I'm planning on shrinking my root ext3 partition to make room for a new one. This thread mentioned resize2fs and parted. I was wondering if I could use these tools to resize / while it's still mounted. If not, how do I go about doing it offline?
I think that if you use qtparted, it tells you to unmount first. Dunno about anything else.
You'll have to unmount. The easiest way is to boot up with a Live CD that includes the required tools - that way your partition is unmounted, and you can do waht you like with it.