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The Libraries of Mac OS X: /Library

As I explained earlier in this chapter, this folder stores files that are available to all local users and that can be modified by an administrative user. Inside this folder, you will find the following folders.

Figure 4.10Figure 4.10 The /Library folder.

Application Support

This folder contains accessory software for various applications, such as the StuffIt Engine.cfm file, used by StuffIt compression software.


The profiles you create via the ColorSync System Preferences window are stored here.

Contextual Menu Items

Third-party software that adds items to Mac OS X's contextual-menu feature (accessed when you Control-click an item) is stored here.

Desktop Pictures

The background pictures that you can select via the Desktop System Preferences window are stored here.


Some programs that provide Read Me files and other documentation, accessed via commands within the application (such as Help), store their documentation files here.


This folder is similar in function to the Fonts folder in /System/Library, except that these fonts are not considered to be essential. As an administrator, you can add fonts to or remove fonts from this folder.


"Take Note: Multiple Folders of the Same Name in Multiple Library Folders," earlier in this chapter.

Internet Plug-Ins

Plug-ins used with your browser, such as the QuickTime and Shockwave plug-ins, are stored here.

Modem Scripts

This folder is the location of the modem scripts that you can choose from the Modem pop-up menu. You specify these scripts in the Modem tab for the Internal Modem protocol in the Network System Preferences window. (Whew—that was a mouthful of terminology!)


"Take Note: Modem Scripts," in Chapter 8, for related information.


A few systemwide preferences (.plist) files are stored here, such as those for loginwindow. In general, you will have little reason to modify preferences files in this folder.


  • "Take Note: Preferences Files in Mac OS X," in Chapter 3, for more information on .plist files.

  • Chapter 5 for more information on loginwindow.


This folder is where you will find support software for printers, in addition to the LaserWriter support files located in System/Library/Printers. In particular, drivers for Epson, Hewlett-Packard, and Lexmark printers are stored here.


Chapter 7 for more information on printing, including details on PPD and PDE files.


Every time you install a Mac OS X update, a receipt .pkg file for the update is stored in this folder. In certain situations, as discussed in Chapter 2, the OS (especially Software Update) uses these files as a means of knowing that a given update has been installed.


This folder is the equivalent of the StartupItems folder in /System/Library. The main difference is that this folder is used for third-party software, as opposed to the preinstalled Mac OS X items stored in the /System/Library folder. If you install Timbuktu Pro, it will install a Startup Item in this folder. This item is needed for the Timbuktu software to be active at startup, no matter which user logs in. The actual Timbuktu application is located elsewhere, most likely in your Applications folder. Similarly, the Retrospect backup software also installs an folder, called RetroRunHelper, in the Startup Items folder.

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