Procedure show in this page was tested on the ipod-nano, but It will work with any other "dockable" ipod hardware.
When you plug the USB cable to a linux box to power up your ipod you will get the message "Do Not Disconnect" in your Ipod screen. This message is similar to that shown when you synchronise files with a Windows or MacOS machine. When this message is displayed your ipod does not respond to any key and it is not capable of playing music.
The USB port has four different pins. Two for power (both extremes) and the other two for data transmitting (two central ones). When you plug your ipod to the linux box, the ipod detects a connection on the two data pins, trying to send information for synchronisation. It is possible to solve this problem just by covering the two central pins of the apple USB cable with a small piece of plastic or hard paper, as follows:
Cut a small stripe of plastic of hard paper. Bend it as shown in the picture...
Insert the strip centred into the apple USB plug to cover internally the data pins (two central ones).
Plug the USB into your linux box taking care that the paper/plastic stripe does not moves duringh the insertion...
After doing this, and connecting the cable to the USB to your ipod you are able to...
recarge its battery and...
...reproduce your music.
Enjoy your ipod ;-)