You can create an installer plug-in, which is a Cocoa downloadable package that can contain your own user interface and code. When you add the plug-in to the Installer package, the Installer application displays your plug-in interface as an additional step in the installation process.
Apple code sample and available documentation here . There is a great explanation of the process here .
Unfortunately, inserting a plug-in package into your installer package has become unnecessarily complicated, as in PackageMaker 3.0 and in its flat format.
Once you have created your plug-in, you must first create your installer package as usual. After creating it, you need to go to the Edit menu in PackageMaker and open the Flat Packet Editor . Open the installer package and insert the plug-in in the appropriate place, as in Finder, with the installer package 2.0. That is, you need to create the Plugins folder and inside it you need to insert your package and the InstallerSections.plist file (which is shown in the example above).
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