In addition to the colourfull apps and widgets that we see on a daily basis, there are a number of hidden UNIX programs that provide essential background services. These are called Daemons in the UNIX world - Windows users will be more familiar with the term Services.
Daemons tend not to produce any graphical output, nor do they allow the user to directly interact with them. OS X comes with a number of traditional UNIX daemons pre-installed - this is a very incomplete list:
- Apache,
- AppleShare,
- Cron,
- LDAP,
- SSH,
Services are started up by a Darwin daemon called SystemStarter. SystemStarter looks at the configuration files and plists in /System/Library/StartupItems. A StartupItem is a collection of resource files that describe what the purpose of a deamon is and let the SystemStarter know what order they should be started.
- SystemStarter - Starts daemons.
- StartupItems - Tell the SystemStarter how to start the daemons.