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Launch Items, Startup Items, and Daemons

Launch items and startup items are special programs that launch other programs or perform one-time operations during startup and login periods. Daemons are programs that run continuously and act as servers for processing client requests. You typically use launch items and startup items to launch daemons or perform periodic maintenance tasks, such as checking the hard drive for corrupted information. Launch items run under the launchd system process and are supported only in Mac OS X v10.4 and later. Startup items are also used to launch system and user-level processes but are deprecated in current versions of Mac OS X. They may be used to launch daemons and run scripts in Mac OS X v10.3.9 and earlier.

Launch items and startup items should not be confused with the login items found in the Accounts system preferences. Login items are typically agent applications that run within a given user’s session and can be configured by that user. Launch items and startup items are not user-configurable.

Few developers should ever need to create launch items or daemons. They are reserved for the special case where you need to guarantee the availability of a particular service. For example, Mac OS X provides a launch item to run the DNS daemon. Similarly, a virus-detection program might install a launch item to launch a daemon that monitors the system for virus-like activity. In both cases, the launch item would run its daemon in the root session, which provides services to all users of the system.

For more information about launch items, startup items, and daemons, see System Startup Programming Topics.

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