🧾 Summary

This document provides a comprehensive guide to macOS launchd, the unified service management framework that replaces traditional Unix init systems, cron, and inetd. Understanding launchd is essential for managing services and automating tasks on macOS.

🎯 Key Concepts

Launchd serves as the single point of truth for all service management on macOS, handling: - System daemons (LaunchDaemons) - User agents (LaunchAgents) - Scheduled jobs (cron replacement) - On-demand services (inetd replacement) - Event-triggered tasks

🔧 Core Components

Property List (plist) Files

Services are defined using XML property lists with standardized keys: - Label: Unique service identifier - ProgramArguments: Command and arguments to execute - RunAtLoad: Start service at load time - KeepAlive: Restart if service exits

Service Types

Agents: Run in user context (~/Library/LaunchAgents/)
Daemons: Run in system context (/Library/LaunchDaemons/, /System/Library/LaunchDaemons/)

📋 Essential Commands

# Service management
launchctl load/unload plist-file     # Load/unload service
launchctl start/stop service-name    # Start/stop service
launchctl list                      # List services

# Modern commands (macOS 10.10+)
launchctl bootstrap/bootout domain path  # Bootstrap/destroy
launchctl enable/disable service    # Enable/disable

🛠️ Common Use Cases

Scheduled Tasks: Replace cron with StartCalendarInterval
File Monitoring: Use WatchPaths for filesystem events
Network Services: Define sockets for on-demand services
Resource Management: Set limits with SoftResourceLimits

🔍 Troubleshooting Tips

Validate plist syntax with plutil -lint
Check service logs in ~/Library/Logs/
Monitor launchd activity with log stream
Use launchctl print for detailed service information