My daughter got an Apple iPod nano 5G (with camera) for her birthday. Naturally she wanted to put some music on it right away. We could see the iPod as a USB storage device, even transfer data and music. However, the iPod did not recognize the music and therefore could not play it.
To quickly get the iPod nano 5G to work with Ubuntu 10.04 you can either initalize it on a Windows or Apple PC using iTunes. You only need to copy one piece of music onto the iPod.
After this, the iPods local database for music is initialized.
Use Rhythmbox or gtkpod to transfer music to and from the iPod.
If you don't have a Mac or PC available, go to the store and ask the clerk to initialize the iPod for you (Tell them you don't need iTunes only afterwards ;-))
iPod uses a local SqLite database to store meta information about music. It gets updated when synced by iTunes. Music is stored in a subfolder /iPod_Control/Music/fxx where xx is a number starting from 00. Rhythmbox stores music correctly in the directory but does not get the last part correct (fxx). Only when the iTunedDB is initialized can Rhythmbox store music in any of the prepared directory. The iPod finds the music and is able to play it.