Examples¶

Learn Mooncake through practical, hands-on examples. This page contains all examples from beginner to advanced, organized as a step-by-step learning path.

Running Examples¶

All examples are in the examples/ directory of the repository:

# Clone the repo
git clone https://github.com/alehatsman/mooncake.git
cd mooncake

# Run an example
mooncake run --config examples/01-hello-world/config.yml

Beginner Examples¶

01 - Hello World¶

Start here! This is the simplest possible Mooncake configuration.

What You'll Learn¶

Running basic shell commands
Using global system variables
Multi-line shell commands

Quick Start¶

cd examples/01-hello-world
mooncake run --config config.yml

What It Does¶

Prints a hello message
Runs system commands to show OS info
Uses Mooncake's global variables to display OS and architecture

Key Concepts¶

Shell Commands

Execute commands with the shell action:

- name: Print message
  shell: echo "Hello!"

Multi-line Commands

Use | for multiple commands:

- name: Multiple commands
  shell: |
    echo "First command"
    echo "Second command"

Global Variables

Mooncake automatically provides system information: - {{os}} - Operating system (linux, darwin, windows) - {{arch}} - Architecture (amd64, arm64, etc.)

Output Example¶

▶ Print hello message
Hello from Mooncake!
✓ Print hello message

▶ Print system info
OS: Darwin
Arch: arm64
✓ Print system info

▶ Show global variables
Running on darwin/arm64
✓ Show global variables

02 - Variables and System Facts¶

Learn how to define custom variables and use Mooncake's comprehensive system facts.

What You'll Learn¶

Defining custom variables with vars
Using all available system facts
Combining custom variables with system facts
Using variables in file operations

Quick Start¶

cd examples/02-variables-and-facts
mooncake run --config config.yml

What It Does¶

Defines custom application variables
Displays all system facts (OS, hardware, network, software)
Creates files using both custom variables and system facts

Key Concepts¶

Custom Variables

Define your own variables:

- vars:
    app_name: MyApp
    version: "1.0.0"
    environment: development

Use them in commands and paths:

- shell: echo "Running {{app_name}} v{{version}}"

System Facts

Mooncake automatically collects system information:

Category	Variable	Description
Basic	`os`, `arch`, `hostname`, `user_home`	System basics
Hardware	`cpu_cores`, `memory_total_mb`	Hardware info
Distribution	`distribution`, `distribution_version`, `distribution_major`	OS distribution
Software	`package_manager`, `python_version`	Installed software
Network	`ip_addresses`, `ip_addresses_string`	Network info

Variable Substitution

Variables work everywhere:

- file:
    path: "/tmp/{{app_name}}-{{version}}-{{os}}"
    state: directory

Seeing All Facts

Run mooncake explain to see all facts for your system:

mooncake explain

03 - Files and Directories¶

Learn how to create and manage files and directories with Mooncake.

What You'll Learn¶

Creating directories with state: directory
Creating files with state: file
Setting file permissions with mode
Adding content to files

Quick Start¶

cd examples/03-files-and-directories
mooncake run --config config.yml

What It Does¶

Creates application directory structure
Creates files with specific content
Sets appropriate permissions (755 for directories, 644 for files)
Creates executable scripts

Key Concepts¶

Creating Directories

- name: Create directory
  file:
    path: /tmp/myapp
    state: directory
    mode: "0755"  # rwxr-xr-x

Creating Empty Files

- name: Create empty file
  file:
    path: /tmp/file.txt
    state: file
    mode: "0644"  # rw-r--r--

Creating Files with Content

- name: Create config file
  file:
    path: /tmp/config.txt
    state: file
    content: |
      Line 1
      Line 2
    mode: "0644"

File Permissions

Mode	Meaning	Use Case
0755	rwxr-xr-x	Directories, executable scripts
0644	rw-r--r--	Regular files, configs
0600	rw-------	Private files, secrets
0700	rwx------	Private directories

04 - Conditionals¶

Learn how to conditionally execute steps based on system properties or variables.

What You'll Learn¶

Using when for conditional execution
OS and architecture detection
Complex conditions with logical operators
Combining conditionals with tags

Quick Start¶

cd examples/04-conditionals

# Run all steps (only matching conditions will execute)
mooncake run --config config.yml

# Run only dev-tagged steps
mooncake run --config config.yml --tags dev

What It Does¶

Demonstrates steps that always run
Shows OS-specific steps (macOS vs Linux)
Shows architecture-specific steps
Demonstrates tag filtering

Key Concepts¶

Basic Conditionals

Use when to conditionally execute steps:

- name: Linux only
  shell: echo "Running on Linux"
  when: os == "linux"

Available System Variables

os - darwin, linux, windows
arch - amd64, arm64, 386, etc.
distribution - ubuntu, debian, centos, macos, etc.
distribution_major - major version number
package_manager - apt, yum, brew, pacman, etc.

Comparison Operators

== - equals
!= - not equals
>, <, >=, <= - comparisons
&& - logical AND
|| - logical OR
! - logical NOT

Complex Conditions

- name: ARM Mac only
  shell: echo "ARM-based macOS"
  when: os == "darwin" && arch == "arm64"

- name: High memory systems
  shell: echo "Lots of RAM!"
  when: memory_total_mb >= 16000

- name: Ubuntu 20+
  shell: apt update
  when: distribution == "ubuntu" && distribution_major >= "20"

Tags vs Conditionals

Conditionals (when): Evaluated at runtime based on system facts
Tags: User-controlled filtering via CLI --tags flag

Intermediate Examples¶

05 - Templates¶

Learn how to render configuration files from templates using pongo2 syntax.

What You'll Learn¶

Rendering .j2 template files
Using variables in templates
Template conditionals ({% if %})
Template loops ({% for %})
Passing additional vars to templates

Quick Start¶

cd examples/05-templates
mooncake run --config config.yml

# Check the rendered files
ls -lh /tmp/mooncake-templates/
cat /tmp/mooncake-templates/config.yml

What It Does¶

Defines variables for application, server, and database config
Renders application config with loops and conditionals
Renders nginx config with optional SSL
Creates executable script from template
Renders same template with different variables

Key Concepts¶

Template Action

- name: Render config
  template:
    src: ./templates/config.yml.j2
    dest: /tmp/config.yml
    mode: "0644"

Template Syntax (pongo2)

Variables:

{{ variable_name }}
{{ nested.property }}

Conditionals:

{% if debug %}
  debug: true
{% else %}
  debug: false
{% endif %}

Loops:

{% for item in items %}
  - {{ item }}
{% endfor %}

Filters:

{{ path | expanduser }}  # Expands ~ to home directory
{{ text | upper }}       # Convert to uppercase

Passing Additional Vars

Override variables for specific templates:

- template:
    src: ./templates/config.yml.j2
    dest: /tmp/prod-config.yml
    vars:
      environment: production
      debug: false

Common Use Cases

Config files (app.yml, nginx.conf, etc.)
Shell scripts (deployment, setup)
Systemd units (service files)
Dotfiles (.bashrc, .vimrc with customization)

06 - Loops¶

Learn how to iterate over lists and files to avoid repetition.

What You'll Learn¶

Iterating over lists with with_items
Iterating over files with with_filetree
Using the {{ item }} variable
Accessing file properties in loops

Quick Start¶

cd examples/06-loops

# Run list iteration example
mooncake run --config with-items.yml

# Run file tree iteration example
mooncake run --config with-filetree/config.yml

Examples Included¶

1. with-items.yml - List Iteration

Iterate over lists of items:

- vars:
    packages:
      - neovim
      - ripgrep
      - fzf

- name: Install package
  shell: brew install {{ item }}
  with_items: "{{ packages }}"

2. with-filetree/ - File Tree Iteration

Iterate over files in a directory:

- name: Copy dotfile
  shell: cp "{{ item.src }}" "/tmp/backup/{{ item.name }}"
  with_filetree: ./files

Key Concepts¶

List Iteration (with_items)

- vars:
    users: [alice, bob, charlie]

- name: Create user directory
  file:
    path: "/home/{{ item }}"
    state: directory
  with_items: "{{ users }}"

This creates /home/alice, /home/bob, /home/charlie

File Tree Iteration (with_filetree)

- name: Process file
  shell: echo "Processing {{ item.name }}"
  with_filetree: ./dotfiles
  when: item.is_dir == false

Available properties:

item.src - Full source path
item.name - File name
item.is_dir - Boolean, true if directory

Filtering in Loops

Skip directories:

- name: Copy files only
  shell: cp "{{ item.src }}" "/tmp/{{ item.name }}"
  with_filetree: ./files
  when: item.is_dir == false

Real-World Use Cases

with_items:

Installing multiple packages
Creating multiple users/groups
Setting up multiple services

with_filetree:

Managing dotfiles
Deploying configuration directories
Backing up files

07 - Register¶

Learn how to capture command output and use it in subsequent steps.

What You'll Learn¶

Capturing output with register
Accessing stdout, stderr, and return codes
Using captured data in conditionals
Detecting if operations made changes

Quick Start¶

cd examples/07-register
mooncake run --config config.yml

What It Does¶

Checks if git is installed and captures the result
Uses return code to conditionally show messages
Captures username and uses it in file paths
Captures OS version and displays it
Detects if file operations made changes

Key Concepts¶

Basic Registration

- name: Check if git exists
  shell: which git
  register: git_check

- name: Use the result
  shell: echo "Git is at {{ git_check.stdout }}"
  when: git_check.rc == 0

Available Fields

For shell commands:

register_name.stdout - Standard output
register_name.stderr - Standard error
register_name.rc - Return/exit code (0 = success)
register_name.failed - Boolean, true if rc != 0
register_name.changed - Boolean, always true for shell

For file operations:

register_name.rc - 0 for success, 1 for failure
register_name.failed - Boolean
register_name.changed - Boolean, true if file created/modified

Using in Conditionals

- shell: test -f /tmp/file.txt
  register: file_check

- shell: echo "File exists"
  when: file_check.rc == 0

- shell: echo "File not found"
  when: file_check.rc != 0

Using in Templates

- shell: whoami
  register: current_user

- file:
    path: "/tmp/{{ current_user.stdout }}_config.txt"
    state: file
    content: "User: {{ current_user.stdout }}"

Change Detection

- file:
    path: /tmp/test.txt
    state: file
    content: "test"
  register: result

- shell: echo "File was created or modified"
  when: result.changed == true

Common Patterns

Checking for command existence:

- shell: which docker
  register: docker_check

- shell: echo "Docker not installed"
  when: docker_check.rc != 0

Conditional installation:

- shell: python3 --version
  register: python_check

- shell: apt install python3
  become: true
  when: python_check.rc != 0

Advanced Examples¶

08 - Tags¶

Learn how to use tags to selectively run parts of your configuration.

What You'll Learn¶

Adding tags to steps
Filtering execution with --tags flag
Organizing workflows with tags
Combining tags with conditionals

Quick Start¶

cd examples/08-tags

# Run all steps (no tag filter)
mooncake run --config config.yml

# Run only development steps
mooncake run --config config.yml --tags dev

# Run only production steps
mooncake run --config config.yml --tags prod

# Run multiple tag categories
mooncake run --config config.yml --tags dev,test

What It Does¶

Demonstrates different tagged workflows:

Development setup
Production deployment
Testing
Security audits
Staging deployment

Key Concepts¶

Adding Tags

- name: Install dev tools
  shell: echo "Installing tools"
  tags:
    - dev
    - tools

Tag Filtering Behavior

No tags specified: All steps run (including untagged steps)
Tags specified (--tags dev): Only steps with matching tags run
Multiple tags (--tags dev,prod): Steps run if they have ANY of the specified tags (OR logic)

Tag Organization Strategies

By Environment:

tags: [dev, staging, prod]

By Phase:

tags: [setup, deploy, test, cleanup]

By Component:

tags: [database, webserver, cache]

By Role:

tags: [install, configure, security]

Multiple Tags Per Step

- name: Security audit
  shell: run-security-scan
  tags:
    - test
    - prod
    - security

This runs with --tags test, --tags prod, or --tags security

Combining Tags and Conditionals

- name: Install Linux dev tools
  shell: apt install build-essential
  become: true
  when: os == "linux"
  tags:
    - dev
    - tools

Both must match: 1. Condition must be true (os == "linux") 2. Tag must match (if --tags specified)

Best Practices

Use consistent naming - Pick a scheme and stick to it
Multiple tags per step - Makes filtering more flexible
Document your tags - In README or comments
Combine with conditionals - For environment + OS filtering

09 - Sudo / Privilege Escalation¶

Learn how to execute commands and operations with elevated privileges.

What You'll Learn¶

Using become: true for sudo operations
Providing sudo password via CLI
System-level operations
OS-specific privileged operations

Quick Start¶

cd examples/09-sudo

# Requires sudo password
mooncake run --config config.yml --sudo-pass <your-password>

# Preview what would run with sudo
mooncake run --config config.yml --sudo-pass <password> --dry-run

⚠️ Warning: This example contains commands that require root privileges. Review the config before running!

What It Does¶

Runs regular command (no sudo)
Runs privileged command with sudo
Updates package list (Linux)
Installs system packages
Creates system directories and files

Key Concepts¶

Basic Sudo

Add become: true to run with sudo:

- name: System operation
  shell: apt update
  become: true

Providing Password

Three ways to provide sudo password:

Command line (recommended):

mooncake run --config config.yml --sudo-pass mypassword

Environment variable:

export MOONCAKE_SUDO_PASS=mypassword
mooncake run --config config.yml

Which Operations Need Sudo?

Typically require sudo:

Package management (apt, yum, dnf)
System file operations (/etc, /opt, /usr/local)
Service management (systemctl)
User/group management
Mounting filesystems
Network configuration

Don't require sudo:

User-space operations
Home directory files
/tmp directory
Homebrew on macOS (usually)

File Operations with Sudo

- name: Create system directory
  file:
    path: /opt/myapp
    state: directory
    mode: "0755"
  become: true

OS-Specific Sudo

# Linux package management
- name: Install package (Linux)
  shell: apt install -y curl
  become: true
  when: os == "linux" and package_manager == "apt"

# macOS typically doesn't need sudo for homebrew
- name: Install package (macOS)
  shell: brew install curl
  when: os == "darwin"

Security Considerations

Review before running - Check what commands will execute with sudo
Use dry-run - Preview with --dry-run first
Minimize sudo usage - Only use on steps that require it
Specific commands - Don't use become: true on untrusted commands
Password handling - Be careful with password in shell history

10 - Multi-File Configurations¶

Learn how to organize large configurations into multiple files.

What You'll Learn¶

Splitting configuration into multiple files
Using include to load other configs
Using include_vars to load variables
Organizing by environment (dev/prod)
Organizing by platform (Linux/macOS)
Relative path resolution

Quick Start¶

cd examples/10-multi-file-configs

# Run with development environment (default)
mooncake run --config main.yml

# Run with specific tags
mooncake run --config main.yml --tags install

Directory Structure¶

10-multi-file-configs/
├── main.yml              # Entry point
├── tasks/                # Modular task files
│   ├── common.yml        # Common setup
│   ├── linux.yml         # Linux-specific
│   ├── macos.yml         # macOS-specific
│   └── dev-tools.yml     # Development tools
└── vars/                 # Environment variables
    ├── development.yml   # Dev settings
    └── production.yml    # Prod settings

What It Does¶

Sets project variables
Loads environment-specific variables
Runs common setup tasks
Runs OS-specific tasks (Linux or macOS)
Conditionally runs dev tools setup

Key Concepts¶

Entry Point (main.yml)

- vars:
    project_name: MyProject
    env: development

- name: Load environment variables
  include_vars: ./vars/{{env}}.yml

- name: Setup common configuration
  include: ./tasks/common.yml

- name: Setup OS-specific configuration
  include: ./tasks/macos.yml
  when: os == "darwin"

Including Variable Files

- name: Load development vars
  include_vars: ./vars/development.yml

Including Task Files

- name: Run common setup
  include: ./tasks/common.yml

Relative Path Resolution

Paths are relative to the current file, not the working directory:

main.yml:
  include: ./tasks/common.yml  # Relative to main.yml

tasks/common.yml:
  template:
    src: ./templates/config.j2  # Relative to common.yml

Organization Strategies

By Environment:

vars/
  development.yml
  staging.yml
  production.yml

By Platform:

tasks/
  linux.yml
  macos.yml
  windows.yml

By Component:

tasks/
  database.yml
  webserver.yml
  cache.yml

By Phase:

tasks/
  00-prepare.yml
  01-install.yml
  02-configure.yml
  03-deploy.yml

Benefits of Multi-File Organization

Maintainability - Easier to find and update specific parts
Reusability - Share tasks across projects
Collaboration - Team members can work on different files
Testing - Test components independently
Clarity - Clear separation of concerns

11 - Shell Execution Control¶

Learn advanced execution control for shell commands with timeouts, retries, environment variables, and custom result evaluation.

Important: These features are shell-specific and don't apply to file, template, or include operations.

What You'll Learn¶

Setting command timeouts
Retrying failed commands
Configuring retry delays
Setting environment variables
Changing working directory
Custom change detection with changed_when
Custom failure detection with failed_when
Running as different users with become_user

Quick Start¶

cd examples/11-execution-control
mooncake run --config config.yml

Key Concepts¶

Timeouts

Prevent commands from running indefinitely:

- name: Command with timeout
  shell: ./slow-script.sh
  timeout: 30s

Retries

Automatically retry failed operations:

- name: Download file
  shell: curl -O https://example.com/file.tar.gz
  retries: 3
  retry_delay: 5s

Environment Variables

Set custom environment for commands:

- name: Build with custom env
  shell: make build
  env:
    CC: gcc-11
    CFLAGS: "-O2"

Working Directory

Execute commands in specific directories:

- name: Build project
  shell: npm run build
  cwd: /opt/myproject

Custom Change Detection

Override when a step counts as "changed":

- name: Git pull
  shell: git pull
  changed_when: "'Already up to date' not in result.stdout"

Custom Failure Detection

Override when a step is considered failed:

- name: Grep with acceptable exit codes
  shell: grep "pattern" file.txt
  failed_when: "result.rc >= 2"  # 0=found, 1=not found, 2+=error

Different Users

Run commands as specific users:

- name: Run as postgres
  shell: psql -c "SELECT version()"
  become: true
  become_user: postgres

Real-World Example¶

Robust service deployment with retries and validation:

- name: Download release
  shell: curl -O https://releases.example.com/app-{{version}}.tar.gz
  timeout: 10m
  retries: 3
  retry_delay: 30s

- name: Install application
  shell: pip install -r requirements.txt
  cwd: /opt/myapp
  become: true
  become_user: appuser
  timeout: 5m
  env:
    PIP_INDEX_URL: "{{pip_mirror}}"

- name: Run migrations
  shell: ./manage.py migrate
  cwd: /opt/myapp
  become_user: appuser
  timeout: 10m
  register: migrate_result
  changed_when: "'No migrations to apply' not in result.stdout"

- name: Wait for service
  shell: curl -sf http://localhost:8080/health
  retries: 30
  retry_delay: 2s
  failed_when: "result.rc != 0"

See complete example for detailed deployment workflow.

Real-World Example¶

Dotfiles Manager¶

A complete example showing how to manage and deploy dotfiles using Mooncake.

Features Demonstrated¶

Multi-file organization
Template rendering for dynamic configs
File tree iteration
Conditional deployment by OS
Variable management
Backup functionality
Tag-based workflows

Quick Start¶

cd examples/real-world/dotfiles-manager

# Deploy all dotfiles
mooncake run --config setup.yml

# Deploy only shell configs
mooncake run --config setup.yml --tags shell

# Preview what would be deployed
mooncake run --config setup.yml --dry-run

Directory Structure¶

dotfiles-manager/
├── setup.yml              # Main entry point
├── vars.yml               # User configuration
├── dotfiles/              # Your actual dotfiles
│   ├── shell/
│   │   ├── .bashrc
│   │   └── .zshrc
│   ├── vim/
│   │   └── .vimrc
│   └── git/
│       └── .gitconfig
└── templates/             # Dynamic config templates
    ├── .tmux.conf.j2
    └── .config/
        └── nvim/
            └── init.lua.j2

What It Does¶

Backs up existing dotfiles
Creates necessary directories
Deploys static dotfiles
Renders dynamic configs from templates
Sets appropriate permissions
OS-specific configuration

Configuration¶

Edit vars.yml to customize:

user_email: [email protected]
user_name: Your Name
editor: nvim
shell: zsh
color_scheme: gruvbox

Usage¶

Full Deployment:

mooncake run --config setup.yml

Selective Deployment:

# Only shell configs
mooncake run --config setup.yml --tags shell

# Only vim/neovim
mooncake run --config setup.yml --tags vim

# Only git config
mooncake run --config setup.yml --tags git

Backup Only:

mooncake run --config setup.yml --tags backup

Extending¶

Adding New Dotfiles:

Add file to dotfiles/ directory

Add deployment step in setup.yml:

- name: Deploy new config
  shell: cp {{ item.src }} ~/{{ item.name }}
  with_filetree: ./dotfiles/new-app
  tags:
    - new-app

Adding Templates:

Create template in templates/

Add rendering step:

- name: Render new config
  template:
    src: ./templates/new-config.j2
    dest: ~/.config/new-app/config
  tags:
    - new-app

Real-World Tips¶

Version control - Keep this in git
Test first - Use --dry-run before applying
Incremental - Add configs gradually
Backup - The example includes backup steps
Document - Add comments for custom settings

Summary¶

You've learned all core Mooncake features through these examples:

Feature	Examples
Shell Commands	01, 04, 06, 08, 11
File Operations	03, 06, Real-World
Templates	05, Real-World
Variables	02, 05, 06, 10
Conditionals	04, 08, 09
Loops	06, Real-World
Register	07, 11
Tags	08, Real-World
Sudo	09, 11
Multi-file	10, Real-World
Execution Control	11
Timeouts & Retries	11
Environment Variables	11

Next Steps¶

Read the Guide - Comprehensive documentation
Reference - Detailed config reference
GitHub - View source code
Contributing - Help improve Mooncake