This will depend on if it is an OLDER IPOD or a NEWER IPOD.
using gtkpod
using Rhythmbox
Rhythmbox is also supposed to work with the iPod
Launch Rhythmbox. Find it in Applications > Sound and Video > Rhythmbox Music Player. Step Two
Connect your iPhone via USB. It will appear under Devices.
Click Music in your computer’s library. Browse for songs to add to your iPhone. Sync them to your iPhone by Dragging and Dropping onto your iPhone’s icon under devices.