cli::App
+
+  desc "build", "Build application image"
+  subcommand "build", Kamal::Cli::Build
+
+  desc "lock", "Manage the deploy lock"
+  subcommand "lock", Kamal::Cli::Lock
+
+  desc "proxy", "Manage kamal-proxy"
+  subcommand "proxy", Kamal::Cli::Proxy
+
+  desc "prune", "Prune old application images and containers"
+  subcommand "prune", Kamal::Cli::Prune
+
+  desc "registry", "Login and -out of the image registry"
+  subcommand "registry", Kamal::Cli::Registry
+
+  desc "secrets", "Helpers for extracting secrets"
+  subcommand "secrets", Kamal::Cli::Secrets
+
+  desc "server", "Bootstrap servers with curl and Docker"
+  subcommand "server", Kamal::Cli::Server
+
+  private
+    def container_available?(version)
+      begin
+        on(KAMAL.app_hosts) do
+          KAMAL.roles_on(host).each do |role|
+            container_id = capture_with_info(*KAMAL.app(role: role, host: host).container_id_for_version(version))
+            raise "Container not found" unless container_id.present?
+          end
+        end
+      rescue SSHKit::Runner::ExecuteError, SSHKit::Runner::MultipleExecuteError => e
+        if e.message =~ /Container not found/
+          say "Error looking for container version #{version}: #{e.message}"
+          return false
+        else
+          raise
+        end
+      end
+
+      true
+    end
+
+    def deploy_options
+      { "version" => KAMAL.config.version }.merge(options.without("skip_push"))
+    end
+end

lib/kamal/cli/proxy.rb

@@ -0,0 +1,290 @@
+class Kamal::Cli::Proxy < Kamal::Cli::Base
+  desc "boot", "Boot proxy on servers"
+  def boot
+    with_lock do
+      on(KAMAL.hosts) do |host|
+        execute *KAMAL.docker.create_network
+      rescue SSHKit::Command::Failed => e
+        raise unless e.message.include?("already exists")
+      end
+
+      on(KAMAL.proxy_hosts) do |host|
+        execute *KAMAL.registry.login
+
+        version = capture_with_info(*KAMAL.proxy.version).strip.presence
+
+        if version && Kamal::Utils.older_version?(version, Kamal::Configuration::Proxy::Boot::MINIMUM_VERSION)
+          raise "kamal-proxy version #{version} is too old, run `kamal proxy reboot` in order to update to at least #{Kamal::Configuration::Proxy::Boot::MINIMUM_VERSION}"
+        end
+        execute *KAMAL.proxy.ensure_apps_config_directory
+        execute *KAMAL.proxy.start_or_run
+      end
+    end
+  end
+
+  desc "boot_config <set|get|reset>", "Manage kamal-proxy boot configuration"
+  option :publish, type: :boolean, default: true, desc: "Publish the proxy ports on the host"
+  option :publish_host_ip, type: :string, repeatable: true, default: nil, desc: "Host IP address to bind HTTP/HTTPS traffic to. Defaults to all interfaces"
+  option :http_port, type: :numeric, default: Kamal::Configuration::Proxy::Boot::DEFAULT_HTTP_PORT, desc: "HTTP port to publish on the host"
+  option :https_port, type: :numeric, default: Kamal::Configuration::Proxy::Boot::DEFAULT_HTTPS_PORT, desc: "HTTPS port to publish on the host"
+  option :log_max_size, type: :string, default: Kamal::Configuration::Proxy::Boot::DEFAULT_LOG_MAX_SIZE, desc: "Max size of proxy logs"
+  option :registry, type: :string, default: nil, desc: "Registry to use for the proxy image"
+  option :repository, type: :string, default: nil, desc: "Repository for the proxy image"
+  option :image_version, type: :string, default: nil, desc: "Version of the proxy to run"
+  option :metrics_port, type: :numeric, default: nil, desc: "Port to report prometheus metrics on"
+  option :debug, type: :boolean, default: false, desc: "Whether to run the proxy in debug mode"
+  option :docker_options, type: :array, default: [], desc: "Docker options to pass to the proxy container", banner: "option=value option2=value2"
+  def boot_config(subcommand)
+    proxy_boot_config = KAMAL.config.proxy_boot
+
+    case subcommand
+    when "set"
+      boot_options = [
+        *(proxy_boot_config.publish_args(options[:http_port], options[:https_port], options[:publish_host_ip]) if options[:publish]),
+        *(proxy_boot_config.logging_args(options[:log_max_size])),
+        *("--expose=#{options[:metrics_port]}" if options[:metrics_port]),
+        *options[:docker_options].map { |option| "--#{option}" }
+      ]
+
+      image = [
+        options[:registry].presence,
+        options[:repository].presence || proxy_boot_config.repository_name,
+        proxy_boot_config.image_name
+      ].compact.join("/")
+
+      image_version = options[:image_version]
+
+      run_command_options = { debug: options[:debug] || nil, "metrics-port": options[:metrics_port] }.compact
+      run_command = "kamal-proxy run #{Kamal::Utils.optionize(run_command_options).join(" ")}" if run_command_options.any?
+
+      on(KAMAL.proxy_hosts) do |host|
+        execute(*KAMAL.proxy.ensure_proxy_directory)
+        if boot_options != proxy_boot_config.default_boot_options
+          upload! StringIO.new(boot_options.join(" ")), proxy_boot_config.options_file
+        else
+          execute *KAMAL.proxy.reset_boot_options, raise_on_non_zero_exit: false
+        end
+
+        if image != proxy_boot_config.image_default
+          upload! StringIO.new(image), proxy_boot_config.image_file
+        else
+          execute *KAMAL.proxy.reset_image, raise_on_non_zero_exit: false
+        end
+
+        if image_version
+          upload! StringIO.new(image_version), proxy_boot_config.image_version_file
+        else
+          execute *KAMAL.proxy.reset_image_version, raise_on_non_zero_exit: false
+        end
+
+        if run_command
+          upload! StringIO.new(run_command), proxy_boot_config.run_command_file
+        else
+          execute *KAMAL.proxy.reset_run_command, raise_on_non_zero_exit: false
+        end
+      end
+    when "get"
+
+      on(KAMAL.proxy_hosts) do |host|
+        puts "Host #{host}: #{capture_with_info(*KAMAL.proxy.boot_config)}"
+      end
+    when "reset"
+      on(KAMAL.proxy_hosts) do |host|
+        execute *KAMAL.proxy.reset_boot_options, raise_on_non_zero_exit: false
+        execute *KAMAL.proxy.reset_image, raise_on_non_zero_exit: false
+        execute *KAMAL.proxy.reset_image_version, raise_on_non_zero_exit: false
+        execute *KAMAL.proxy.reset_run_command, raise_on_non_zero_exit: false
+      end
+    else
+      raise ArgumentError, "Unknown boot_config subcommand #{subcommand}"
+    end
+  end
+
+  desc "reboot", "Reboot proxy on servers (stop container, remove container, start new container)"
+  option :rolling, type: :boolean, default: false, desc: "Reboot proxy on hosts in sequence, rather than in parallel"
+  option :confirmed, aliases: "-y", type: :boolean, default: false, desc: "Proceed without confirmation question"
+  def reboot
+    confirming "This will cause a brief outage on each host. Are you sure?" do
+      with_lock do
+        host_groups = options[:rolling] ? KAMAL.proxy_hosts : [ KAMAL.proxy_hosts ]
+        host_groups.each do |hosts|
+          host_list = Array(hosts).join(",")
+          run_hook "pre-proxy-reboot", hosts: host_list
+          on(hosts) do |host|
+            execute *KAMAL.auditor.record("Rebooted proxy"), verbosity: :debug
+            execute *KAMAL.registry.login
+
+            "Stopping and removing kamal-proxy on #{host}, if running..."
+            execute *KAMAL.proxy.stop, raise_on_non_zero_exit: false
+            execute *KAMAL.proxy.remove_container
+            execute *KAMAL.proxy.ensure_apps_config_directory
+
+            execute *KAMAL.proxy.run
+          end
+          run_hook "post-proxy-reboot", hosts: host_list
+        end
+      end
+    end
+  end
+
+  desc "upgrade", "Upgrade to kamal-proxy on servers (stop container, remove container, start new container, reboot app)", hide: true
+  option :rolling, type: :boolean, default: false, desc: "Reboot proxy on hosts in sequence, rather than in parallel"
+  option :confirmed, aliases: "-y", type: :boolean, default: false, desc: "Proceed without confirmation question"
+  def upgrade
+    invoke_options = { "version" => KAMAL.config.latest_tag }.merge(options)
+
+    confirming "This will cause a brief outage on each host. Are you sure?" do
+      host_groups = options[:rolling] ? KAMAL.hosts : [ KAMAL.hosts ]
+      host_groups.each do |hosts|
+        host_list = Array(hosts).join(",")
+        say "Upgrading proxy on #{host_list}...", :magenta
+        run_hook "pre-proxy-reboot", hosts: host_list
+        on(hosts) do |host|
+          execute *KAMAL.auditor.record("Rebooted proxy"), verbosity: :debug
+          execute *KAMAL.registry.login
+
+          "Stopping and removing Traefik on #{host}, if running..."
+          execute *KAMAL.proxy.cleanup_traefik
+
+          "Stopping and removing kamal-proxy on #{host}, if running..."
+          execute *KAMAL.proxy.stop, raise_on_non_zero_exit: false
+          execute *KAMAL.proxy.remove_container
+          execute *KAMAL.proxy.remove_image
+        end
+
+        KAMAL.with_specific_hosts(hosts) do
+          invoke "kamal:cli:proxy:boot", [], invoke_options
+          reset_invocation(Kamal::Cli::Proxy)
+          invoke "kamal:cli:app:boot", [], invoke_options
+          reset_invocation(Kamal::Cli::App)
+          invoke "kamal:cli:prune:all", [], invoke_options
+          reset_invocation(Kamal::Cli::Prune)
+        end
+
+        run_hook "post-proxy-reboot", hosts: host_list
+        say "Upgraded proxy on #{host_list}", :magenta
+      end
+    end
+  end
+
+  desc "start", "Start existing proxy container on servers"
+  def start
+    with_lock do
+      on(KAMAL.proxy_hosts) do |host|
+        execute *KAMAL.auditor.record("Started proxy"), verbosity: :debug
+        execute *KAMAL.proxy.start
+      end
+    end
+  end
+
+  desc "stop", "Stop existing proxy container on servers"
+  def stop
+    with_lock do
+      on(KAMAL.proxy_hosts) do |host|
+        execute *KAMAL.auditor.record("Stopped proxy"), verbosity: :debug
+        execute *KAMAL.proxy.stop, raise_on_non_zero_exit: false
+      end
+    end
+  end
+
+  desc "restart", "Restart existing proxy container on servers"
+  def restart
+    with_lock do
+      stop
+      start
+    end
+  end
+
+  desc "details", "Show details about proxy container from servers"
+  def details
+    on(KAMAL.proxy_hosts) { |host| puts_by_host host, capture_with_info(*KAMAL.proxy.info), type: "Proxy" }
+  end
+
+  desc "logs", "Show log lines from proxy on servers"
+  option :since, aliases: "-s", desc: "Show logs since timestamp (e.g. 2013-01-02T13:23:37Z) or relative (e.g. 42m for 42 minutes)"
+  option :lines, type: :numeric, aliases: "-n", desc: "Number of log lines to pull from each server"
+  option :grep, aliases: "-g", desc: "Show lines with grep match only (use this to fetch specific requests by id)"
+  option :follow, aliases: "-f", desc: "Follow logs on primary server (or specific host set by --hosts)"
+  option :skip_timestamps, type: :boolean, aliases: "-T", desc: "Skip appending timestamps to logging output"
+  def logs
+    grep = options[:grep]
+    timestamps = !options[:skip_timestamps]
+
+    if options[:follow]
+      run_locally do
+        info "Following logs on #{KAMAL.primary_host}..."
+        info KAMAL.proxy.follow_logs(host: KAMAL.primary_host, timestamps: timestamps, grep: grep)
+        exec KAMAL.proxy.follow_logs(host: KAMAL.primary_host, timestamps: timestamps, grep: grep)
+      end
+    else
+      since = options[:since]
+      lines = options[:lines].presence || ((since || grep) ? nil : 100) # Default to 100 lines if since or grep isn't set
+
+      on(KAMAL.proxy_hosts) do |host|
+        puts_by_host host, capture(*KAMAL.proxy.logs(timestamps: timestamps, since: since, lines: lines, grep: grep)), type: "Proxy"
+      end
+    end
+  end
+
+  desc "remove", "Remove proxy container and image from servers"
+  option :force, type: :boolean, default: false, desc: "Force removing proxy when apps are still installed"
+  def remove
+    with_lock do
+      if removal_allowed?(options[:force])
+        stop
+        remove_container
+        remove_image
+        remove_proxy_directory
+      end
+    end
+  end
+
+  desc "remove_container", "Remove proxy container from servers", hide: true
+  def remove_container
+    with_lock do
+      on(KAMAL.proxy_hosts) do
+        execute *KAMAL.auditor.record("Removed proxy container"), verbosity: :debug
+        execute *KAMAL.proxy.remove_container
+      end
+    end
+  end
+
+  desc "remove_image", "Remove proxy image from servers", hide: true
+  def remove_image
+    with_lock do
+      on(KAMAL.proxy_hosts) do
+        execute *KAMAL.auditor.record("Removed proxy image"), verbosity: :debug
+        execute *KAMAL.proxy.remove_image
+      end
+    end
+  end
+
+  desc "remove_proxy_directory", "Remove the proxy directory from servers", hide: true
+  def remove_proxy_directory
+    with_lock do
+      on(KAMAL.proxy_hosts) do
+        execute *KAMAL.proxy.remove_proxy_directory, raise_on_non_zero_exit: false
+      end
+    end
+  end
+
+  private
+    def removal_allowed?(force)
+      on(KAMAL.proxy_hosts) do |host|
+        app_count = capture_with_info(*KAMAL.server.app_directory_count).chomp.to_i
+        raise "The are other applications installed on #{host}" if app_count > 0
+      end
+
+      true
+    rescue SSHKit::Runner::ExecuteError => e
+      raise unless e.message.include?("The are other applications installed on")
+
+      if force
+        say "Forcing, so removing the proxy, even though other apps are installed", :magenta
+      else
+        say "Not removing the proxy, as other apps are installed, ignore this check with kamal proxy remove --force", :magenta
+      end
+
+      force
+    end
+end

lib/kamal/cli/prune.rb

@@ -0,0 +1,34 @@
+class Kamal::Cli::Prune < Kamal::Cli::Base
+  desc "all", "Prune unused images and stopped containers"
+  def all
+    with_lock do
+      containers
+      images
+    end
+  end
+
+  desc "images", "Prune unused images"
+  def images
+    with_lock do
+      on(KAMAL.hosts) do
+        execute *KAMAL.auditor.record("Pruned images"), verbosity: :debug
+        execute *KAMAL.prune.dangling_images
+        execute *KAMAL.prune.tagged_images
+      end
+    end
+  end
+
+  desc "containers", "Prune all stopped containers, except the last n (default 5)"
+  option :retain, type: :numeric, default: nil, desc: "Number of containers to retain"
+  def containers
+    retain = options.fetch(:retain, KAMAL.config.retain_containers)
+    raise "retain must be at least 1" if retain < 1
+
+    with_lock do
+      on(KAMAL.hosts) do
+        execute *KAMAL.auditor.record("Pruned containers"), verbosity: :debug
+        execute *KAMAL.prune.app_containers(retain: retain)
+      end
+    end
+  end
+end

lib/kamal/cli/registry.rb

@@ -0,0 +1,19 @@
+class Kamal::Cli::Registry < Kamal::Cli::Base
+  desc "login", "Log in to registry locally and remotely"
+  option :skip_local, aliases: "-L", type: :boolean, default: false, desc: "Skip local login"
+  option :skip_remote, aliases: "-R", type: :boolean, default: false, desc: "Skip remote login"
+  def login
+    ensure_docker_installed unless options[:skip_local]
+
+    run_locally    { execute *KAMAL.registry.login } unless options[:skip_local]
+    on(KAMAL.hosts) { execute *KAMAL.registry.login } unless options[:skip_remote]
+  end
+
+  desc "logout", "Log out of registry locally and remotely"
+  option :skip_local, aliases: "-L", type: :boolean, default: false, desc: "Skip local login"
+  option :skip_remote, aliases: "-R", type: :boolean, default: false, desc: "Skip remote login"
+  def logout
+    run_locally    { execute *KAMAL.registry.logout } unless options[:skip_local]
+    on(KAMAL.hosts) { execute *KAMAL.registry.logout } unless options[:skip_remote]
+  end
+end

lib/kamal/cli/secrets.rb

@@ -0,0 +1,49 @@
+class Kamal::Cli::Secrets < Kamal::Cli::Base
+  desc "fetch [SECRETS...]", "Fetch secrets from a vault"
+  option :adapter, type: :string, aliases: "-a", required: true, desc: "Which vault adapter to use"
+  option :account, type: :string, required: false, desc: "The account identifier or username"
+  option :from, type: :string, required: false, desc: "A vault or folder to fetch the secrets from"
+  option :inline, type: :boolean, required: false, hidden: true
+  def fetch(*secrets)
+    adapter = initialize_adapter(options[:adapter])
+
+    if adapter.requires_account? && options[:account].blank?
+      return puts "No value provided for required options '--account'"
+    end
+
+    results = adapter.fetch(secrets, **options.slice(:account, :from).symbolize_keys)
+
+    return_or_puts JSON.dump(results).shellescape, inline: options[:inline]
+  end
+
+  desc "extract", "Extract a single secret from the results of a fetch call"
+  option :inline, type: :boolean, required: false, hidden: true
+  def extract(name, secrets)
+    parsed_secrets = JSON.parse(secrets)
+    value = parsed_secrets[name] || parsed_secrets.find { |k, v| k.end_with?("/#{name}") }&.last
+
+    raise "Could not find secret #{name}" if value.nil?
+
+    return_or_puts value, inline: options[:inline]
+  end
+
+  desc "print", "Print the secrets (for debugging)"
+  def print
+    KAMAL.config.secrets.to_h.each do |key, value|
+      puts "#{key}=#{value}"
+    end
+  end
+
+  private
+    def initialize_adapter(adapter)
+      Kamal::Secrets::Adapters.lookup(adapter)
+    end
+
+    def return_or_puts(value, inline: nil)
+      if inline
+        value
+      else
+        puts value
+      end
+    end
+end

lib/kamal/cli/server.rb

@@ -0,0 +1,50 @@
+class Kamal::Cli::Server < Kamal::Cli::Base
+  desc "exec", "Run a custom command on the server (use --help to show options)"
+  option :interactive, type: :boolean, aliases: "-i", default: false, desc: "Run the command interactively (use for console/bash)"
+  def exec(*cmd)
+    pre_connect_if_required
+
+    cmd = Kamal::Utils.join_commands(cmd)
+    hosts = KAMAL.hosts
+
+    case
+    when options[:interactive]
+      host = KAMAL.primary_host
+
+      say "Running '#{cmd}' on #{host} interactively...", :magenta
+
+      run_locally { exec KAMAL.server.run_over_ssh(cmd, host: host) }
+    else
+      say "Running '#{cmd}' on #{hosts.join(', ')}...", :magenta
+
+      on(hosts) do |host|
+        execute *KAMAL.auditor.record("Executed cmd '#{cmd}' on #{host}"), verbosity: :debug
+        puts_by_host host, capture_with_info(cmd)
+      end
+    end
+  end
+
+  desc "bootstrap", "Set up Docker to run Kamal apps"
+  def bootstrap
+    with_lock do
+      missing = []
+
+      on(KAMAL.hosts) do |host|
+        unless execute(*KAMAL.docker.installed?, raise_on_non_zero_exit: false)
+          if execute(*KAMAL.docker.superuser?, raise_on_non_zero_exit: false)
+            info "Missing Docker on #{host}. Installing…"
+            execute *KAMAL.docker.install
+          else
+            missing << host
+          end
+        end
+      end
+
+      if missing.any?
+        raise "Docker is not installed on #{missing.join(", ")} and can't be automatically installed without having root access and either `wget` or `curl`. Install Docker manually: https://docs.docker.com/engine/install/"
+      end
+
+      run_hook "docker-setup"
+    end
+  end
+end

lib/kamal/cli/templates/deploy.yml

@@ -0,0 +1,101 @@
+# Name of your application. Used to uniquely configure containers.
+service: my-app
+
+# Name of the container image.
+image: my-user/my-app
+
+# Deploy to these servers.
+servers:
+  web:
+    - 192.168.0.1
+  # 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
+  # Proxy connects to your container on port 80 by default.
+  # app_port: 3000
+
+# Credentials for your image host.
+registry:
+  # Specify the registry server, if you're not using Docker Hub
+  # server: registry.digitalocean.com / ghcr.io / ...
+  username: my-user
+
+  # Always use an access token rather than real password (pulled from .kamal/secrets).
+  password:
+    - KAMAL_REGISTRY_PASSWORD
+
+# Configure builder setup.
+builder:
+  arch: amd64
+  # Pass in additional build args needed for your Dockerfile.
+  # args:
+  #   RUBY_VERSION: <%= ENV["RBENV_VERSION"] || ENV["rvm_ruby_string"] || "#{RUBY_ENGINE}-#{RUBY_ENGINE_VERSION}" %>
+
+# Inject ENV variables into containers (secrets come from .kamal/secrets).
+#
+# env:
+#   clear:
+#     DB_HOST: 192.168.0.2
+#   secret:
+#     - RAILS_MASTER_KEY
+
+# Aliases are triggered with "bin/kamal <alias>". You can overwrite arguments on invocation:
+# "bin/kamal app logs -r job" will tail logs from the first server in the job section.
+#
+# aliases:
+#   shell: app exec --interactive --reuse "bash"
+
+# Use a different ssh user than root
+#
+# ssh:
+#   user: app
+
+# Use a persistent storage volume.
+#
+# volumes:
+#   - "app_storage:/app/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: /app/public/assets
+
+# Configure rolling deploys by setting a wait time between batches of restarts.
+#
+# boot:
+#   limit: 10 # Can also specify as a percentage of total hosts, such as "25%"
+#   wait: 2
+
+# Use accessory services (secrets come from .kamal/secrets).
+#
+# accessories:
+#   db:
+#     image: mysql:8.0
+#     host: 192.168.0.2
+#     port: 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: valkey/valkey:8
+#     host: 192.168.0.2
+#     port: 6379
+#     directories:
+#       - data:/data

lib/kamal/cli/templates/sample_hooks/docker-setup.sample

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+echo "Docker set up on $KAMAL_HOSTS..."

lib/kamal/cli/templates/sample_hooks/post-app-boot.sample

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+echo "Booted app version $KAMAL_VERSION on $KAMAL_HOSTS..."

lib/kamal/cli/templates/sample_hooks/post-deploy.sample

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+# A sample post-deploy hook
+#
+# These environment variables are available:
+# KAMAL_RECORDED_AT
+# KAMAL_PERFORMER
+# KAMAL_VERSION
+# KAMAL_HOSTS
+# KAMAL_ROLES (if set)
+# KAMAL_DESTINATION (if set)
+# KAMAL_RUNTIME
+
+echo "$KAMAL_PERFORMER deployed $KAMAL_VERSION to $KAMAL_DESTINATION in $KAMAL_RUNTIME seconds"

lib/kamal/cli/templates/sample_hooks/post-proxy-reboot.sample

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+echo "Rebooted kamal-proxy on $KAMAL_HOSTS"

lib/kamal/cli/templates/sample_hooks/pre-app-boot.sample

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+echo "Booting app version $KAMAL_VERSION on $KAMAL_HOSTS..."

lib/kamal/cli/templates/sample_hooks/pre-build.sample

@@ -0,0 +1,51 @@
+#!/bin/sh
+
+# A sample pre-build hook
+#
+# Checks:
+# 1. We have a clean checkout
+# 2. A remote is configured
+# 3. The branch has been pushed to the remote
+# 4. The version we are deploying matches the remote
+#
+# These environment variables are available:
+# KAMAL_RECORDED_AT
+# KAMAL_PERFORMER
+# KAMAL_VERSION
+# KAMAL_HOSTS
+# KAMAL_ROLES (if set)
+# KAMAL_DESTINATION (if set)
+
+if [ -n "$(git status --porcelain)" ]; then
+  echo "Git checkout is not clean, aborting..." >&2
+  git status --porcelain >&2
+  exit 1
+fi
+
+first_remote=$(git remote)
+
+if [ -z "$first_remote" ]; then
+  echo "No git remote set, aborting..." >&2
+  exit 1
+fi
+
+current_branch=$(git branch --show-current)
+
+if [ -z "$current_branch" ]; then
+  echo "Not on a git branch, aborting..." >&2
+  exit 1
+fi
+
+remote_head=$(git ls-remote $first_remote --tags $current_branch | cut -f1)
+
+if [ -z "$remote_head" ]; then
+  echo "Branch not pushed to remote, aborting..." >&2
+  exit 1
+fi
+
+if [ "$KAMAL_VERSION" != "$remote_head" ]; then
+  echo "Version ($KAMAL_VERSION) does not match remote HEAD ($remote_head), aborting..." >&2
+  exit 1
+fi
+
+exit 0

lib/kamal/cli/templates/sample_hooks/pre-connect.sample

@@ -0,0 +1,47 @@
+#!/usr/bin/env ruby
+
+# A sample pre-connect check
+#
+# Warms DNS before connecting to hosts in parallel
+#
+# These environment variables are available:
+# KAMAL_RECORDED_AT
+# KAMAL_PERFORMER
+# KAMAL_VERSION
+# KAMAL_HOSTS
+# KAMAL_ROLES (if set)
+# KAMAL_DESTINATION (if set)
+# KAMAL_RUNTIME
+
+hosts = ENV["KAMAL_HOSTS"].split(",")
+results = nil
+max = 3
+
+elapsed = Benchmark.realtime do
+  results = hosts.map do |host|
+    Thread.new do
+      tries = 1
+
+      begin
+        Socket.getaddrinfo(host, 0, Socket::AF_UNSPEC, Socket::SOCK_STREAM, nil, Socket::AI_CANONNAME)
+      rescue SocketError
+        if tries < max
+          puts "Retrying DNS warmup: #{host}"
+          tries += 1
+          sleep rand
+          retry
+        else
+          puts "DNS warmup failed: #{host}"
+          host
+        end
+      end
+
+      tries
+    end
+  end.map(&:value)
+end
+
+retries = results.sum - hosts.size
+nopes = results.count { |r| r == max }
+
+puts "Prewarmed %d DNS lookups in %.2f sec: %d retries, %d failures" % [ hosts.size, elapsed, retries, nopes ]

lib/kamal/cli/templates/sample_hooks/pre-deploy.sample

@@ -0,0 +1,122 @@
+#!/usr/bin/env ruby
+
+# A sample pre-deploy hook
+#
+# Checks the Github status of the build, waiting for a pending build to complete for up to 720 seconds.
+#
+# Fails unless the combined status is "success"
+#
+# These environment variables are available:
+# KAMAL_RECORDED_AT
+# KAMAL_PERFORMER
+# KAMAL_VERSION
+# KAMAL_HOSTS
+# KAMAL_COMMAND
+# KAMAL_SUBCOMMAND
+# KAMAL_ROLES (if set)
+# KAMAL_DESTINATION (if set)
+
+# Only check the build status for production deployments
+if ENV["KAMAL_COMMAND"] == "rollback" || ENV["KAMAL_DESTINATION"] != "production"
+  exit 0
+end
+
+require "bundler/inline"
+
+# true = install gems so this is fast on repeat invocations
+gemfile(true, quiet: true) do
+  source "https://rubygems.org"
+
+  gem "octokit"
+  gem "faraday-retry"
+end
+
+MAX_ATTEMPTS = 72
+ATTEMPTS_GAP = 10
+
+def exit_with_error(message)
+  $stderr.puts message
+  exit 1
+end
+
+class GithubStatusChecks
+  attr_reader :remote_url, :git_sha, :github_client, :combined_status
+
+  def initialize
+    @remote_url = github_repo_from_remote_url
+    @git_sha = `git rev-parse HEAD`.strip
+    @github_client = Octokit::Client.new(access_token: ENV["GITHUB_TOKEN"])
+    refresh!
+  end
+
+  def refresh!
+    @combined_status = github_client.combined_status(remote_url, git_sha)
+  end
+
+  def state
+    combined_status[:state]
+  end
+
+  def first_status_url
+    first_status = combined_status[:statuses].find { |status| status[:state] == state }
+    first_status && first_status[:target_url]
+  end
+
+  def complete_count
+    combined_status[:statuses].count { |status| status[:state] != "pending"}
+  end
+
+  def total_count
+    combined_status[:statuses].count
+  end
+
+  def current_status
+    if total_count > 0
+      "Completed #{complete_count}/#{total_count} checks, see #{first_status_url} ..."
+    else
+      "Build not started..."
+    end
+  end
+
+  private
+    def github_repo_from_remote_url
+      url = `git config --get remote.origin.url`.strip.delete_suffix(".git")
+      if url.start_with?("https://github.com/")
+        url.delete_prefix("https://github.com/")
+      elsif url.start_with?("git@github.com:")
+        url.delete_prefix("git@github.com:")
+      else
+        url
+      end
+    end
+end
+
+
+$stdout.sync = true
+
+begin
+  puts "Checking build status..."
+
+  attempts = 0
+  checks = GithubStatusChecks.new
+
+  loop do
+    case checks.state
+    when "success"
+      puts "Checks passed, see #{checks.first_status_url}"
+      exit 0
+    when "failure"
+      exit_with_error "Checks failed, see #{checks.first_status_url}"
+    when "pending"
+      attempts += 1
+    end
+
+    exit_with_error "Checks are still pending, gave up after #{MAX_ATTEMPTS * ATTEMPTS_GAP} seconds" if attempts == MAX_ATTEMPTS
+
+    puts checks.current_status
+    sleep(ATTEMPTS_GAP)
+    checks.refresh!
+  end
+rescue Octokit::NotFound
+  exit_with_error "Build status could not be found"
+end

lib/kamal/cli/templates/sample_hooks/pre-proxy-reboot.sample

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+echo "Rebooting kamal-proxy on $KAMAL_HOSTS..."

lib/kamal/cli/templates/secrets

@@ -0,0 +1,17 @@
+# Secrets defined here are available for reference under registry/password, env/secret, builder/secrets,
+# and accessories/*/env/secret in config/deploy.yml. All secrets should be pulled from either
+# password manager, ENV, or a file. DO NOT ENTER RAW CREDENTIALS HERE! This file needs to be safe for git.
+
+# Option 1: Read secrets from the environment
+KAMAL_REGISTRY_PASSWORD=$KAMAL_REGISTRY_PASSWORD
+
+# Option 2: Read secrets via a command
+# RAILS_MASTER_KEY=$(cat config/master.key)
+
+# Option 3: Read secrets via kamal secrets helpers
+# These will handle logging in and fetching the secrets in as few calls as possible
+# There are adapters for 1Password, LastPass + Bitwarden
+#
+# SECRETS=$(kamal secrets fetch --adapter 1password --account my-account --from MyVault/MyItem KAMAL_REGISTRY_PASSWORD RAILS_MASTER_KEY)
+# KAMAL_REGISTRY_PASSWORD=$(kamal secrets extract KAMAL_REGISTRY_PASSWORD $SECRETS)
+# RAILS_MASTER_KEY=$(kamal secrets extract RAILS_MASTER_KEY $SECRETS)

lib/kamal/commander.rb

@@ -0,0 +1,167 @@
+require "active_support/core_ext/enumerable"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/object/blank"
+
+class Kamal::Commander
+  attr_accessor :verbosity, :holding_lock, :connected
+  attr_reader :specific_roles, :specific_hosts
+  delegate :hosts, :roles, :primary_host, :primary_role, :roles_on, :app_hosts, :proxy_hosts, :accessory_hosts, to: :specifics
+
+  def initialize
+    reset
+  end
+
+  def reset
+    self.verbosity = :info
+    self.holding_lock = ENV["KAMAL_LOCK"] == "true"
+    self.connected = false
+    @specifics = @specific_roles = @specific_hosts = nil
+    @config = @config_kwargs = nil
+    @commands = {}
+  end
+
+  def config
+    @config ||= Kamal::Configuration.create_from(**@config_kwargs).tap do |config|
+      @config_kwargs = nil
+      configure_sshkit_with(config)
+    end
+  end
+
+  def configure(**kwargs)
+    @config, @config_kwargs = nil, kwargs
+  end
+
+  def configured?
+    @config || @config_kwargs
+  end
+
+  def specific_primary!
+    @specifics = nil
+    if specific_roles.present?
+      self.specific_hosts = [ specific_roles.first.primary_host ]
+    else
+      self.specific_hosts = [ config.primary_host ]
+    end
+  end
+
+  def specific_roles=(role_names)
+    @specifics = nil
+    if role_names.present?
+      @specific_roles = Kamal::Utils.filter_specific_items(role_names, config.roles)
+
+      if @specific_roles.empty?
+        raise ArgumentError, "No --roles match for #{role_names.join(',')}"
+      end
+
+      @specific_roles
+    end
+  end
+
+  def specific_hosts=(hosts)
+    @specifics = nil
+    if hosts.present?
+      @specific_hosts = Kamal::Utils.filter_specific_items(hosts, config.all_hosts)
+
+      if @specific_hosts.empty?
+        raise ArgumentError, "No --hosts match for #{hosts.join(',')}"
+      end
+
+      @specific_hosts
+    end
+  end
+
+  def with_specific_hosts(hosts)
+    original_hosts, self.specific_hosts = specific_hosts, hosts
+    yield
+  ensure
+    self.specific_hosts = original_hosts
+  end
+
+  def accessory_names
+    config.accessories&.collect(&:name) || []
+  end
+
+  def app(role: nil, host: nil)
+    Kamal::Commands::App.new(config, role: role, host: host)
+  end
+
+  def accessory(name)
+    Kamal::Commands::Accessory.new(config, name: name)
+  end
+
+  def auditor(**details)
+    Kamal::Commands::Auditor.new(config, **details)
+  end
+
+  def builder
+    @commands[:builder] ||= Kamal::Commands::Builder.new(config)
+  end
+
+  def docker
+    @commands[:docker] ||= Kamal::Commands::Docker.new(config)
+  end
+
+  def hook
+    @commands[:hook] ||= Kamal::Commands::Hook.new(config)
+  end
+
+  def lock
+    @commands[:lock] ||= Kamal::Commands::Lock.new(config)
+  end
+
+  def proxy
+    @commands[:proxy] ||= Kamal::Commands::Proxy.new(config)
+  end
+
+  def prune
+    @commands[:prune] ||= Kamal::Commands::Prune.new(config)
+  end
+
+  def registry
+    @commands[:registry] ||= Kamal::Commands::Registry.new(config)
+  end
+
+  def server
+    @commands[:server] ||= Kamal::Commands::Server.new(config)
+  end
+
+  def alias(name)
+    config.aliases[name]
+  end
+
+  def with_verbosity(level)
+    old_level = self.verbosity
+
+    self.verbosity = level
+    SSHKit.config.output_verbosity = level
+
+    yield
+  ensure
+    self.verbosity = old_level
+    SSHKit.config.output_verbosity = old_level
+  end
+
+  def holding_lock?
+    self.holding_lock
+  end
+
+  def connected?
+    self.connected
+  end
+
+  private
+    # Lazy setup of SSHKit
+    def configure_sshkit_with(config)
+      SSHKit::Backend::Netssh.pool.idle_timeout = config.sshkit.pool_idle_timeout
+      SSHKit::Backend::Netssh.configure do |sshkit|
+        sshkit.max_concurrent_starts = config.sshkit.max_concurrent_starts
+        sshkit.ssh_options = config.ssh.options
+      end
+      SSHKit.config.command_map[:docker] = "docker" # No need to use /usr/bin/env, just clogs up the logs
+      SSHKit.config.output_verbosity = verbosity
+    end
+
+    def specifics
+      @specifics ||= Kamal::Commander::Specifics.new(config, specific_hosts, specific_roles)
+    end
+end

lib/kamal/commander/specifics.rb

@@ -0,0 +1,62 @@
+class Kamal::Commander::Specifics
+  attr_reader :primary_host, :primary_role, :hosts, :roles
+  delegate :stable_sort!, to: Kamal::Utils
+
+  def initialize(config, specific_hosts, specific_roles)
+    @config, @specific_hosts, @specific_roles = config, specific_hosts, specific_roles
+
+    @roles, @hosts = specified_roles, specified_hosts
+
+    @primary_host = specific_hosts&.first || primary_specific_role&.primary_host || config.primary_host
+    @primary_role = primary_or_first_role(roles_on(primary_host))
+
+    stable_sort!(roles) { |role| role == primary_role ? 0 : 1 }
+    sort_primary_role_hosts_first!(hosts)
+  end
+
+  def roles_on(host)
+    roles.select { |role| role.hosts.include?(host.to_s) }
+  end
+
+  def app_hosts
+    @app_hosts ||= sort_primary_role_hosts_first!(config.app_hosts & specified_hosts)
+  end
+
+  def proxy_hosts
+    config.proxy_hosts & specified_hosts
+  end
+
+  def accessory_hosts
+    config.accessories.flat_map(&:hosts) & specified_hosts
+  end
+
+  private
+    attr_reader :config, :specific_hosts, :specific_roles
+
+    def primary_specific_role
+      primary_or_first_role(specific_roles) if specific_roles.present?
+    end
+
+    def primary_or_first_role(roles)
+      roles.detect { |role| role == config.primary_role } || roles.first
+    end
+
+    def specified_roles
+      (specific_roles || config.roles) \
+        .select { |role| ((specific_hosts || config.all_hosts) & role.hosts).any? }
+    end
+
+    def specified_hosts
+      specified_hosts = specific_hosts || config.all_hosts
+
+      if (specific_role_hosts = specific_roles&.flat_map(&:hosts)).present?
+        specified_hosts.select { |host| specific_role_hosts.include?(host) }
+      else
+        specified_hosts
+      end
+    end
+
+    def sort_primary_role_hosts_first!(hosts)
+      stable_sort!(hosts) { |host| roles_on(host).any? { |role| role == primary_role } ? 0 : 1 }
+    end
+end

lib/kamal/commands.rb

@@ -0,0 +1,2 @@
+module Kamal::Commands
+end

lib/kamal/commands/accessory.rb

@@ -0,0 +1,113 @@
+class Kamal::Commands::Accessory < Kamal::Commands::Base
+  include Proxy
+
+  attr_reader :accessory_config
+  delegate :service_name, :image, :hosts, :port, :files, :directories, :cmd,
+           :network_args, :publish_args, :env_args, :volume_args, :label_args, :option_args,
+           :secrets_io, :secrets_path, :env_directory, :proxy, :running_proxy?, :registry,
+           to: :accessory_config
+
+  def initialize(config, name:)
+    super(config)
+    @accessory_config = config.accessory(name)
+  end
+
+  def run(host: nil)
+    docker :run,
+      "--name", service_name,
+      "--detach",
+      "--restart", "unless-stopped",
+      *network_args,
+      *config.logging_args,
+      *publish_args,
+      *([ "--env", "KAMAL_HOST=\"#{host}\"" ] if host),
+      *env_args,
+      *volume_args,
+      *label_args,
+      *option_args,
+      image,
+      cmd
+  end
+
+  def start
+    docker :container, :start, service_name
+  end
+
+  def stop
+    docker :container, :stop, service_name
+  end
+
+  def info(all: false, quiet: false)
+    docker :ps, *("-a" if all), *("-q" if quiet), *service_filter
+  end
+
+  def logs(timestamps: true, since: nil, lines: nil, grep: nil, grep_options: nil)
+    pipe \
+      docker(:logs, service_name, (" --since #{since}" if since), (" --tail #{lines}" if lines), ("--timestamps" if timestamps), "2>&1"),
+      ("grep '#{grep}'#{" #{grep_options}" if grep_options}" if grep)
+  end
+
+  def follow_logs(timestamps: true, grep: nil, grep_options: nil)
+    run_over_ssh \
+      pipe \
+        docker(:logs, service_name, ("--timestamps" if timestamps), "--tail", "10", "--follow", "2>&1"),
+        (%(grep "#{grep}"#{" #{grep_options}" if grep_options}) if grep)
+  end
+
+  def execute_in_existing_container(*command, interactive: false)
+    docker :exec,
+      (docker_interactive_args if interactive),
+      service_name,
+      *command
+  end
+
+  def execute_in_new_container(*command, interactive: false)
+    docker :run,
+      (docker_interactive_args if interactive),
+      "--rm",
+      *network_args,
+      *env_args,
+      *volume_args,
+      image,
+      *command
+  end
+
+  def execute_in_existing_container_over_ssh(*command)
+    run_over_ssh execute_in_existing_container(*command, interactive: true)
+  end
+
+  def execute_in_new_container_over_ssh(*command)
+    run_over_ssh execute_in_new_container(*command, interactive: true)
+  end
+
+  def run_over_ssh(command)
+    super command, host: hosts.first
+  end
+
+  def ensure_local_file_present(local_file)
+    if !local_file.is_a?(StringIO) && !Pathname.new(local_file).exist?
+      raise "Missing file: #{local_file}"
+    end
+  end
+
+  def remove_service_directory
+    [ :rm, "-rf", service_name ]
+  end
+
+  def remove_container
+    docker :container, :prune, "--force", *service_filter
+  end
+
+  def remove_image
+    docker :image, :rm, "--force", image
+  end
+
+  def ensure_env_directory
+    make_directory env_directory
+  end
+
+  private
+    def service_filter
+      [ "--filter", "label=service=#{service_name}" ]
+    end
+end

lib/kamal/commands/accessory/proxy.rb

@@ -0,0 +1,16 @@
+module Kamal::Commands::Accessory::Proxy
+  delegate :container_name, to: :"config.proxy_boot", prefix: :proxy
+
+  def deploy(target:)
+    proxy_exec :deploy, service_name, *proxy.deploy_command_args(target: target)
+  end
+
+  def remove
+    proxy_exec :remove, service_name
+  end
+
+  private
+    def proxy_exec(*command)
+      docker :exec, proxy_container_name, "kamal-proxy", *command
+    end
+end

lib/kamal/commands/app.rb

@@ -0,0 +1,124 @@
+class Kamal::Commands::App < Kamal::Commands::Base
+  include Assets, Containers, ErrorPages, Execution, Images, Logging, Proxy
+
+  ACTIVE_DOCKER_STATUSES = [ :running, :restarting ]
+
+  attr_reader :role, :host
+
+  delegate :container_name, to: :role
+
+  def initialize(config, role: nil, host: nil)
+    super(config)
+    @role = role
+    @host = host
+  end
+
+  def run(hostname: nil)
+    docker :run,
+      "--detach",
+      "--restart unless-stopped",
+      "--name", container_name,
+      "--network", "kamal",
+      *([ "--hostname", hostname ] if hostname),
+      "--env", "KAMAL_CONTAINER_NAME=\"#{container_name}\"",
+      "--env", "KAMAL_VERSION=\"#{config.version}\"",
+      "--env", "KAMAL_HOST=\"#{host}\"",
+      *role.env_args(host),
+      *role.logging_args,
+      *config.volume_args,
+      *role.asset_volume_args,
+      *role.label_args,
+      *role.option_args,
+      config.absolute_image,
+      role.cmd
+  end
+
+  def start
+    docker :start, container_name
+  end
+
+  def status(version:)
+    pipe container_id_for_version(version), xargs(docker(:inspect, "--format", DOCKER_HEALTH_STATUS_FORMAT))
+  end
+
+  def stop(version: nil)
+    pipe \
+      version ? container_id_for_version(version) : current_running_container_id,
+      xargs(docker(:stop, *role.stop_args))
+  end
+
+  def info
+    docker :ps, *container_filter_args
+  end
+
+
+  def current_running_container_id
+    current_running_container(format: "--quiet")
+  end
+
+  def container_id_for_version(version, only_running: false)
+    container_id_for(container_name: container_name(version), only_running: only_running)
+  end
+
+  def current_running_version
+    pipe \
+      current_running_container(format: "--format '{{.Names}}'"),
+      extract_version_from_name
+  end
+
+  def list_versions(*docker_args, statuses: nil)
+    pipe \
+      docker(:ps, *container_filter_args(statuses: statuses), *docker_args, "--format", '"{{.Names}}"'),
+      extract_version_from_name
+  end
+
+  def ensure_env_directory
+    make_directory role.env_directory
+  end
+
+  private
+    def latest_image_id
+      docker :image, :ls, *argumentize("--filter", "reference=#{config.latest_image}"), "--format", "'{{.ID}}'"
+    end
+
+    def current_running_container(format:)
+      pipe \
+        shell(chain(latest_image_container(format: format), latest_container(format: format))),
+        [ :head, "-1" ]
+    end
+
+    def latest_image_container(format:)
+      latest_container format: format, filters: [ "ancestor=$(#{latest_image_id.join(" ")})" ]
+    end
+
+    def latest_container(format:, filters: nil)
+      docker :ps, "--latest", *format, *container_filter_args(statuses: ACTIVE_DOCKER_STATUSES), argumentize("--filter", filters)
+    end
+
+    def container_filter_args(statuses: nil)
+      argumentize "--filter", container_filters(statuses: statuses)
+    end
+
+    def image_filter_args
+      argumentize "--filter", image_filters
+    end
+
+    def extract_version_from_name
+      # Extract SHA from "service-role-dest-SHA"
+      %(while read line; do echo ${line##{role.container_prefix}-}; done)
+    end
+
+    def container_filters(statuses: nil)
+      [ "label=service=#{config.service}" ].tap do |filters|
+        filters << "label=destination=#{config.destination}"
+        filters << "label=role=#{role}" if role
+        statuses&.each do |status|
+          filters << "status=#{status}"
+        end
+      end
+    end
+
+    def image_filters
+      [ "label=service=#{config.service}" ]
+    end
+end

lib/kamal/commands/app/assets.rb

@@ -0,0 +1,51 @@
+module Kamal::Commands::App::Assets
+  def extract_assets
+    asset_container = "#{role.container_prefix}-assets"
+
+    combine \
+      make_directory(role.asset_extracted_directory),
+      [ *docker(:container, :rm, asset_container, "2> /dev/null"), "|| true" ],
+      docker(:container, :create, "--name", asset_container, config.absolute_image),
+      docker(:container, :cp, "-L", "#{asset_container}:#{role.asset_path}/.", role.asset_extracted_directory),
+      docker(:container, :rm, asset_container),
+      by: "&&"
+  end
+
+  def sync_asset_volumes(old_version: nil)
+    new_extracted_path, new_volume_path = role.asset_extracted_directory(config.version), role.asset_volume.host_path
+    if old_version.present?
+      old_extracted_path, old_volume_path = role.asset_extracted_directory(old_version), role.asset_volume(old_version).host_path
+    end
+
+    commands = [ make_directory(new_volume_path), copy_contents(new_extracted_path, new_volume_path) ]
+
+    if old_version.present?
+      commands << copy_contents(new_extracted_path, old_volume_path, continue_on_error: true)
+      commands << copy_contents(old_extracted_path, new_volume_path, continue_on_error: true)
+    end
+
+    chain *commands
+  end
+
+  def clean_up_assets
+    chain \
+      find_and_remove_older_siblings(role.asset_extracted_directory),
+      find_and_remove_older_siblings(role.asset_volume_directory)
+  end
+
+  private
+    def find_and_remove_older_siblings(path)
+      [
+        :find,
+        Pathname.new(path).dirname.to_s,
+        "-maxdepth 1",
+        "-name", "'#{role.name}-*'",
+        "!", "-name", Pathname.new(path).basename.to_s,
+        "-exec rm -rf \"{}\" +"
+      ]
+    end
+
+    def copy_contents(source, destination, continue_on_error: false)
+      [ :cp, "-rnT", "#{source}", destination, *("|| true" if continue_on_error) ]
+    end
+end

lib/kamal/commands/app/containers.rb

@@ -0,0 +1,31 @@
+module Kamal::Commands::App::Containers
+  DOCKER_HEALTH_LOG_FORMAT    = "'{{json .State.Health}}'"
+
+  def list_containers
+    docker :container, :ls, "--all", *container_filter_args
+  end
+
+  def list_container_names
+    [ *list_containers, "--format", "'{{ .Names }}'" ]
+  end
+
+  def remove_container(version:)
+    pipe \
+      container_id_for(container_name: container_name(version)),
+      xargs(docker(:container, :rm))
+  end
+
+  def rename_container(version:, new_version:)
+    docker :rename, container_name(version), container_name(new_version)
+  end
+
+  def remove_containers
+    docker :container, :prune, "--force", *container_filter_args
+  end
+
+  def container_health_log(version:)
+    pipe \
+      container_id_for(container_name: container_name(version)),
+      xargs(docker(:inspect, "--format", DOCKER_HEALTH_LOG_FORMAT))
+  end
+end

lib/kamal/commands/app/error_pages.rb

@@ -0,0 +1,9 @@
+module Kamal::Commands::App::ErrorPages
+  def create_error_pages_directory
+    make_directory(config.proxy_boot.error_pages_directory)
+  end
+
+  def clean_up_error_pages
+    [ :find, config.proxy_boot.error_pages_directory, "-mindepth", "1", "-maxdepth", "1", "!", "-name", KAMAL.config.version, "-exec", "rm", "-rf", "{} +" ]
+  end
+end

lib/kamal/commands/app/execution.rb

@@ -0,0 +1,32 @@
+module Kamal::Commands::App::Execution
+  def execute_in_existing_container(*command, interactive: false, env:)
+    docker :exec,
+      (docker_interactive_args if interactive),
+      *argumentize("--env", env),
+      container_name,
+      *command
+  end
+
+  def execute_in_new_container(*command, interactive: false, detach: false, env:)
+    docker :run,
+      (docker_interactive_args if interactive),
+      ("--detach" if detach),
+      ("--rm" unless detach),
+      "--network", "kamal",
+      *role&.env_args(host),
+      *argumentize("--env", env),
+      *role.logging_args,
+      *config.volume_args,
+      *role&.option_args,
+      config.absolute_image,
+      *command
+  end
+
+  def execute_in_existing_container_over_ssh(*command,  env:)
+    run_over_ssh execute_in_existing_container(*command, interactive: true, env: env), host: host
+  end
+
+  def execute_in_new_container_over_ssh(*command, env:)
+    run_over_ssh execute_in_new_container(*command, interactive: true, env: env), host: host
+  end
+end

lib/kamal/commands/app/images.rb

@@ -0,0 +1,13 @@
+module Kamal::Commands::App::Images
+  def list_images
+    docker :image, :ls, config.repository
+  end
+
+  def remove_images
+    docker :image, :prune, "--all", "--force", *image_filter_args
+  end
+
+  def tag_latest_image
+    docker :tag, config.absolute_image, config.latest_image
+  end
+end

lib/kamal/commands/app/logging.rb

@@ -0,0 +1,28 @@
+module Kamal::Commands::App::Logging
+  def logs(container_id: nil, timestamps: true, since: nil, lines: nil, grep: nil, grep_options: nil)
+    pipe \
+      container_id_command(container_id),
+      "xargs docker logs#{" --timestamps" if timestamps}#{" --since #{since}" if since}#{" --tail #{lines}" if lines} 2>&1",
+      ("grep '#{grep}'#{" #{grep_options}" if grep_options}" if grep)
+  end
+
+  def follow_logs(host:, container_id: nil, timestamps: true, lines: nil, grep: nil, grep_options: nil)
+    run_over_ssh \
+      pipe(
+        container_id_command(container_id),
+        "xargs docker logs#{" --timestamps" if timestamps}#{" --tail #{lines}" if lines} --follow 2>&1",
+        (%(grep "#{grep}"#{" #{grep_options}" if grep_options}) if grep)
+      ),
+      host: host
+  end
+
+  private
+
+  def container_id_command(container_id)
+    case container_id
+    when Array then container_id
+    when String, Symbol then "echo #{container_id}"
+    else current_running_container_id
+    end
+  end
+end

lib/kamal/commands/app/proxy.rb

@@ -0,0 +1,32 @@
+module Kamal::Commands::App::Proxy
+  delegate :container_name, to: :"config.proxy_boot", prefix: :proxy
+
+  def deploy(target:)
+    proxy_exec :deploy, role.container_prefix, *role.proxy.deploy_command_args(target: target)
+  end
+
+  def remove
+    proxy_exec :remove, role.container_prefix
+  end
+
+  def live
+    proxy_exec :resume, role.container_prefix
+  end
+
+  def maintenance(**options)
+    proxy_exec :stop, role.container_prefix, *role.proxy.stop_command_args(**options)
+  end
+
+  def remove_proxy_app_directory
+    remove_directory config.proxy_boot.app_directory
+  end
+
+  def create_ssl_directory
+    make_directory(File.join(config.proxy_boot.tls_directory, role.name))
+  end
+
+  private
+    def proxy_exec(*command)
+      docker :exec, proxy_container_name, "kamal-proxy", *command
+    end
+end

lib/kamal/commands/auditor.rb

@@ -0,0 +1,39 @@
+class Kamal::Commands::Auditor < Kamal::Commands::Base
+  attr_reader :details
+  delegate :escape_shell_value, to: Kamal::Utils
+
+  def initialize(config, **details)
+    super(config)
+    @details = details
+  end
+
+  # Runs remotely
+  def record(line, **details)
+    combine \
+      make_run_directory,
+      append([ :echo, escape_shell_value(audit_line(line, **details)) ], audit_log_file)
+  end
+
+  def reveal
+    [ :tail, "-n", 50, audit_log_file ]
+  end
+
+  private
+    def audit_log_file
+      file = [ config.service, config.destination, "audit.log" ].compact.join("-")
+
+      File.join(config.run_directory, file)
+    end
+
+    def audit_tags(**details)
+      tags(**self.details, **details)
+    end
+
+    def make_run_directory
+      [ :mkdir, "-p", config.run_directory ]
+    end
+
+    def audit_line(line, **details)
+      "#{audit_tags(**details).except(:version, :service_version, :service)} #{line}"
+    end
+end

lib/kamal/commands/base.rb

@@ -0,0 +1,134 @@
+module Kamal::Commands
+  class Base
+    delegate :sensitive, :argumentize, to: Kamal::Utils
+
+    DOCKER_HEALTH_STATUS_FORMAT = "'{{if .State.Health}}{{.State.Health.Status}}{{else}}{{.State.Status}}{{end}}'"
+
+    attr_accessor :config
+
+    def initialize(config)
+      @config = config
+    end
+
+    def run_over_ssh(*command, host:)
+      "ssh#{ssh_proxy_args}#{ssh_keys_args} -t #{config.ssh.user}@#{host} -p #{config.ssh.port} '#{command.join(" ").gsub("'", "'\\\\''")}'"
+    end
+
+    def container_id_for(container_name:, only_running: false)
+      docker :container, :ls, *("--all" unless only_running), "--filter", "name=^#{container_name}$", "--quiet"
+    end
+
+    def make_directory_for(remote_file)
+      make_directory Pathname.new(remote_file).dirname.to_s
+    end
+
+    def make_directory(path)
+      [ :mkdir, "-p", path ]
+    end
+
+    def remove_directory(path)
+      [ :rm, "-r", path ]
+    end
+
+    def remove_file(path)
+      [ :rm, path ]
+    end
+
+    def ensure_docker_installed
+      combine \
+        ensure_local_docker_installed,
+        ensure_local_buildx_installed
+    end
+
+    private
+      def combine(*commands, by: "&&")
+        commands
+          .compact
+          .collect { |command| Array(command) + [ by ] }.flatten # Join commands
+          .tap     { |commands| commands.pop } # Remove trailing combiner
+      end
+
+      def chain(*commands)
+        combine *commands, by: ";"
+      end
+
+      def pipe(*commands)
+        combine *commands, by: "|"
+      end
+
+      def append(*commands)
+        combine *commands, by: ">>"
+      end
+
+      def write(*commands)
+        combine *commands, by: ">"
+      end
+
+      def any(*commands)
+        combine *commands, by: "||"
+      end
+
+      def substitute(*commands)
+        "\$\(#{commands.join(" ")}\)"
+      end
+
+      def xargs(command)
+        [ :xargs, command ].flatten
+      end
+
+      def shell(command)
+        [ :sh, "-c", "'#{command.flatten.join(" ").gsub("'", "'\\\\''")}'" ]
+      end
+
+      def docker(*args)
+        args.compact.unshift :docker
+      end
+
+      def pack(*args)
+        args.compact.unshift :pack
+      end
+
+      def git(*args, path: nil)
+        [ :git, *([ "-C", path ] if path), *args.compact ]
+      end
+
+      def grep(*args)
+        args.compact.unshift :grep
+      end
+
+      def tags(**details)
+        Kamal::Tags.from_config(config, **details)
+      end
+
+      def ssh_proxy_args
+        case config.ssh.proxy
+        when Net::SSH::Proxy::Jump
+          " -J #{config.ssh.proxy.jump_proxies}"
+        when Net::SSH::Proxy::Command
+          " -o ProxyCommand='#{config.ssh.proxy.command_line_template}'"
+        end
+      end
+
+      def ssh_keys_args
+        "#{ ssh_keys.join("") if ssh_keys}" + "#{" -o IdentitiesOnly=yes" if config.ssh&.keys_only}"
+      end
+
+      def ssh_keys
+        config.ssh.keys&.map do |key|
+          " -i #{key}"
+        end
+      end
+
+      def ensure_local_docker_installed
+        docker "--version"
+      end
+
+      def ensure_local_buildx_installed
+        docker :buildx, "version"
+      end
+
+      def docker_interactive_args
+        STDIN.isatty ? "-it" : "-i"
+      end
+  end
+end

lib/kamal/commands/builder.rb

@@ -0,0 +1,48 @@
+require "active_support/core_ext/string/filters"
+
+class Kamal::Commands::Builder < Kamal::Commands::Base
+  delegate :create, :remove, :dev, :push, :clean, :pull, :info, :inspect_builder, :validate_image, :first_mirror, to: :target
+  delegate :local?, :remote?, :pack?, :cloud?, to: "config.builder"
+
+  include Clone
+
+  def name
+    target.class.to_s.remove("Kamal::Commands::Builder::").underscore.inquiry
+  end
+
+  def target
+    if remote?
+      if local?
+        hybrid
+      else
+        remote
+      end
+    elsif pack?
+      pack
+    elsif cloud?
+      cloud
+    else
+      local
+    end
+  end
+
+  def remote
+    @remote ||= Kamal::Commands::Builder::Remote.new(config)
+  end
+
+  def local
+    @local ||= Kamal::Commands::Builder::Local.new(config)
+  end
+
+  def hybrid
+    @hybrid ||= Kamal::Commands::Builder::Hybrid.new(config)
+  end
+
+  def pack
+    @pack ||= Kamal::Commands::Builder::Pack.new(config)
+  end
+
+  def cloud
+    @cloud ||= Kamal::Commands::Builder::Cloud.new(config)
+  end
+end

lib/kamal/commands/builder/base.rb

@@ -0,0 +1,124 @@
+class Kamal::Commands::Builder::Base < Kamal::Commands::Base
+  class BuilderError < StandardError; end
+
+  ENDPOINT_DOCKER_HOST_INSPECT = "'{{.Endpoints.docker.Host}}'"
+
+  delegate :argumentize, to: Kamal::Utils
+  delegate \
+    :args, :secrets, :dockerfile, :target, :arches, :local_arches, :remote_arches, :remote,
+    :pack?, :pack_builder, :pack_buildpacks,
+    :cache_from, :cache_to, :ssh, :provenance, :sbom, :driver, :docker_driver?,
+    to: :builder_config
+
+  def clean
+    docker :image, :rm, "--force", config.absolute_image
+  end
+
+  def push(export_action = "registry", tag_as_dirty: false)
+    docker :buildx, :build,
+      "--output=type=#{export_action}",
+      *platform_options(arches),
+      *([ "--builder", builder_name ] unless docker_driver?),
+      *build_tag_options(tag_as_dirty: tag_as_dirty),
+      *build_options,
+      build_context,
+      "2>&1"
+  end
+
+  def pull
+    docker :pull, config.absolute_image
+  end
+
+  def info
+    combine \
+      docker(:context, :ls),
+      docker(:buildx, :ls)
+  end
+
+  def inspect_builder
+    docker :buildx, :inspect, builder_name unless docker_driver?
+  end
+
+  def build_options
+    [ *build_cache, *build_labels, *build_args, *build_secrets, *build_dockerfile, *build_target, *build_ssh, *builder_provenance, *builder_sbom ]
+  end
+
+  def build_context
+    config.builder.context
+  end
+
+  def validate_image
+    pipe \
+      docker(:inspect, "-f", "'{{ .Config.Labels.service }}'", config.absolute_image),
+      any(
+        [ :grep, "-x", config.service ],
+        "(echo \"Image #{config.absolute_image} is missing the 'service' label\" && exit 1)"
+      )
+  end
+
+  def first_mirror
+    docker(:info, "--format '{{index .RegistryConfig.Mirrors 0}}'")
+  end
+
+  private
+    def build_tag_names(tag_as_dirty: false)
+      tag_names = [ config.absolute_image, config.latest_image ]
+      tag_names.map! { |t| "#{t}-dirty" } if tag_as_dirty
+      tag_names
+    end
+
+    def build_tag_options(tag_as_dirty: false)
+      build_tag_names(tag_as_dirty: tag_as_dirty).flat_map { |name| [ "-t", name ] }
+    end
+
+    def build_cache
+      if cache_to && cache_from
+        [ "--cache-to", cache_to,
+          "--cache-from", cache_from ]
+      end
+    end
+
+    def build_labels
+      argumentize "--label", { service: config.service }
+    end
+
+    def build_args
+      argumentize "--build-arg", args, sensitive: true
+    end
+
+    def build_secrets
+      argumentize "--secret", secrets.keys.collect { |secret| [ "id", secret ] }
+    end
+
+    def build_dockerfile
+      if Pathname.new(File.expand_path(dockerfile)).exist?
+        argumentize "--file", dockerfile
+      else
+        raise BuilderError, "Missing #{dockerfile}"
+      end
+    end
+
+    def build_target
+      argumentize "--target", target if target.present?
+    end
+
+    def build_ssh
+      argumentize "--ssh", ssh if ssh.present?
+    end
+
+    def builder_provenance
+      argumentize "--provenance", provenance unless provenance.nil?
+    end
+
+    def builder_sbom
+      argumentize "--sbom", sbom unless sbom.nil?
+    end
+
+    def builder_config
+      config.builder
+    end
+
+    def platform_options(arches)
+      argumentize "--platform", arches.map { |arch| "linux/#{arch}" }.join(",") if arches.any?
+    end
+end

lib/kamal/commands/builder/clone.rb

@@ -0,0 +1,31 @@
+module Kamal::Commands::Builder::Clone
+  def clone
+    git :clone, escaped_root, "--recurse-submodules", path: config.builder.clone_directory.shellescape
+  end
+
+  def clone_reset_steps
+    [
+      git(:remote, "set-url", :origin, escaped_root, path: escaped_build_directory),
+      git(:fetch, :origin, path: escaped_build_directory),
+      git(:reset, "--hard", Kamal::Git.revision, path: escaped_build_directory),
+      git(:clean, "-fdx", path: escaped_build_directory),
+      git(:submodule, :update, "--init", path: escaped_build_directory)
+    ]
+  end
+
+  def clone_status
+    git :status, "--porcelain", path: escaped_build_directory
+  end
+
+  def clone_revision
+    git :"rev-parse", :HEAD, path: escaped_build_directory
+  end
+
+  def escaped_root
+    Kamal::Git.root.shellescape
+  end
+
+  def escaped_build_directory
+    config.builder.build_directory.shellescape
+  end
+end

lib/kamal/commands/builder/cloud.rb

@@ -0,0 +1,22 @@
+class Kamal::Commands::Builder::Cloud < Kamal::Commands::Builder::Base
+  # Expects `driver` to be of format "cloud docker-org-name/builder-name"
+
+  def create
+    docker :buildx, :create, "--driver", driver
+  end
+
+  def remove
+    docker :buildx, :rm, builder_name
+  end
+
+  private
+    def builder_name
+      driver.gsub(/[ \/]/, "-")
+    end
+
+    def inspect_buildx
+      pipe \
+        docker(:buildx, :inspect, builder_name),
+        grep("-q", "Endpoint:.*cloud://.*")
+    end
+end

lib/kamal/commands/builder/hybrid.rb

@@ -0,0 +1,21 @@
+class Kamal::Commands::Builder::Hybrid < Kamal::Commands::Builder::Remote
+  def create
+    combine \
+      create_local_buildx,
+      create_remote_context,
+      append_remote_buildx
+  end
+
+  private
+    def builder_name
+      "kamal-hybrid-#{driver}-#{remote.gsub(/[^a-z0-9_-]/, "-")}"
+    end
+
+    def create_local_buildx
+      docker :buildx, :create, *platform_options(local_arches), "--name", builder_name, "--driver=#{driver}"
+    end
+
+    def append_remote_buildx
+      docker :buildx, :create, *platform_options(remote_arches), "--append", "--name", builder_name, remote_context_name
+    end
+end

lib/kamal/commands/builder/local.rb

@@ -0,0 +1,14 @@
+class Kamal::Commands::Builder::Local < Kamal::Commands::Builder::Base
+  def create
+    docker :buildx, :create, "--name", builder_name, "--driver=#{driver}" unless docker_driver?
+  end
+
+  def remove
+    docker :buildx, :rm, builder_name unless docker_driver?
+  end
+
+  private
+    def builder_name
+      "kamal-local-#{driver}"
+    end
+end

lib/kamal/commands/builder/pack.rb

@@ -0,0 +1,46 @@
+class Kamal::Commands::Builder::Pack < Kamal::Commands::Builder::Base
+  def push(export_action = "registry")
+    combine \
+      build,
+      export(export_action)
+  end
+
+  def remove;end
+
+  def info
+    pack :builder, :inspect, pack_builder
+  end
+  alias_method :inspect_builder, :info
+
+  private
+    def build
+      pack(:build,
+        config.repository,
+        "--platform", platform,
+        "--creation-time", "now",
+        "--builder", pack_builder,
+        buildpacks,
+        "-t", config.absolute_image,
+        "-t", config.latest_image,
+        "--env", "BP_IMAGE_LABELS=service=#{config.service}",
+        *argumentize("--env", args),
+        *argumentize("--env", secrets, sensitive: true),
+        "--path", build_context)
+    end
+
+    def export(export_action)
+      return unless export_action == "registry"
+
+      combine \
+        docker(:push, config.absolute_image),
+        docker(:push, config.latest_image)
+    end
+
+    def platform
+      "linux/#{local_arches.first}"
+    end
+
+    def buildpacks
+      (pack_buildpacks << "paketo-buildpacks/image-labels").map { |buildpack| [ "--buildpack", buildpack ] }
+    end
+end

lib/kamal/commands/builder/remote.rb

@@ -0,0 +1,63 @@
+class Kamal::Commands::Builder::Remote < Kamal::Commands::Builder::Base
+  def create
+    chain \
+      create_remote_context,
+      create_buildx
+  end
+
+  def remove
+    chain \
+      remove_remote_context,
+      remove_buildx
+  end
+
+  def info
+    chain \
+      docker(:context, :ls),
+      docker(:buildx, :ls)
+  end
+
+  def inspect_builder
+    combine \
+      combine(inspect_buildx, inspect_remote_context),
+      [ "(echo no compatible builder && exit 1)" ],
+      by: "||"
+  end
+
+  private
+    def builder_name
+      "kamal-remote-#{remote.gsub(/[^a-z0-9_-]/, "-")}"
+    end
+
+    def remote_context_name
+      "#{builder_name}-context"
+    end
+
+    def inspect_buildx
+      pipe \
+        docker(:buildx, :inspect, builder_name),
+        grep("-q", "Endpoint:.*#{remote_context_name}")
+    end
+
+    def inspect_remote_context
+      pipe \
+        docker(:context, :inspect, remote_context_name, "--format", ENDPOINT_DOCKER_HOST_INSPECT),
+        grep("-xq", remote)
+    end
+
+    def create_remote_context
+      docker :context, :create, remote_context_name, "--description", "'#{builder_name} host'", "--docker", "'host=#{remote}'"
+    end
+
+    def remove_remote_context
+      docker :context, :rm, remote_context_name
+    end
+
+    def create_buildx
+      docker :buildx, :create, "--name", builder_name, remote_context_name
+    end
+
+    def remove_buildx
+      docker :buildx, :rm, builder_name
+    end
+end

lib/kamal/commands/docker.rb

@@ -0,0 +1,34 @@
+class Kamal::Commands::Docker < Kamal::Commands::Base
+  # Install Docker using the https://github.com/docker/docker-install convenience script.
+  def install
+    pipe get_docker, :sh
+  end
+
+  # Checks the Docker client version. Fails if Docker is not installed.
+  def installed?
+    docker "-v"
+  end
+
+  # Checks the Docker server version. Fails if Docker is not running.
+  def running?
+    docker :version
+  end
+
+  # Do we have superuser access to install Docker and start system services?
+  def superuser?
+    [ '[ "${EUID:-$(id -u)}" -eq 0 ] || command -v sudo >/dev/null || command -v su >/dev/null' ]
+  end
+
+  def create_network
+    docker :network, :create, :kamal
+  end
+
+  private
+    def get_docker
+      shell \
+        any \
+          [ :curl, "-fsSL", "https://get.docker.com" ],
+          [ :wget, "-O -", "https://get.docker.com" ],
+          [ :echo, "\"exit 1\"" ]
+    end
+end

lib/kamal/commands/hook.rb

@@ -0,0 +1,20 @@
+class Kamal::Commands::Hook < Kamal::Commands::Base
+  def run(hook)
+    [ hook_file(hook) ]
+  end
+
+  def env(secrets: false, **details)
+    tags(**details).env.tap do |env|
+      env.merge!(config.secrets.to_h) if secrets
+    end
+  end
+
+  def hook_exists?(hook)
+    Pathname.new(hook_file(hook)).exist?
+  end
+
+  private
+    def hook_file(hook)
+      File.join(config.hooks_path, hook)
+    end
+end

lib/kamal/commands/lock.rb

@@ -0,0 +1,70 @@
+require "active_support/duration"
+require "time"
+require "base64"
+
+class Kamal::Commands::Lock < Kamal::Commands::Base
+  def acquire(message, version)
+    combine \
+      [ :mkdir, lock_dir ],
+      write_lock_details(message, version)
+  end
+
+  def release
+    combine \
+      [ :rm, lock_details_file ],
+      [ :rm, "-r", lock_dir ]
+  end
+
+  def status
+    combine \
+      stat_lock_dir,
+      read_lock_details
+  end
+
+  def ensure_locks_directory
+    [ :mkdir, "-p", locks_dir ]
+  end
+
+  private
+    def write_lock_details(message, version)
+      write \
+        [ :echo, "\"#{Base64.encode64(lock_details(message, version))}\"" ],
+        lock_details_file
+    end
+
+    def read_lock_details
+      pipe \
+        [ :cat, lock_details_file ],
+        [ :base64, "-d" ]
+    end
+
+    def stat_lock_dir
+      write \
+        [ :stat, lock_dir ],
+        "/dev/null"
+    end
+
+    def lock_dir
+      dir_name = [ "lock", config.service, config.destination ].compact.join("-")
+
+      File.join(config.run_directory, dir_name)
+    end
+
+    def lock_details_file
+      File.join(lock_dir, "details")
+    end
+
+    def lock_details(message, version)
+      <<~DETAILS.strip
+        Locked by: #{locked_by} at #{Time.now.utc.iso8601}
+        Version: #{version}
+        Message: #{message}
+      DETAILS
+    end
+
+    def locked_by
+      Kamal::Git.user_name
+    rescue Errno::ENOENT
+      "Unknown"
+    end
+end

lib/kamal/commands/proxy.rb

@@ -0,0 +1,127 @@
+class Kamal::Commands::Proxy < Kamal::Commands::Base
+  delegate :argumentize, :optionize, to: Kamal::Utils
+
+  def run
+    pipe boot_config, xargs(docker_run)
+  end
+
+  def start
+    docker :container, :start, container_name
+  end
+
+  def stop(name: container_name)
+    docker :container, :stop, name
+  end
+
+  def start_or_run
+    combine start, run, by: "||"
+  end
+
+  def info
+    docker :ps, "--filter", "name=^#{container_name}$"
+  end
+
+  def version
+    pipe \
+      docker(:inspect, container_name, "--format '{{.Config.Image}}'"),
+      [ :awk, "-F:", "'{print \$NF}'" ]
+  end
+
+  def logs(timestamps: true, since: nil, lines: nil, grep: nil, grep_options: nil)
+    pipe \
+      docker(:logs, container_name, ("--since #{since}" if since), ("--tail #{lines}" if lines), ("--timestamps" if timestamps), "2>&1"),
+      ("grep '#{grep}'#{" #{grep_options}" if grep_options}" if grep)
+  end
+
+  def follow_logs(host:, timestamps: true, grep: nil, grep_options: nil)
+    run_over_ssh pipe(
+      docker(:logs, container_name, ("--timestamps" if timestamps), "--tail", "10", "--follow", "2>&1"),
+      (%(grep "#{grep}"#{" #{grep_options}" if grep_options}) if grep)
+    ).join(" "), host: host
+  end
+
+  def remove_container
+    docker :container, :prune, "--force", "--filter", "label=org.opencontainers.image.title=kamal-proxy"
+  end
+
+  def remove_image
+    docker :image, :prune, "--all", "--force", "--filter", "label=org.opencontainers.image.title=kamal-proxy"
+  end
+
+  def cleanup_traefik
+    chain \
+      docker(:container, :stop, "traefik"),
+      combine(
+        docker(:container, :prune, "--force", "--filter", "label=org.opencontainers.image.title=Traefik"),
+        docker(:image, :prune, "--all", "--force", "--filter", "label=org.opencontainers.image.title=Traefik")
+      )
+  end
+
+  def ensure_proxy_directory
+    make_directory config.proxy_boot.host_directory
+  end
+
+  def remove_proxy_directory
+    remove_directory config.proxy_boot.host_directory
+  end
+
+  def ensure_apps_config_directory
+    make_directory config.proxy_boot.apps_directory
+  end
+
+  def boot_config
+    [ :echo, "#{substitute(read_boot_options)} #{substitute(read_image)}:#{substitute(read_image_version)} #{substitute(read_run_command)}" ]
+  end
+
+  def read_boot_options
+    read_file(config.proxy_boot.options_file, default: config.proxy_boot.default_boot_options.join(" "))
+  end
+
+  def read_image
+    read_file(config.proxy_boot.image_file, default: config.proxy_boot.image_default)
+  end
+
+  def read_image_version
+    read_file(config.proxy_boot.image_version_file, default: Kamal::Configuration::Proxy::Boot::MINIMUM_VERSION)
+  end
+
+  def read_run_command
+    read_file(config.proxy_boot.run_command_file)
+  end
+
+  def reset_boot_options
+    remove_file config.proxy_boot.options_file
+  end
+
+  def reset_image
+    remove_file config.proxy_boot.image_file
+  end
+
+  def reset_image_version
+    remove_file config.proxy_boot.image_version_file
+  end
+
+  def reset_run_command
+    remove_file config.proxy_boot.run_command_file
+  end
+
+  private
+    def container_name
+      config.proxy_boot.container_name
+    end
+
+    def read_file(file, default: nil)
+      combine [ :cat, file, "2>", "/dev/null" ], [ :echo, "\"#{default}\"" ], by: "||"
+    end
+
+    def docker_run
+      docker \
+        :run,
+        "--name", container_name,
+        "--network", "kamal",
+        "--detach",
+        "--restart", "unless-stopped",
+        "--volume", "kamal-proxy-config:/home/kamal-proxy/.config/kamal-proxy",
+        *config.proxy_boot.apps_volume.docker_args
+    end
+end

lib/kamal/commands/prune.rb

@@ -0,0 +1,38 @@
+require "active_support/duration"
+require "active_support/core_ext/numeric/time"
+
+class Kamal::Commands::Prune < Kamal::Commands::Base
+  def dangling_images
+    docker :image, :prune, "--force", "--filter", "label=service=#{config.service}"
+  end
+
+  def tagged_images
+    pipe \
+      docker(:image, :ls, *service_filter, "--format", "'{{.ID}} {{.Repository}}:{{.Tag}}'"),
+      grep("-v -w \"#{active_image_list}\""),
+      "while read image tag; do docker rmi $tag; done"
+  end
+
+  def app_containers(retain:)
+    pipe \
+      docker(:ps, "-q", "-a", *service_filter, *stopped_containers_filters),
+      "tail -n +#{retain + 1}",
+      "while read container_id; do docker rm $container_id; done"
+  end
+
+  private
+    def stopped_containers_filters
+      [ "created", "exited", "dead" ].flat_map { |status| [ "--filter", "status=#{status}" ] }
+    end
+
+    def active_image_list
+      # Pull the images that are used by any containers
+      # Append repo:latest - to avoid deleting the latest tag
+      # Append repo:<none> - to avoid deleting dangling images that are in use. Unused dangling images are deleted separately
+      "$(docker container ls -a --format '{{.Image}}\\|' --filter label=service=#{config.service} | tr -d '\\n')#{config.latest_image}\\|#{config.repository}:<none>"
+    end
+
+    def service_filter
+      [ "--filter", "label=service=#{config.service}" ]
+    end
+end

lib/kamal/commands/registry.rb

@@ -0,0 +1,16 @@
+class Kamal::Commands::Registry < Kamal::Commands::Base
+  def login(registry_config: nil)
+    registry_config ||= config.registry
+
+    docker :login,
+      registry_config.server,
+      "-u", sensitive(Kamal::Utils.escape_shell_value(registry_config.username)),
+      "-p", sensitive(Kamal::Utils.escape_shell_value(registry_config.password))
+  end
+
+  def logout(registry_config: nil)
+    registry_config ||= config.registry
+
+    docker :logout, registry_config.server
+  end
+end

lib/kamal/commands/server.rb

@@ -0,0 +1,15 @@
+class Kamal::Commands::Server < Kamal::Commands::Base
+  def ensure_run_directory
+    make_directory config.run_directory
+  end
+
+  def remove_app_directory
+    remove_directory config.app_directory
+  end
+
+  def app_directory_count
+    pipe \
+      [ :ls, config.apps_directory ],
+      [ :wc, "-l" ]
+  end
+end

lib/kamal/configuration.rb

@@ -0,0 +1,372 @@
+require "active_support/ordered_options"
+require "active_support/core_ext/string/inquiry"
+require "active_support/core_ext/module/delegation"
+require "active_support/core_ext/hash/keys"
+require "erb"
+require "net/ssh/proxy/jump"
+
+class Kamal::Configuration
+  delegate :service, :image, :labels, :hooks_path, to: :raw_config, allow_nil: true
+  delegate :argumentize, :optionize, to: Kamal::Utils
+
+  attr_reader :destination, :raw_config, :secrets
+  attr_reader :accessories, :aliases, :boot, :builder, :env, :logging, :proxy, :proxy_boot, :servers, :ssh, :sshkit, :registry
+
+  include Validation
+
+  class << self
+    def create_from(config_file:, destination: nil, version: nil)
+      ENV["KAMAL_DESTINATION"] = destination
+
+      raw_config = load_config_files(config_file, *destination_config_file(config_file, destination))
+
+      new raw_config, destination: destination, version: version
+    end
+
+    private
+      def load_config_files(*files)
+        files.inject({}) { |config, file| config.deep_merge! load_config_file(file) }
+      end
+
+      def load_config_file(file)
+        if file.exist?
+          # Newer Psych doesn't load aliases by default
+          load_method = YAML.respond_to?(:unsafe_load) ? :unsafe_load : :load
+          YAML.send(load_method, ERB.new(File.read(file)).result).symbolize_keys
+        else
+          raise "Configuration file not found in #{file}"
+        end
+      end
+
+      def destination_config_file(base_config_file, destination)
+        base_config_file.sub_ext(".#{destination}.yml") if destination
+      end
+  end
+
+  def initialize(raw_config, destination: nil, version: nil, validate: true)
+    @raw_config = ActiveSupport::InheritableOptions.new(raw_config)
+    @destination = destination
+    @declared_version = version
+
+    validate! raw_config, example: validation_yml.symbolize_keys, context: "", with: Kamal::Configuration::Validator::Configuration
+
+    @secrets = Kamal::Secrets.new(destination: destination)
+
+    # Eager load config to validate it, these are first as they have dependencies later on
+    @servers = Servers.new(config: self)
+    @registry = Registry.new(config: @raw_config, secrets: secrets)
+
+    @accessories = @raw_config.accessories&.keys&.collect { |name| Accessory.new(name, config: self) } || []
+    @aliases = @raw_config.aliases&.keys&.to_h { |name| [ name, Alias.new(name, config: self) ] } || {}
+    @boot = Boot.new(config: self)
+    @builder = Builder.new(config: self)
+    @env = Env.new(config: @raw_config.env || {}, secrets: secrets)
+
+    @logging = Logging.new(logging_config: @raw_config.logging)
+    @proxy = Proxy.new(config: self, proxy_config: @raw_config.proxy, secrets: secrets)
+    @proxy_boot = Proxy::Boot.new(config: self)
+    @ssh = Ssh.new(config: self)
+    @sshkit = Sshkit.new(config: self)
+
+    ensure_destination_if_required
+    ensure_required_keys_present
+    ensure_valid_kamal_version
+    ensure_retain_containers_valid
+    ensure_valid_service_name
+    ensure_no_traefik_reboot_hooks
+    ensure_one_host_for_ssl_roles
+    ensure_unique_hosts_for_ssl_roles
+  end
+
+  def version=(version)
+    @declared_version = version
+  end
+
+  def version
+    @declared_version.presence || ENV["VERSION"] || git_version
+  end
+
+  def abbreviated_version
+    if version
+      # Don't abbreviate <sha>_uncommitted_<etc>
+      if version.include?("_")
+        version
+      else
+        version[0...7]
+      end
+    end
+  end
+
+  def minimum_version
+    raw_config.minimum_version
+  end
+
+  def service_and_destination
+    [ service, destination ].compact.join("-")
+  end
+
+  def roles
+    servers.roles
+  end
+
+  def role(name)
+    roles.detect { |r| r.name == name.to_s }
+  end
+
+  def accessory(name)
+    accessories.detect { |a| a.name == name.to_s }
+  end
+
+  def all_hosts
+    (roles + accessories).flat_map(&:hosts).uniq
+  end
+
+  def app_hosts
+    roles.flat_map(&:hosts).uniq
+  end
+
+  def primary_host
+    primary_role&.primary_host
+  end
+
+  def primary_role_name
+    raw_config.primary_role || "web"
+  end
+
+  def primary_role
+    role(primary_role_name)
+  end
+
+  def allow_empty_roles?
+    raw_config.allow_empty_roles
+  end
+
+  def proxy_roles
+    roles.select(&:running_proxy?)
+  end
+
+  def proxy_role_names
+    proxy_roles.flat_map(&:name)
+  end
+
+  def proxy_accessories
+    accessories.select(&:running_proxy?)
+  end
+
+  def proxy_hosts
+    (proxy_roles.flat_map(&:hosts) + proxy_accessories.flat_map(&:hosts)).uniq
+  end
+
+  def repository
+    [ registry.server, image ].compact.join("/")
+  end
+
+  def absolute_image
+    "#{repository}:#{version}"
+  end
+
+  def latest_image
+    "#{repository}:#{latest_tag}"
+  end
+
+  def latest_tag
+    [ "latest", *destination ].join("-")
+  end
+
+  def service_with_version
+    "#{service}-#{version}"
+  end
+
+  def require_destination?
+    raw_config.require_destination
+  end
+
+  def retain_containers
+    raw_config.retain_containers || 5
+  end
+
+  def volume_args
+    if raw_config.volumes.present?
+      argumentize "--volume", raw_config.volumes
+    else
+      []
+    end
+  end
+
+  def logging_args
+    logging.args
+  end
+
+  def readiness_delay
+    raw_config.readiness_delay || 7
+  end
+
+  def deploy_timeout
+    raw_config.deploy_timeout || 30
+  end
+
+  def drain_timeout
+    raw_config.drain_timeout || 30
+  end
+
+  def run_directory
+    ".kamal"
+  end
+
+  def apps_directory
+    File.join run_directory, "apps"
+  end
+
+  def app_directory
+    File.join apps_directory, service_and_destination
+  end
+
+  def env_directory
+    File.join app_directory, "env"
+  end
+
+  def assets_directory
+    File.join app_directory, "assets"
+  end
+
+  def hooks_path
+    raw_config.hooks_path || ".kamal/hooks"
+  end
+
+  def asset_path
+    raw_config.asset_path
+  end
+
+  def error_pages_path
+    raw_config.error_pages_path
+  end
+
+  def env_tags
+    @env_tags ||= if (tags = raw_config.env["tags"])
+      tags.collect { |name, config| Env::Tag.new(name, config: config, secrets: secrets) }
+    else
+      []
+    end
+  end
+
+  def env_tag(name)
+    env_tags.detect { |t| t.name == name.to_s }
+  end
+
+  def to_h
+    {
+      roles: role_names,
+      hosts: all_hosts,
+      primary_host: primary_host,
+      version: version,
+      repository: repository,
+      absolute_image: absolute_image,
+      service_with_version: service_with_version,
+      volume_args: volume_args,
+      ssh_options: ssh.to_h,
+      sshkit: sshkit.to_h,
+      builder: builder.to_h,
+      accessories: raw_config.accessories,
+      logging: logging_args
+    }.compact
+  end
+
+  private
+    # Will raise ArgumentError if any required config keys are missing
+    def ensure_destination_if_required
+      if require_destination? && destination.nil?
+        raise ArgumentError, "You must specify a destination"
+      end
+
+      true
+    end
+
+    def ensure_required_keys_present
+      %i[ service image registry ].each do |key|
+        raise Kamal::ConfigurationError, "Missing required configuration for #{key}" unless raw_config[key].present?
+      end
+
+      if raw_config.servers.nil?
+        raise Kamal::ConfigurationError, "No servers or accessories specified" unless raw_config.accessories.present?
+      else
+        unless role(primary_role_name).present?
+          raise Kamal::ConfigurationError, "The primary_role #{primary_role_name} isn't defined"
+        end
+
+        if primary_role.hosts.empty?
+          raise Kamal::ConfigurationError, "No servers specified for the #{primary_role.name} primary_role"
+        end
+
+        unless allow_empty_roles?
+          roles.each do |role|
+            if role.hosts.empty?
+              raise Kamal::ConfigurationError, "No servers specified for the #{role.name} role. You can ignore this with allow_empty_roles: true"
+            end
+          end
+        end
+      end
+
+      true
+    end
+
+    def ensure_valid_service_name
+      raise Kamal::ConfigurationError, "Service name can only include alphanumeric characters, hyphens, and underscores" unless raw_config[:service] =~ /^[a-z0-9_-]+$/i
+
+      true
+    end
+
+    def ensure_valid_kamal_version
+      if minimum_version && Gem::Version.new(minimum_version) > Gem::Version.new(Kamal::VERSION)
+        raise Kamal::ConfigurationError, "Current version is #{Kamal::VERSION}, minimum required is #{minimum_version}"
+      end
+
+      true
+    end
+
+    def ensure_retain_containers_valid
+      raise Kamal::ConfigurationError, "Must retain at least 1 container" if retain_containers < 1
+
+      true
+    end
+
+    def ensure_no_traefik_reboot_hooks
+      hooks = %w[ pre-traefik-reboot post-traefik-reboot ].select { |hook_file| File.exist?(File.join(hooks_path, hook_file)) }
+
+      if hooks.any?
+        raise Kamal::ConfigurationError, "Found #{hooks.join(", ")}, these should be renamed to (pre|post)-proxy-reboot"
+      end
+
+      true
+    end
+
+    def ensure_one_host_for_ssl_roles
+      roles.each(&:ensure_one_host_for_ssl)
+
+      true
+    end
+
+    def ensure_unique_hosts_for_ssl_roles
+      hosts = roles.select(&:ssl?).flat_map { |role| role.proxy.hosts }
+      duplicates = hosts.tally.filter_map { |host, count| host if count > 1 }
+
+      raise Kamal::ConfigurationError, "Different roles can't share the same host for SSL: #{duplicates.join(", ")}" if duplicates.any?
+
+      true
+    end
+
+    def role_names
+      raw_config.servers.is_a?(Array) ? [ "web" ] : raw_config.servers.keys.sort
+    end
+
+    def git_version
+      @git_version ||=
+        if Kamal::Git.used?
+          if Kamal::Git.uncommitted_changes.present? && !builder.git_clone?
+            uncommitted_suffix = "_uncommitted_#{SecureRandom.hex(8)}"
+          end
+          [ Kamal::Git.revision, uncommitted_suffix ].compact.join
+        else
+          raise "Can't use commit hash as version, no git repository found in #{Dir.pwd}"
+        end
+    end
+end

lib/kamal/configuration/accessory.rb

@@ -0,0 +1,241 @@
+class Kamal::Configuration::Accessory
+  include Kamal::Configuration::Validation
+
+  DEFAULT_NETWORK = "kamal"
+
+  delegate :argumentize, :optionize, to: Kamal::Utils
+
+  attr_reader :name, :env, :proxy, :registry
+
+  def initialize(name, config:)
+    @name, @config, @accessory_config = name.inquiry, config, config.raw_config["accessories"][name]
+
+    validate! \
+      accessory_config,
+      example: validation_yml["accessories"]["mysql"],
+      context: "accessories/#{name}",
+      with: Kamal::Configuration::Validator::Accessory
+
+    ensure_valid_roles
+
+    @env = initialize_env
+    @proxy = initialize_proxy if running_proxy?
+    @registry = initialize_registry if accessory_config["registry"].present?
+  end
+
+  def service_name
+    accessory_config["service"] || "#{config.service}-#{name}"
+  end
+
+  def image
+    [ registry&.server, accessory_config["image"] ].compact.join("/")
+  end
+
+  def hosts
+    hosts_from_host || hosts_from_hosts || hosts_from_roles || hosts_from_tags
+  end
+
+  def port
+    if port = accessory_config["port"]&.to_s
+      port.include?(":") ? port : "#{port}:#{port}"
+    end
+  end
+
+  def network_args
+    argumentize "--network", network
+  end
+
+  def publish_args
+    argumentize "--publish", port if port
+  end
+
+  def labels
+    default_labels.merge(accessory_config["labels"] || {})
+  end
+
+  def label_args
+    argumentize "--label", labels
+  end
+
+  def env_args
+    [ *env.clear_args, *argumentize("--env-file", secrets_path) ]
+  end
+
+  def env_directory
+    File.join(config.env_directory, "accessories")
+  end
+
+  def secrets_io
+    env.secrets_io
+  end
+
+  def secrets_path
+    File.join(config.env_directory, "accessories", "#{name}.env")
+  end
+
+  def files
+    accessory_config["files"]&.to_h do |local_to_remote_mapping|
+      local_file, remote_file = local_to_remote_mapping.split(":")
+      [ expand_local_file(local_file), expand_remote_file(remote_file) ]
+    end || {}
+  end
+
+  def directories
+    accessory_config["directories"]&.to_h do |host_to_container_mapping|
+      host_path, container_path = host_to_container_mapping.split(":")
+      [ expand_host_path(host_path), container_path ]
+    end || {}
+  end
+
+  def volumes
+    specific_volumes + remote_files_as_volumes + remote_directories_as_volumes
+  end
+
+  def volume_args
+    argumentize "--volume", volumes
+  end
+
+  def option_args
+    if args = accessory_config["options"]
+      optionize args
+    else
+      []
+    end
+  end
+
+  def cmd
+    accessory_config["cmd"]
+  end
+
+  def running_proxy?
+    accessory_config["proxy"].present?
+  end
+
+  private
+    attr_reader :config, :accessory_config
+
+    def initialize_env
+      Kamal::Configuration::Env.new \
+        config: accessory_config.fetch("env", {}),
+        secrets: config.secrets,
+        context: "accessories/#{name}/env"
+    end
+
+    def initialize_proxy
+      Kamal::Configuration::Proxy.new \
+        config: config,
+        proxy_config: accessory_config["proxy"],
+        context: "accessories/#{name}/proxy",
+        secrets: config.secrets
+    end
+
+    def initialize_registry
+      Kamal::Configuration::Registry.new \
+        config: accessory_config,
+        secrets: config.secrets,
+        context: "accessories/#{name}/registry"
+    end
+
+    def default_labels
+      { "service" => service_name }
+    end
+
+    def expand_local_file(local_file)
+      if local_file.end_with?("erb")
+        with_clear_env_loaded { read_dynamic_file(local_file) }
+      else
+        Pathname.new(File.expand_path(local_file)).to_s
+      end
+    end
+
+    def with_clear_env_loaded
+      env.clear.each { |k, v| ENV[k] = v }
+      yield
+    ensure
+      env.clear.each { |k, v| ENV.delete(k) }
+    end
+
+    def read_dynamic_file(local_file)
+      StringIO.new(ERB.new(File.read(local_file)).result)
+    end
+
+    def expand_remote_file(remote_file)
+      service_name + remote_file
+    end
+
+    def specific_volumes
+      accessory_config["volumes"] || []
+    end
+
+    def remote_files_as_volumes
+      accessory_config["files"]&.collect do |local_to_remote_mapping|
+        _, remote_file = local_to_remote_mapping.split(":")
+        "#{service_data_directory + remote_file}:#{remote_file}"
+      end || []
+    end
+
+    def remote_directories_as_volumes
+      accessory_config["directories"]&.collect do |host_to_container_mapping|
+        host_path, container_path = host_to_container_mapping.split(":")
+        [ expand_host_path(host_path), container_path ].join(":")
+      end || []
+    end
+
+    def expand_host_path(host_path)
+      absolute_path?(host_path) ? host_path : File.join(service_data_directory, host_path)
+    end
+
+    def absolute_path?(path)
+      Pathname.new(path).absolute?
+    end
+
+    def service_data_directory
+      "$PWD/#{service_name}"
+    end
+
+    def hosts_from_host
+      [ accessory_config["host"] ] if accessory_config.key?("host")
+    end
+
+    def hosts_from_hosts
+      accessory_config["hosts"] if accessory_config.key?("hosts")
+    end
+
+    def hosts_from_roles
+      if accessory_config.key?("role")
+       config.role(accessory_config["role"])&.hosts
+      elsif accessory_config.key?("roles")
+        accessory_config["roles"].flat_map { |role| config.role(role)&.hosts }
+      end
+    end
+
+    def hosts_from_tags
+      if accessory_config.key?("tag")
+        extract_hosts_from_config_with_tag(accessory_config["tag"])
+      elsif accessory_config.key?("tags")
+        accessory_config["tags"].flat_map { |tag| extract_hosts_from_config_with_tag(tag) }
+      end
+    end
+
+    def extract_hosts_from_config_with_tag(tag)
+      if (servers_with_roles = config.raw_config.servers).is_a?(Hash)
+        servers_with_roles.flat_map do |role, servers_in_role|
+          servers_in_role.filter_map do |host|
+            host.keys.first if host.is_a?(Hash) && host.values.first.include?(tag)
+          end
+        end
+      end
+    end
+
+    def network
+      accessory_config["network"] || DEFAULT_NETWORK
+    end
+
+    def ensure_valid_roles
+      if accessory_config["roles"] && (missing_roles = accessory_config["roles"] - config.roles.map(&:name)).any?
+        raise Kamal::ConfigurationError, "accessories/#{name}: unknown roles #{missing_roles.join(", ")}"
+      elsif accessory_config["role"] && !config.role(accessory_config["role"])
+        raise Kamal::ConfigurationError, "accessories/#{name}: unknown role #{accessory_config["role"]}"
+      end
+    end
+end

lib/kamal/configuration/alias.rb

@@ -0,0 +1,15 @@
+class Kamal::Configuration::Alias
+  include Kamal::Configuration::Validation
+
+  attr_reader :name, :command
+
+  def initialize(name, config:)
+    @name, @command = name.inquiry, config.raw_config["aliases"][name]
+
+    validate! \
+      command,
+      example: validation_yml["aliases"]["uname"],
+      context: "aliases/#{name}",
+      with: Kamal::Configuration::Validator::Alias
+  end
+end

lib/kamal/configuration/boot.rb

@@ -0,0 +1,25 @@
+class Kamal::Configuration::Boot
+  include Kamal::Configuration::Validation
+
+  attr_reader :boot_config, :host_count
+
+  def initialize(config:)
+    @boot_config = config.raw_config.boot || {}
+    @host_count = config.all_hosts.count
+    validate! boot_config
+  end
+
+  def limit
+    limit = boot_config["limit"]
+
+    if limit.to_s.end_with?("%")
+      [ host_count * limit.to_i / 100, 1 ].max
+    else
+      limit
+    end
+  end
+
+  def wait
+    boot_config["wait"]
+  end
+end

lib/kamal/configuration/builder.rb

@@ -0,0 +1,211 @@
+class Kamal::Configuration::Builder
+  include Kamal::Configuration::Validation
+
+  attr_reader :config, :builder_config
+  delegate :image, :service, to: :config
+  delegate :server, to: :"config.registry"
+
+  def initialize(config:)
+    @config = config
+    @builder_config = config.raw_config.builder || {}
+    @image = config.image
+    @server = config.registry.server
+    @service = config.service
+
+    validate! builder_config, with: Kamal::Configuration::Validator::Builder
+  end
+
+  def to_h
+    builder_config
+  end
+
+  def remote
+    builder_config["remote"]
+  end
+
+  def arches
+    Array(builder_config.fetch("arch", default_arch))
+  end
+
+  def local_arches
+    @local_arches ||= if local_disabled?
+      []
+    elsif remote
+      arches & [ Kamal::Utils.docker_arch ]
+    else
+      arches
+    end
+  end
+
+  def remote_arches
+    @remote_arches ||= if remote
+      arches - local_arches
+    else
+      []
+    end
+  end
+
+  def remote?
+    remote_arches.any?
+  end
+
+  def local?
+    !local_disabled? && (arches.empty? || local_arches.any?)
+  end
+
+  def cloud?
+    driver.start_with? "cloud"
+  end
+
+  def cached?
+    !!builder_config["cache"]
+  end
+
+  def pack?
+    !!builder_config["pack"]
+  end
+
+  def args
+    builder_config["args"] || {}
+  end
+
+  def secrets
+    (builder_config["secrets"] || []).to_h { |key| [ key, config.secrets[key] ] }
+  end
+
+  def dockerfile
+    builder_config["dockerfile"] || "Dockerfile"
+  end
+
+  def target
+    builder_config["target"]
+  end
+
+  def context
+    builder_config["context"] || "."
+  end
+
+  def driver
+    builder_config.fetch("driver", "docker-container")
+  end
+
+  def pack_builder
+    builder_config["pack"]["builder"] if pack?
+  end
+
+  def pack_buildpacks
+    builder_config["pack"]["buildpacks"] if pack?
+  end
+
+  def local_disabled?
+    builder_config["local"] == false
+  end
+
+  def cache_from
+    if cached?
+      case builder_config["cache"]["type"]
+      when "gha"
+        cache_from_config_for_gha
+      when "registry"
+        cache_from_config_for_registry
+      end
+    end
+  end
+
+  def cache_to
+    if cached?
+      case builder_config["cache"]["type"]
+      when "gha"
+        cache_to_config_for_gha
+      when "registry"
+        cache_to_config_for_registry
+      end
+    end
+  end
+
+  def ssh
+    builder_config["ssh"]
+  end
+
+  def provenance
+    builder_config["provenance"]
+  end
+
+  def sbom
+    builder_config["sbom"]
+  end
+
+  def git_clone?
+    Kamal::Git.used? && builder_config["context"].nil?
+  end
+
+  def clone_directory
+    @clone_directory ||= File.join Dir.tmpdir, "kamal-clones", [ service, pwd_sha ].compact.join("-")
+  end
+
+  def build_directory
+    @build_directory ||=
+      if git_clone?
+        File.join clone_directory, repo_basename, repo_relative_pwd
+      else
+        "."
+      end
+  end
+
+  def docker_driver?
+    driver == "docker"
+  end
+
+  private
+    def valid?
+      if docker_driver?
+        raise ArgumentError, "Invalid builder configuration: the `docker` driver does not not support remote builders" if remote
+        raise ArgumentError, "Invalid builder configuration: the `docker` driver does not not support caching" if cached?
+        raise ArgumentError, "Invalid builder configuration: the `docker` driver does not not support multiple arches" if arches.many?
+      end
+
+      if @options["cache"] && @options["cache"]["type"]
+        raise ArgumentError, "Invalid cache type: #{@options["cache"]["type"]}" unless [ "gha", "registry" ].include?(@options["cache"]["type"])
+      end
+    end
+
+    def cache_image
+      builder_config["cache"]&.fetch("image", nil) || "#{image}-build-cache"
+    end
+
+    def cache_image_ref
+      [ server, cache_image ].compact.join("/")
+    end
+
+    def cache_from_config_for_gha
+      "type=gha"
+    end
+
+    def cache_from_config_for_registry
+      [ "type=registry", "ref=#{cache_image_ref}" ].compact.join(",")
+    end
+
+    def cache_to_config_for_gha
+      [ "type=gha", builder_config["cache"]&.fetch("options", nil) ].compact.join(",")
+    end
+
+    def cache_to_config_for_registry
+      [ "type=registry", "ref=#{cache_image_ref}", builder_config["cache"]&.fetch("options", nil) ].compact.join(",")
+    end
+
+    def repo_basename
+      File.basename(Kamal::Git.root)
+    end
+
+    def repo_relative_pwd
+      Dir.pwd.delete_prefix(Kamal::Git.root)
+    end
+
+    def pwd_sha
+      Digest::SHA256.hexdigest(Dir.pwd)[0..12]
+    end
+
+    def default_arch
+      docker_driver? ? [] : [ "amd64", "arm64" ]
+    end
+end

lib/kamal/configuration/docs/accessory.yml

@@ -0,0 +1,128 @@
+# Accessories
+#
+# Accessories can be booted on a single host, a list of hosts, or on specific roles.
+# The hosts do not need to be defined in the Kamal servers configuration.
+#
+# Accessories are managed separately from the main service — they are not updated
+# when you deploy, and they do not have zero-downtime deployments.
+#
+# Run `kamal accessory boot <accessory>` to boot an accessory.
+# See `kamal accessory --help` for more information.
+
+# Configuring accessories
+#
+# First, define the accessory in the `accessories`:
+accessories:
+  mysql:
+
+    # Service name
+    #
+    # This is used in the service label and defaults to `<service>-<accessory>`,
+    # where `<service>` is the main service name from the root configuration:
+    service: mysql
+
+    # Image
+    #
+    # The Docker image to use.
+    # Prefix it with its server when using root level registry different from Docker Hub.
+    # Define registry directly or via anchors when it differs from root level registry.
+    image: mysql:8.0
+
+    # Registry
+    #
+    # By default accessories use Docker Hub registry.
+    # You can specify different registry per accessory with this option.
+    # Don't prefix image with this registry server.
+    # Use anchors if you need to set the same specific registry for several accessories.
+    #
+    # ```yml
+    # registry:
+    #   <<: *specific-registry
+    # ```
+    #
+    # See kamal docs registry for more information:
+    registry:
+      ...
+
+    # Accessory hosts
+    #
+    # Specify one of `host`, `hosts`, `role`, `roles`, `tag` or `tags`:
+    host: mysql-db1
+    hosts:
+      - mysql-db1
+      - mysql-db2
+    role: mysql
+    roles:
+      - mysql
+    tag: writer
+    tags:
+      - writer
+      - reader
+
+    # Custom command
+    #
+    # You can set a custom command to run in the container if you do not want to use the default:
+    cmd: "bin/mysqld"
+
+    # Port mappings
+    #
+    # See [https://docs.docker.com/network/](https://docs.docker.com/network/), and
+    # especially note the warning about the security implications of exposing ports publicly.
+    port: "127.0.0.1:3306:3306"
+
+    # Labels
+    labels:
+      app: myapp
+
+    # Options
+    #
+    # These are passed to the Docker run command in the form `--<name> <value>`:
+    options:
+      restart: always
+      cpus: 2
+
+    # Environment variables
+    #
+    # See kamal docs env for more information:
+    env:
+      ...
+
+    # Copying files
+    #
+    # You can specify files to mount into the container.
+    # The format is `local:remote`, where `local` is the path to the file on the local machine
+    # and `remote` is the path to the file in the container.
+    #
+    # They will be uploaded from the local repo to the host and then mounted.
+    #
+    # ERB files will be evaluated before being copied.
+    files:
+      - config/my.cnf.erb:/etc/mysql/my.cnf
+      - config/myoptions.cnf:/etc/mysql/myoptions.cnf
+
+    # Directories
+    #
+    # You can specify directories to mount into the container. They will be created on the host
+    # before being mounted:
+    directories:
+      - mysql-logs:/var/log/mysql
+
+    # Volumes
+    #
+    # Any other volumes to mount, in addition to the files and directories.
+    # They are not created or copied before mounting:
+    volumes:
+      - /path/to/mysql-logs:/var/log/mysql
+
+    # Network
+    #
+    # The network the accessory will be attached to.
+    #
+    # Defaults to kamal:
+    network: custom
+
+    # Proxy
+    #
+    # You can run your accessory behind the Kamal proxy. See kamal docs proxy for more information
+    proxy:
+      ...

lib/kamal/configuration/docs/alias.yml

@@ -0,0 +1,26 @@
+# Aliases
+#
+# Aliases are shortcuts for Kamal commands.
+#
+# For example, for a Rails app, you might open a console with:
+#
+# ```shell
+# kamal app exec -i --reuse "bin/rails console"
+# ```
+#
+# By defining an alias, like this:
+aliases:
+  console: app exec -i --reuse "bin/rails console"
+# You can now open the console with:
+#
+# ```shell
+# kamal console
+# ```
+
+# Configuring aliases
+#
+# Aliases are defined in the root config under the alias key.
+#
+# Each alias is named and can only contain lowercase letters, numbers, dashes, and underscores:
+aliases:
+  uname: app exec -p -q -r web "uname -a"

lib/kamal/configuration/docs/boot.yml

@@ -0,0 +1,19 @@
+# Booting
+#
+# When deploying to large numbers of hosts, you might prefer not to restart your services on every host at the same time.
+#
+# Kamal’s default is to boot new containers on all hosts in parallel. However, you can control this with the boot configuration.
+
+# Fixed group sizes
+#
+# Here, we boot 2 hosts at a time with a 10-second gap between each group:
+boot:
+  limit: 2
+  wait: 10
+
+# Percentage of hosts
+#
+# Here, we boot 25% of the hosts at a time with a 2-second gap between each group:
+boot:
+  limit: 25%
+  wait: 2

lib/kamal/configuration/docs/builder.yml

@@ -0,0 +1,132 @@
+# Builder
+#
+# The builder configuration controls how the application is built with `docker build`.
+#
+# See https://kamal-deploy.org/docs/configuration/builder-examples/ for more information.
+
+# Builder options
+#
+# Options go under the builder key in the root configuration.
+builder:
+
+  # Arch
+  #
+  # The architectures to build for — you can set an array or just a single value.
+  #
+  # Allowed values are `amd64` and `arm64`:
+  arch:
+    - amd64
+
+  # Remote
+  #
+  # The connection string for a remote builder. If supplied, Kamal will use this
+  # for builds that do not match the local architecture of the deployment host.
+  remote: ssh://docker@docker-builder
+
+  # Local
+  #
+  # If set to false, Kamal will always use the remote builder even when building
+  # the local architecture.
+  #
+  # Defaults to true:
+  local: true
+
+  # Buildpack configuration
+  #
+  # The build configuration for using pack to build a Cloud Native Buildpack image.
+  #
+  # For additional buildpack customization options you can create a project descriptor
+  # file(project.toml) that the Pack CLI will automatically use.
+  # See https://buildpacks.io/docs/for-app-developers/how-to/build-inputs/use-project-toml/ for more information.
+  pack:
+    builder: heroku/builder:24
+    buildpacks:
+      - heroku/ruby
+      - heroku/procfile
+
+  # Builder cache
+  #
+  # The type must be either 'gha' or 'registry'.
+  #
+  # The image is only used for registry cache and is not compatible with the Docker driver:
+  cache:
+    type: registry
+    options: mode=max
+    image: kamal-app-build-cache
+
+  # Build context
+  #
+  # If this is not set, then a local Git clone of the repo is used.
+  # This ensures a clean build with no uncommitted changes.
+  #
+  # To use the local checkout instead, you can set the context to `.`, or a path to another directory.
+  context: .
+
+  # Dockerfile
+  #
+  # The Dockerfile to use for building, defaults to `Dockerfile`:
+  dockerfile: Dockerfile.production
+
+  # Build target
+  #
+  # If not set, then the default target is used:
+  target: production
+
+  # Build arguments
+  #
+  # Any additional build arguments, passed to `docker build` with `--build-arg <key>=<value>`:
+  args:
+    ENVIRONMENT: production
+
+  # Referencing build arguments
+  #
+  # ```shell
+  # ARG RUBY_VERSION
+  # FROM ruby:$RUBY_VERSION-slim as base
+  # ```
+
+  # Build secrets
+  #
+  # Values are read from `.kamal/secrets`:
+  secrets:
+    - SECRET1
+    - SECRET2
+
+  # Referencing build secrets
+  #
+  # ```shell
+  # # Copy Gemfiles
+  # COPY Gemfile Gemfile.lock ./
+  #
+  # # Install dependencies, including private repositories via access token
+  # # Then remove bundle cache with exposed GITHUB_TOKEN
+  # RUN --mount=type=secret,id=GITHUB_TOKEN \
+  #   BUNDLE_GITHUB__COM=x-access-token:$(cat /run/secrets/GITHUB_TOKEN) \
+  #   bundle install && \
+  #   rm -rf /usr/local/bundle/cache
+  # ```
+
+  # SSH
+  #
+  # SSH agent socket or keys to expose to the build:
+  ssh: default=$SSH_AUTH_SOCK
+
+  # Driver
+  #
+  # The build driver to use, defaults to `docker-container`:
+  driver: docker
+  #
+  # If you want to use Docker Build Cloud (https://www.docker.com/products/build-cloud/), you can set the driver to:
+  driver: cloud org-name/builder-name
+
+  # Provenance
+  #
+  # It is used to configure provenance attestations for the build result.
+  # The value can also be a boolean to enable or disable provenance attestations.
+  provenance: mode=max
+
+  # SBOM (Software Bill of Materials)
+  #
+  # It is used to configure SBOM generation for the build result.
+  # The value can also be a boolean to enable or disable SBOM generation.
+  sbom: true

lib/kamal/configuration/docs/configuration.yml

@@ -0,0 +1,184 @@
+# Kamal Configuration
+#
+# Configuration is read from the `config/deploy.yml`.
+
+# Destinations
+#
+# When running commands, you can specify a destination with the `-d` flag,
+# e.g., `kamal deploy -d staging`.
+#
+# In this case, the configuration will also be read from `config/deploy.staging.yml`
+# and merged with the base configuration.
+
+# Extensions
+#
+# Kamal will not accept unrecognized keys in the configuration file.
+#
+# However, you might want to declare a configuration block using YAML anchors
+# and aliases to avoid repetition.
+#
+# You can prefix a configuration section with `x-` to indicate that it is an
+# extension. Kamal will ignore the extension and not raise an error.
+
+# The service name
+#
+# This is a required value. It is used as the container name prefix.
+service: myapp
+
+# The Docker image name
+#
+# The image will be pushed to the configured registry.
+image: my-image
+
+# Labels
+#
+# Additional labels to add to the container:
+labels:
+  my-label: my-value
+
+# Volumes
+#
+# Additional volumes to mount into the container:
+volumes:
+  - /path/on/host:/path/in/container:ro
+
+# Registry
+#
+# The Docker registry configuration, see kamal docs registry:
+registry:
+  ...
+
+# Servers
+#
+# The servers to deploy to, optionally with custom roles, see kamal docs servers:
+servers:
+  ...
+
+# Environment variables
+#
+# See kamal docs env:
+env:
+  ...
+
+# Asset path
+#
+# Used for asset bridging across deployments, default to `nil`.
+#
+# If there are changes to CSS or JS files, we may get requests
+# for the old versions on the new container, and vice versa.
+#
+# To avoid 404s, we can specify an asset path.
+# Kamal will replace that path in the container with a mapped
+# volume containing both sets of files.
+# This requires that file names change when the contents change
+# (e.g., by including a hash of the contents in the name).
+#
+# To configure this, set the path to the assets:
+asset_path: /path/to/assets
+
+# Hooks path
+#
+# Path to hooks, defaults to `.kamal/hooks`.
+# See https://kamal-deploy.org/docs/hooks for more information:
+hooks_path: /user_home/kamal/hooks
+
+# Error pages
+#
+# A directory relative to the app root to find error pages for the proxy to serve.
+# Any files in the format 4xx.html or 5xx.html will be copied to the hosts.
+error_pages_path: public
+
+# Require destinations
+#
+# Whether deployments require a destination to be specified, defaults to `false`:
+require_destination: true
+
+# Primary role
+#
+# This defaults to `web`, but if you have no web role, you can change this:
+primary_role: workers
+
+# Allowing empty roles
+#
+# Whether roles with no servers are allowed. Defaults to `false`:
+allow_empty_roles: false
+
+# Retain containers
+#
+# How many old containers and images we retain, defaults to 5:
+retain_containers: 3
+
+# Minimum version
+#
+# The minimum version of Kamal required to deploy this configuration, defaults to `nil`:
+minimum_version: 1.3.0
+
+# Readiness delay
+#
+# Seconds to wait for a container to boot after it is running, default 7.
+#
+# This only applies to containers that do not run a proxy or specify a healthcheck:
+readiness_delay: 4
+
+# Deploy timeout
+#
+# How long to wait for a container to become ready, default 30:
+deploy_timeout: 10
+
+# Drain timeout
+#
+# How long to wait for a container to drain, default 30:
+drain_timeout: 10
+
+# Run directory
+#
+# Directory to store kamal runtime files in on the host, default `.kamal`:
+run_directory: /etc/kamal
+
+# SSH options
+#
+# See kamal docs ssh:
+ssh:
+  ...
+
+# Builder options
+#
+# See kamal docs builder:
+builder:
+  ...
+
+# Accessories
+#
+# Additional services to run in Docker, see kamal docs accessory:
+accessories:
+  ...
+
+# Proxy
+#
+# Configuration for kamal-proxy, see kamal docs proxy:
+proxy:
+  ...
+
+# SSHKit
+#
+# See kamal docs sshkit:
+sshkit:
+  ...
+
+# Boot options
+#
+# See kamal docs boot:
+boot:
+  ...
+
+# Logging
+#
+# Docker logging configuration, see kamal docs logging:
+logging:
+  ...
+
+# Aliases
+#
+# Alias configuration, see kamal docs alias:
+aliases:
+  ...

lib/kamal/configuration/docs/env.yml

@@ -0,0 +1,116 @@
+# Environment variables
+#
+# Environment variables can be set directly in the Kamal configuration or
+# read from `.kamal/secrets`.
+
+# Reading environment variables from the configuration
+#
+# Environment variables can be set directly in the configuration file.
+#
+# These are passed to the `docker run` command when deploying.
+env:
+  DATABASE_HOST: mysql-db1
+  DATABASE_PORT: 3306
+
+# Secrets
+#
+# Kamal uses dotenv to automatically load environment variables set in the `.kamal/secrets` file.
+#
+# If you are using destinations, secrets will instead be read from `.kamal/secrets.<DESTINATION>` if
+# it exists.
+#
+# Common secrets across all destinations can be set in `.kamal/secrets-common`.
+#
+# This file can be used to set variables like `KAMAL_REGISTRY_PASSWORD` or database passwords.
+# You can use variable or command substitution in the secrets file.
+#
+# ```shell
+# KAMAL_REGISTRY_PASSWORD=$KAMAL_REGISTRY_PASSWORD
+# RAILS_MASTER_KEY=$(cat config/master.key)
+# ```
+#
+# You can also use [secret helpers](../../commands/secrets) for some common password managers.
+#
+# ```shell
+# SECRETS=$(kamal secrets fetch ...)
+#
+# REGISTRY_PASSWORD=$(kamal secrets extract REGISTRY_PASSWORD $SECRETS)
+# DB_PASSWORD=$(kamal secrets extract DB_PASSWORD $SECRETS)
+# ```
+#
+# If you store secrets directly in `.kamal/secrets`, ensure that it is not checked into version control.
+#
+# To pass the secrets, you should list them under the `secret` key. When you do this, the
+# other variables need to be moved under the `clear` key.
+#
+# Unlike clear values, secrets are not passed directly to the container
+# but are stored in an env file on the host:
+env:
+  clear:
+    DB_USER: app
+  secret:
+    - DB_PASSWORD
+
+# Aliased secrets
+#
+# You can also alias secrets to other secrets using a `:` separator.
+#
+# This is useful when the ENV name is different from the secret name. For example, if you have two
+# places where you need to define the ENV variable `DB_PASSWORD`, but the value is different depending
+# on the context.
+#
+# ```shell
+# SECRETS=$(kamal secrets fetch ...)
+#
+# MAIN_DB_PASSWORD=$(kamal secrets extract MAIN_DB_PASSWORD $SECRETS)
+# SECONDARY_DB_PASSWORD=$(kamal secrets extract SECONDARY_DB_PASSWORD $SECRETS)
+# ```
+env:
+  secret:
+    - DB_PASSWORD:MAIN_DB_PASSWORD
+  tags:
+    secondary_db:
+      secret:
+        - DB_PASSWORD:SECONDARY_DB_PASSWORD
+accessories:
+  main_db_accessory:
+    env:
+      secret:
+        - DB_PASSWORD:MAIN_DB_PASSWORD
+  secondary_db_accessory:
+    env:
+      secret:
+        - DB_PASSWORD:SECONDARY_DB_PASSWORD
+
+# Tags
+#
+# Tags are used to add extra env variables to specific hosts.
+# See kamal docs servers for how to tag hosts.
+#
+# Tags are only allowed in the top-level env configuration (i.e., not under a role-specific env).
+#
+# The env variables can be specified with secret and clear values as explained above.
+env:
+  tags:
+    <tag1>:
+      MYSQL_USER: monitoring
+    <tag2>:
+      clear:
+        MYSQL_USER: readonly
+      secret:
+        - MYSQL_PASSWORD
+
+# Example configuration
+env:
+  clear:
+    MYSQL_USER: app
+  secret:
+    - MYSQL_PASSWORD
+  tags:
+    monitoring:
+      MYSQL_USER: monitoring
+    replica:
+      clear:
+        MYSQL_USER: readonly
+      secret:
+        - READONLY_PASSWORD

lib/kamal/configuration/docs/logging.yml

@@ -0,0 +1,21 @@
+# Custom logging configuration
+#
+# Set these to control the Docker logging driver and options.
+
+# Logging settings
+#
+# These go under the logging key in the configuration file.
+#
+# This can be specified at the root level or for a specific role.
+logging:
+
+  # Driver
+  #
+  # The logging driver to use, passed to Docker via `--log-driver`:
+  driver: json-file
+
+  # Options
+  #
+  # Any logging options to pass to the driver, passed to Docker via `--log-opt`:
+  options:
+    max-size: 100m

lib/kamal/configuration/docs/proxy.yml

@@ -0,0 +1,164 @@
+# Proxy
+#
+# Kamal uses [kamal-proxy](https://github.com/basecamp/kamal-proxy) to provide
+# gapless deployments. It runs on ports 80 and 443 and forwards requests to the
+# application container.
+#
+# The proxy is configured in the root configuration under `proxy`. These are
+# options that are set when deploying the application, not when booting the proxy.
+#
+# They are application-specific, so they are not shared when multiple applications
+# run on the same proxy.
+#
+proxy:
+
+  # Hosts
+  #
+  # The hosts that will be used to serve the app. The proxy will only route requests
+  # to this host to your app.
+  #
+  # If no hosts are set, then all requests will be forwarded, except for matching
+  # requests for other apps deployed on that server that do have a host set.
+  #
+  # Specify one of `host` or `hosts`.
+  host: foo.example.com
+  hosts:
+    - foo.example.com
+    - bar.example.com
+
+  # App port
+  #
+  # The port the application container is exposed on.
+  #
+  # Defaults to 80:
+  app_port: 3000
+
+  # SSL
+  #
+  # kamal-proxy can provide automatic HTTPS for your application via Let's Encrypt.
+  #
+  # This requires that we are deploying to one server and the host option is set.
+  # The host value must point to the server we are deploying to, and port 443 must be
+  # open for the Let's Encrypt challenge to succeed.
+  #
+  # If you set `ssl` to `true`, `kamal-proxy` will stop forwarding headers to your app,
+  # unless you explicitly set `forward_headers: true`
+  #
+  # Defaults to `false`:
+  ssl: true
+
+  # Custom SSL certificate
+  #
+  # In some cases, using Let's Encrypt for automatic certificate management is not an
+  # option, for example if you are running from more than one host.
+  #
+  # Or you may already have SSL certificates issued by a different Certificate Authority (CA).
+  #
+  # Kamal supports loading custom SSL certificates directly from secrets. You should
+  # pass a hash mapping the `certificate_pem` and `private_key_pem` to the secret names.
+  ssl:
+    certificate_pem: CERTIFICATE_PEM
+    private_key_pem: PRIVATE_KEY_PEM
+  # ### Notes
+  # - If the certificate or key is missing or invalid, deployments will fail.
+  # - Always handle SSL certificates and private keys securely. Avoid hard-coding them in source control.
+
+  # SSL redirect
+  #
+  # By default, kamal-proxy will redirect all HTTP requests to HTTPS when SSL is enabled.
+  # If you prefer that HTTP traffic is passed through to your application (along with
+  # HTTPS traffic), you can disable this redirect by setting `ssl_redirect: false`:
+  ssl_redirect: false
+
+  # Forward headers
+  #
+  # Whether to forward the `X-Forwarded-For` and `X-Forwarded-Proto` headers.
+  #
+  # If you are behind a trusted proxy, you can set this to `true` to forward the headers.
+  #
+  # By default, kamal-proxy will not forward the headers if the `ssl` option is set to `true`, and
+  # will forward them if it is set to `false`.
+  forward_headers: true
+
+  # Response timeout
+  #
+  # How long to wait for requests to complete before timing out, defaults to 30 seconds:
+  response_timeout: 10
+
+  # Path-based routing
+  #
+  # For applications that split their traffic to different services based on the request path,
+  # you can use path-based routing to mount services under different path prefixes.
+  path_prefix: '/api'
+  # By default, the path prefix will be stripped from the request before it is forwarded upstream.
+  # So in the example above, a request to /api/users/123 will be forwarded to web-1 as /users/123.
+  # To instead forward the request with the original path (including the prefix),
+  # specify --strip-path-prefix=false
+  strip_path_prefix: false
+
+  # Healthcheck
+  #
+  # When deploying, the proxy will by default hit `/up` once every second until we hit
+  # the deploy timeout, with a 5-second timeout for each request.
+  #
+  # Once the app is up, the proxy will stop hitting the healthcheck endpoint.
+  healthcheck:
+    interval: 3
+    path: /health
+    timeout: 3
+
+  # Buffering
+  #
+  # Whether to buffer request and response bodies in the proxy.
+  #
+  # By default, buffering is enabled with a max request body size of 1GB and no limit
+  # for response size.
+  #
+  # You can also set the memory limit for buffering, which defaults to 1MB; anything
+  # larger than that is written to disk.
+  buffering:
+    requests: true
+    responses: true
+    max_request_body: 40_000_000
+    max_response_body: 0
+    memory: 2_000_000
+
+  # Logging
+  #
+  # Configure request logging for the proxy.
+  # You can specify request and response headers to log.
+  # By default, `Cache-Control`, `Last-Modified`, and `User-Agent` request headers are logged:
+  logging:
+    request_headers:
+      - Cache-Control
+      - X-Forwarded-Proto
+    response_headers:
+      - X-Request-ID
+      - X-Request-Start
+
+# Enabling/disabling the proxy on roles
+#
+# The proxy is enabled by default on the primary role but can be disabled by
+# setting `proxy: false` in the primary role's configuration.
+#
+# ```yaml
+# servers:
+#   web:
+#     hosts:
+#      - ...
+#     proxy: false
+# ```
+#
+# It is disabled by default on all other roles but can be enabled by setting
+# `proxy: true` or providing a proxy configuration for that role.
+#
+# ```yaml
+# servers:
+#   web:
+#     hosts:
+#      - ...
+#   web2:
+#     hosts:
+#      - ...
+#     proxy: true
+# ```

lib/kamal/configuration/docs/registry.yml

@@ -0,0 +1,56 @@
+# Registry
+#
+# The default registry is Docker Hub, but you can change it using `registry/server`.
+#
+# By default, Docker Hub creates public repositories. To avoid making your images public,
+# set up a private repository before deploying, or change the default repository privacy
+# settings to private in your [Docker Hub settings](https://hub.docker.com/repository-settings/default-privacy).
+#
+# A reference to a secret (in this case, `DOCKER_REGISTRY_TOKEN`) will look up the secret
+# in the local environment:
+registry:
+  server: registry.digitalocean.com
+  username:
+    - DOCKER_REGISTRY_TOKEN
+  password:
+    - DOCKER_REGISTRY_TOKEN
+
+# Using AWS ECR as the container registry
+#
+# You will need to have the AWS CLI installed locally for this to work.
+# AWS ECR’s access token is only valid for 12 hours. In order to avoid having to manually regenerate the token every time, you can use ERB in the `deploy.yml` file to shell out to the AWS CLI command and obtain the token:
+registry:
+  server: <your aws account id>.dkr.ecr.<your aws region id>.amazonaws.com
+  username: AWS
+  password: <%= %x(aws ecr get-login-password) %>
+
+# Using GCP Artifact Registry as the container registry
+#
+# To sign into Artifact Registry, you need to
+# [create a service account](https://cloud.google.com/iam/docs/service-accounts-create#creating)
+# and [set up roles and permissions](https://cloud.google.com/artifact-registry/docs/access-control#permissions).
+# Normally, assigning the `roles/artifactregistry.writer` role should be sufficient.
+#
+# Once the service account is ready, you need to generate and download a JSON key and base64 encode it:
+#
+# ```shell
+# base64 -i /path/to/key.json | tr -d "\\n"
+# ```
+#
+# You'll then need to set the `KAMAL_REGISTRY_PASSWORD` secret to that value.
+#
+# Use the environment variable as the password along with `_json_key_base64` as the username.
+# Here’s the final configuration:
+registry:
+  server: <your registry region>-docker.pkg.dev
+  username: _json_key_base64
+  password:
+    - KAMAL_REGISTRY_PASSWORD
+
+# Validating the configuration
+#
+# You can validate the configuration by running:
+#
+# ```shell
+# kamal registry login
+# ```

lib/kamal/configuration/docs/role.yml

@@ -0,0 +1,53 @@
+# Roles
+#
+# Roles are used to configure different types of servers in the deployment.
+# The most common use for this is to run web servers and job servers.
+#
+# Kamal expects there to be a `web` role, unless you set a different `primary_role`
+# in the root configuration.
+
+# Role configuration
+#
+# Roles are specified under the servers key:
+servers:
+
+  # Simple role configuration
+  #
+  # This can be a list of hosts if you don't need custom configuration for the role.
+  #
+  # You can set tags on the hosts for custom env variables (see kamal docs env):
+  web:
+    - 172.1.0.1
+    - 172.1.0.2: experiment1
+    - 172.1.0.2: [ experiment1, experiment2 ]
+
+  # Custom role configuration
+  #
+  # When there are other options to set, the list of hosts goes under the `hosts` key.
+  #
+  # By default, only the primary role uses a proxy.
+  #
+  # For other roles, you can set it to `proxy: true` to enable it and inherit the root proxy
+  # configuration or provide a map of options to override the root configuration.
+  #
+  # For the primary role, you can set `proxy: false` to disable the proxy.
+  #
+  # You can also set a custom `cmd` to run in the container and overwrite other settings
+  # from the root configuration.
+  workers:
+    hosts:
+      - 172.1.0.3
+      - 172.1.0.4: experiment1
+    cmd: "bin/jobs"
+    options:
+      memory: 2g
+      cpus: 4
+    logging:
+      ...
+    proxy:
+      ...
+    labels:
+      my-label: workers
+    env:
+      ...
+    asset_path: /public

lib/kamal/configuration/docs/servers.yml

@@ -0,0 +1,27 @@
+# Servers
+#
+# Servers are split into different roles, with each role having its own configuration.
+#
+# For simpler deployments, though, where all servers are identical, you can just specify a list of servers.
+# They will be implicitly assigned to the `web` role.
+servers:
+  - 172.0.0.1
+  - 172.0.0.2
+  - 172.0.0.3
+
+# Tagging servers
+#
+# Servers can be tagged, with the tags used to add custom env variables (see kamal docs env).
+servers:
+  - 172.0.0.1
+  - 172.0.0.2: experiments
+  - 172.0.0.3: [ experiments, three ]
+
+# Roles
+#
+# For more complex deployments (e.g., if you are running job hosts), you can specify roles and configure each separately (see kamal docs role):
+servers:
+  web:
+    ...
+  workers:
+    ...

lib/kamal/configuration/docs/ssh.yml

@@ -0,0 +1,70 @@
+# SSH configuration
+#
+# Kamal uses SSH to connect and run commands on your hosts.
+# By default, it will attempt to connect to the root user on port 22.
+#
+# If you are using a non-root user, you may need to bootstrap your servers manually before using them with Kamal. On Ubuntu, you’d do:
+#
+# ```shell
+# sudo apt update
+# sudo apt upgrade -y
+# sudo apt install -y docker.io curl git
+# sudo usermod -a -G docker app
+# ```
+
+# SSH options
+#
+# The options are specified under the ssh key in the configuration file.
+ssh:
+
+  # The SSH user
+  #
+  # Defaults to `root`:
+  user: app
+
+  # The SSH port
+  #
+  # Defaults to 22:
+  port: "2222"
+
+  # Proxy host
+  #
+  # Specified in the form <host> or <user>@<host>:
+  proxy: root@proxy-host
+
+  # Proxy command
+  #
+  # A custom proxy command, required for older versions of SSH:
+  proxy_command: "ssh -W %h:%p user@proxy"
+
+  # Log level
+  #
+  # Defaults to `fatal`. Set this to `debug` if you are having SSH connection issues.
+  log_level: debug
+
+  # Keys only
+  #
+  # Set to `true` to use only private keys from the `keys` and `key_data` parameters,
+  # even if ssh-agent offers more identities. This option is intended for
+  # situations where ssh-agent offers many different identities or you
+  # need to overwrite all identities and force a single one.
+  keys_only: false
+
+  # Keys
+  #
+  # An array of file names of private keys to use for public key
+  # and host-based authentication:
+  keys: [ "~/.ssh/id.pem" ]
+
+  # Key data
+  #
+  # An array of strings, with each element of the array being
+  # a raw private key in PEM format.
+  key_data: [ "-----BEGIN OPENSSH PRIVATE KEY-----" ]
+
+  # Config
+  #
+  # Set to true to load the default OpenSSH config files (~/.ssh/config,
+  # /etc/ssh_config), to false ignore config files, or to a file path
+  # (or array of paths) to load specific configuration. Defaults to true.
+  config: true

lib/kamal/configuration/docs/sshkit.yml

@@ -0,0 +1,23 @@
+# SSHKit
+#
+# [SSHKit](https://github.com/capistrano/sshkit) is the SSH toolkit used by Kamal.
+#
+# The default, settings should be sufficient for most use cases, but
+# when connecting to a large number of hosts, you may need to adjust.
+
+# SSHKit options
+#
+# The options are specified under the sshkit key in the configuration file.
+sshkit:
+
+  # Max concurrent starts
+  #
+  # Creating SSH connections concurrently can be an issue when deploying to many servers.
+  # By default, Kamal will limit concurrent connection starts to 30 at a time.
+  max_concurrent_starts: 10
+
+  # Pool idle timeout
+  #
+  # Kamal sets a long idle timeout of 900 seconds on connections to try to avoid
+  # re-connection storms after an idle period, such as building an image or waiting for CI.
+  pool_idle_timeout: 300

lib/kamal/configuration/env.rb

@@ -0,0 +1,38 @@
+class Kamal::Configuration::Env
+  include Kamal::Configuration::Validation
+
+  attr_reader :context, :clear, :secret_keys
+  delegate :argumentize, to: Kamal::Utils
+
+  def initialize(config:, secrets:, context: "env")
+    @clear = config.fetch("clear", config.key?("secret") || config.key?("tags") ? {} : config)
+    @secrets = secrets
+    @secret_keys = config.fetch("secret", [])
+    @context = context
+    validate! config, context: context, with: Kamal::Configuration::Validator::Env
+  end
+
+  def clear_args
+    argumentize("--env", clear)
+  end
+
+  def secrets_io
+    Kamal::EnvFile.new(aliased_secrets).to_io
+  end
+
+  def merge(other)
+    self.class.new \
+      config: { "clear" => clear.merge(other.clear), "secret" => secret_keys | other.secret_keys },
+      secrets: @secrets
+  end
+
+  private
+    def aliased_secrets
+      secret_keys.to_h { |key| extract_alias(key) }.transform_values { |secret_key| @secrets[secret_key] }
+    end
+
+    def extract_alias(key)
+      key_name, key_aliased_to = key.split(":", 2)
+      [ key_name, key_aliased_to || key_name ]
+    end
+end

lib/kamal/configuration/env/tag.rb

@@ -0,0 +1,13 @@
+class Kamal::Configuration::Env::Tag
+  attr_reader :name, :config, :secrets
+
+  def initialize(name, config:, secrets:)
+    @name = name
+    @config = config
+    @secrets = secrets
+  end
+
+  def env
+    Kamal::Configuration::Env.new(config: config, secrets: secrets)
+  end
+end

lib/kamal/configuration/logging.rb

@@ -0,0 +1,33 @@
+class Kamal::Configuration::Logging
+  delegate :optionize, :argumentize, to: Kamal::Utils
+
+  include Kamal::Configuration::Validation
+
+  attr_reader :logging_config
+
+  def initialize(logging_config:, context: "logging")
+    @logging_config = logging_config || {}
+    validate! @logging_config, context: context
+  end
+
+  def driver
+    logging_config["driver"]
+  end
+
+  def options
+    logging_config.fetch("options", {})
+  end
+
+  def merge(other)
+    self.class.new logging_config: logging_config.deep_merge(other.logging_config)
+  end
+
+  def args
+    if driver.present? || options.present?
+      optionize({ "log-driver" => driver }.compact) +
+        argumentize("--log-opt", options)
+    else
+      argumentize("--log-opt", { "max-size" => "10m" })
+    end
+  end
+end

lib/kamal/configuration/proxy.rb

@@ -0,0 +1,124 @@
+class Kamal::Configuration::Proxy
+  include Kamal::Configuration::Validation
+
+  DEFAULT_LOG_REQUEST_HEADERS = [ "Cache-Control", "Last-Modified", "User-Agent" ]
+  CONTAINER_NAME = "kamal-proxy"
+
+  delegate :argumentize, :optionize, to: Kamal::Utils
+
+  attr_reader :config, :proxy_config, :role_name, :secrets
+
+  def initialize(config:, proxy_config:, role_name: nil, secrets:, context: "proxy")
+    @config = config
+    @proxy_config = proxy_config
+    @proxy_config = {} if @proxy_config.nil?
+    @role_name = role_name
+    @secrets = secrets
+    validate! @proxy_config, with: Kamal::Configuration::Validator::Proxy, context: context
+  end
+
+  def app_port
+    proxy_config.fetch("app_port", 80)
+  end
+
+  def ssl?
+    proxy_config.fetch("ssl", false)
+  end
+
+  def hosts
+    proxy_config["hosts"] || proxy_config["host"]&.split(",") || []
+  end
+
+  def custom_ssl_certificate?
+    ssl = proxy_config["ssl"]
+    return false unless ssl.is_a?(Hash)
+    ssl["certificate_pem"].present? && ssl["private_key_pem"].present?
+  end
+
+  def certificate_pem_content
+    ssl = proxy_config["ssl"]
+    return nil unless ssl.is_a?(Hash)
+    secrets[ssl["certificate_pem"]]
+  end
+
+  def private_key_pem_content
+    ssl = proxy_config["ssl"]
+    return nil unless ssl.is_a?(Hash)
+    secrets[ssl["private_key_pem"]]
+  end
+
+  def host_tls_cert
+    tls_path(config.proxy_boot.tls_directory, "cert.pem")
+  end
+
+  def host_tls_key
+    tls_path(config.proxy_boot.tls_directory, "key.pem")
+  end
+
+  def container_tls_cert
+    tls_path(config.proxy_boot.tls_container_directory, "cert.pem")
+  end
+
+  def container_tls_key
+    tls_path(config.proxy_boot.tls_container_directory, "key.pem") if custom_ssl_certificate?
+  end
+
+  def deploy_options
+    {
+      host: hosts,
+      tls: ssl? ? true : nil,
+      "tls-certificate-path": container_tls_cert,
+      "tls-private-key-path": container_tls_key,
+      "deploy-timeout": seconds_duration(config.deploy_timeout),
+      "drain-timeout": seconds_duration(config.drain_timeout),
+      "health-check-interval": seconds_duration(proxy_config.dig("healthcheck", "interval")),
+      "health-check-timeout": seconds_duration(proxy_config.dig("healthcheck", "timeout")),
+      "health-check-path": proxy_config.dig("healthcheck", "path"),
+      "target-timeout": seconds_duration(proxy_config["response_timeout"]),
+      "buffer-requests": proxy_config.fetch("buffering", { "requests": true }).fetch("requests", true),
+      "buffer-responses": proxy_config.fetch("buffering", { "responses": true }).fetch("responses", true),
+      "buffer-memory": proxy_config.dig("buffering", "memory"),
+      "max-request-body": proxy_config.dig("buffering", "max_request_body"),
+      "max-response-body": proxy_config.dig("buffering", "max_response_body"),
+      "path-prefix": proxy_config.dig("path_prefix"),
+      "strip-path-prefix": proxy_config.dig("strip_path_prefix"),
+      "forward-headers": proxy_config.dig("forward_headers"),
+      "tls-redirect": proxy_config.dig("ssl_redirect"),
+      "log-request-header": proxy_config.dig("logging", "request_headers") || DEFAULT_LOG_REQUEST_HEADERS,
+      "log-response-header": proxy_config.dig("logging", "response_headers"),
+      "error-pages": error_pages
+    }.compact
+  end
+
+  def deploy_command_args(target:)
+    optionize ({ target: "#{target}:#{app_port}" }).merge(deploy_options), with: "="
+  end
+
+  def stop_options(drain_timeout: nil, message: nil)
+    {
+      "drain-timeout": seconds_duration(drain_timeout),
+      message: message
+    }.compact
+  end
+
+  def stop_command_args(**options)
+    optionize stop_options(**options), with: "="
+  end
+
+  def merge(other)
+    self.class.new config: config, proxy_config: other.proxy_config.deep_merge(proxy_config), role_name: role_name, secrets: secrets
+  end
+
+  private
+    def tls_path(directory, filename)
+      File.join([ directory, role_name, filename ].compact) if custom_ssl_certificate?
+    end
+
+    def seconds_duration(value)
+      value ? "#{value}s" : nil
+    end
+
+    def error_pages
+      File.join config.proxy_boot.error_pages_container_directory, config.version if config.error_pages_path
+    end
+end