I mounted one of my iPods to load music. It wouldn't work - filesystem is read only. I tested one of the other iPods and it worked okay. Did a Google search, found this page: Fixing iPod on linux read-only errors (mostly). I must have mounted my iPod uncleanly at some point, and I'm not sure if that's from a Mac or from Linux. Once it's been uncleanly unmounted, it will only mount read-only. I'll have to be more careful in future. I attached it to my Mac, ran Disk Utility on it, Repair Disk, and it said everything was fine with it. I dismounted it, mounted it on Linux again and all was well. I could mount it, I could remove a bunch of files and I could add new files.