Reverting individual system components

You force the installation of older versions of specific components with the aid of Pacifist. This can be useful in situations where a newer component causes problems that can be alleviated by reverting to the older version. For instance, if a new version of the AirPort kernel extension (/System/Library/Extensions/AppleAirport.kext) breaks wireless connectivity, you can force installation of an older version of this kernel extension via these steps:

1. Download the appropriate combo updater from Apple's download page.
2. Download and install the shareware application Pacifist
3. Drag the Mac OS X combo installer package (e.g. MacOSXUpd10.4.9Intel.pkg) onto the Pacifist application icon.
4. Scan the list of installed files for items that might be causing your problem by clicking on the disclosure triangles. As mentioned above, /System/Library/Extensions/AppleAirport.kext might be implicated in an AirPort issue, for instance. Pay particular attention to >/System/Library/CoreServices, /System/Library/Extensions(files stored here are kernel extensions -- items that are used to interact through an abstraction layer with the Mac OS X kernel, and can be implicated in kernel panics and other issues) and /System/Library/Frameworks
5. Find the file you are looking for by clicking the disclosure triangles to reveal the targeted location.
6. Select the file in question and click the Install button in Pacifist. You will be required to enter your administrator password.
7. Restart your Mac

You should generally not mix and match components from different system versions because of potential compatibility issues. You will also lose any refinements brought about by the revision. Still, in a bind, replacing newer items with older ones can solve otherwise insoluble issues.

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