Back when I was using OS 2, I would use a script that I modified from to swap between two music/video libraries, designated ~/Media/iTunes_Control and ~/Media/iTunes_Control_2. The script would swap the two folders so that after swapping, and my iPod application would use the relevant media file in the relevant folder:

if [ -e /var/mobile/Media/iTunes_Control_2 ]
	mv /var/mobile/Media/iTunes_Control /var/mobile/Media/iTunes_Control_temp
	mv /var/mobile/Media/iTunes_Control_2 /var/mobile/Media/iTunes_Control
	mv /var/mobile/Media/iTunes_Control_temp /var/mobile/Media/iTunes_Control_2
	mv /var/mobile/Media/iTunes_Control /var/mobile/Media/iTunes_Control_2
	mkdir /var/mobile/Media/iTunes_Control
Interestingly enough, it seems that with OS 3, this no longer works. The script does swap the folders as expected, but the iPod does not "realize" that the library has changed. That is, it still contains a listing of all the media under the previous library, but of course, when you try to play that media, it no longer works because it has now moved to iTunes_Control_2.

It seems that whereas with OS 2, both the names and the actual content of the media library were present under ~/Media/iTunes_Control, whereas under OS 3, only the content is under this folder (and the names of the media are in another folder). I was wondering if anyone knew what was going on, and in particular, where the name of the media are stored?