Mac OS X Tiger in a Nutshell

launchd

Mac OS X Tiger introduces the latest and greatest startup scheme, launchd. It has launch-on-demand capabilities and also supports on-demand launching via Mach ports (as does the mach_init.d scheme). launchd also offers the ability to launch on demand based on file system and Unix domain socket events. The property list (.plist) files for system-installed daemons are in /System/Library/LaunchDaemons. Locally-installed daemons can be installed into /Library/LaunchDaemons. Table 11-1 lists and describes the system-installed daemons, most of which have counterparts in Linux and Unix systems.

You can control launch daemons with the launchctl utility. For example, to enable and load a daemon that’s disabled (there will be a Disabled key in its property list file), use launchctl load -w followed by the path to the property list. For example, the following command would be enabled and start the telnet server:

    # launchctl load -w /System/Library/LaunchDaemons/telnet.plist

You can stop and disable this daemon with unload -w:

    # launchctl unload -w /System/Library/LaunchDaemons/telnet.plist

For more information, see launchctl in Chapter 2, or the launchctl manpage.

Table 11-1. Default Mac OS X launch daemons

Property List File	Description	Enabled by default?
bootps.plist	Starts the DHCP/BOOTP daemon.	No
com.apple.atrun.plist	Launches the atrun daemon.	Yes
com.apple.KernelEventAgent.plist	Runs the kernel event agent, which responds to low-level kernel events (such as disk ...