On Linux I used to resize MBR partitions using fdisk, even on live filesystems, and then issue a resize2fs/pvresize/... (depending on fs type) to get the new space allocated. Lately I've been using Xen and GPT partitions, and I've noticed that unfortunately parted doesn't seem to allow on-the-fly resizing of a mounted partition, in fact it will complain: Error: Partition XXX is being used. You must unmount it before you modify it with Parted. I've tried both the resize command and even rm + mkpart combination, but they will both complain about the partition being mounted. How can I do that?