Are you trying to mount it manually for some specific reason? If not I would think the program gtkpod-aac is what you're looking for:
manage songs and playlists on an Apple iPod
gtkpod is a platform independent GUI for Apple's iPod using GTK2. It allows
you to upload songs and playlists to your iPod. It supports ID3 tag
editing, multiple charsets for ID3 tags, detects duplicate songs, allows
offline modification of the database with later synchronisation, and more.
This gtkpod version has been build with aac and mp4 support.
If this is what you need then do (in a terminal):
sudo apt-get install gtkpod-aac
NB: I'm assuming from your signature that you're using Ubuntu, since you didn't say....
EDIT: just looked at the title again, you did say ubuntu, apologies...