Mac OS X Leopard - ARCAism

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CHAPTER 2 THE FILE SYSTEM
Figure 2-1. A simple view of Leopard’s default file system
The Library Folders
One thing you may notice about the file system is that there are multiple Library folders. This is
by design, and while there are many similarities between the contents of the Library folders, they
are scoped differently.
NOTE There are actually four Library domains, although generally you’ll only see three
Library folders. Some applications can contain their own Library folders that contain plug-ins
or other information that is used only when that application is running.
The Library folders each contain the necessary support items for the applications on your
system, as well as the system itself. These include things like preference settings, cache items,
scripts, and screen savers. In practice, you almost never need to fuss with the contents of any
Library folder; however, there are times when it may benefit you to do so (especially the Library
folder in your home directory). That said, for each Library folder there are certain rules. We’ll
look at each of the three primary Library folders in general first, and then we’ll explore common
subitems contained in Library folders in general.
The Library and System Library Folders
The primary Library folder (/Library) and the Library folder contained in the System folder
(/System/Library) have global scope. That is, their contents support every aspect of the system.
Specifically, the System Library folder contains the items necessary for the system to operate, and
the primary Library folder contains the items necessary for most applications, third-party hardware,
and other items that affect every user on the system.
As a general rule, the System Library is sacred. Only Apple should install items in it, and
only Apple should alter any of those items. As such, there is almost no reason for you (or me) to
touch anything in there unless you are 100 percent sure you know exactly what you are doing
and that doing it here is the only way to solve your problem. Changing anything here can cause
very bad things to happen (or even worse . . . nothing at all).