Currently there is no linux software (or library) that can successfully read, write and update an iOS device's music library running iOS 5 or higher. All applications (that I know of), are dependent on libgpod for this functionality and libgpod has not worked properly with the current versions of iOS for some years now, ever since the database version (DBVersion) of the iTunes library within the device hit version 5.

Your best bet right now is iTunes via wine.