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Chapter 4 Restarting or Shutting Down a Computer 55
Monitoring and Restarting Critical Services
In earloier versions of Mac OS X, a daemon called watchdog monitored critical services
and restarted them if they failed or quit unexpectedly after a computer restarted.
The watchdog daemon relied on the configuration file watchdog.conf, located in /etc.
In Mac OS X Server version 10.4, watchdog has been replaced by launchd. The launchd
daemon manages other daemons, both for the computer as a whole and for individual
users. You can configure the launchd daemon to launch other daemons on demand,
based on criteria specified in their respective XML property lists.
During system startup, launchd is the first process invoked by the kernel to run and set
up the rest of the computer. In Mac OS X Server, it is preferable to have your daemon
started by
launchd.
Note: Some system administrators need to modify the boot process to insert a script or
implement a change in the default system configuration. System administrators are
encouraged to work with launchd to implement whatever changes they require, and
avoid modifying rc or creating a SystemStarter Startup Item. The rc command script
may be phased out in the future.
The configuration files are located in the following folders:
Folder Usage
/System/Library/LaunchAgents Configuration for the system
/System/Library/LaunchDaemons Configuration for the daemons
~/Library/LaunchAgents Configuration per user