launchdmacOS

launchd macOS is the system and service management framework used by macOS to uniformly start, stop, and manage daemons, agents, and scripts. Designed to replace traditional init and cron mechanisms, launchd coordinates the lifecycle of services from boot time and can also launch them on demand or in response to events.

At the core, launchd is the central manager for launch services, typically started by the kernel as the first userland process. It uses job definitions written as XML property list files (.plist) to describe how and when a program should run. Jobs can be configured to run at load, on a timer, when a socket becomes available, or on other conditions. KeepAlive settings allow services to be restarted automatically if they terminate.

Plist files for launchd are stored in system-wide and user-specific locations, such as /System/Library/LaunchDaemons, /System/Library/LaunchAgents, /Library/LaunchDaemons, /Library/LaunchAgents, and ~/Library/LaunchAgents. Modern macOS versions with System Integrity Protection restrict modifications to some system paths, affecting how certain plists are managed.

Management of launchd is performed with the launchctl command, which can load and unload jobs, inspect status, and modify runtime behavior. Administrators use LaunchDaemons for system services and LaunchAgents for user-specific tasks, with a combination that provides both persistent background services and on-demand execution.

In summary, launchd on macOS provides a unified, extensible approach to service management, enabling reliable startup, lifecycle control, and on-demand activation of background processes through standardized plist configurations.