When packaging it is worth note that Apple reserves some positional paremeters for your scripts. These are defined at http://developer.apple.com/mac/library/documentation/DeveloperTools/Conceptual/SoftwareDistribution/Install_Operations/Install_Operations.html#//apple_ref/doc/uid/10000145i-CH14-SW1 They include: $1: Path to the package $2: Path to the destination. $3: Installation volume. $4: Root directory