so i should have run this?
ro
rom
fsck.ext2 -fay -b 32768 /dev/hda4
also i did run "umount /dev/hdc4 "..i just forgot to copy it here!
OK. I skimmed over it and said what I would have done. Tony's FAQ (and Boelle) were correct.
What you're doing is this:
"ro" - remount the root filesystem as read-only. This is needed because Linux requires a reboot if you check a partition that's mounted read-write. Just in case something changed. The root filesystem is where all of the good stuff on a Unix-like box is usually kept. Think of it as C:\ combined with C:\Windows\System32 on a Windows box.
"umount /dev/hda4" - unmount the music partition of the first disk. Not really needed, but safe enough.
"swapon /swapfile" - checking the disk needs quite a lot of memory, so enabling swap is a good idea.
various "fsck" commands - these check the root partition and the two music partitions.
"swapoff /swapfile" - we don't need the swap any more. Keeping it enabled requires the disk to stay spun up, and we usually try to avoid that. It's probably not a big deal, since you'll be powering down before moving the empeg back to your car.
"sync" - ensure everything's flushed to the disk.
So, yes, Boelle was correct: unmounting the second music partition cleanly ("umount /dev/hdc4") should have prevented the warning, but it's not strictly necessary.
To be honest, you can usually ignore the warning until you've finished the copy, at which point you should definitely run the listed commands.