I think the only requirement is that the iPod have the Apple firmware on it
(if it boots ans shows the menu screen) and that it be formated in FAT32 and not the
Apple HPFS. If your Linux system shows that it is mounted with a FAT32 file system
and you can see the directory structure you are good to go.
I thought that the iPods were normally shipped with the HPFS file system and that you had to reformat them when using with Windows, but since most of them are used with PC's these days (in the VERY early iPod days they were only sold with Mac's) maybe Apple is now shipping them with FAT32 except when sold at an Apple computer store.