do ntfsresize and gparted work on a disk image mounted through the loop device?

Question

I need to resize a NTFS partition in a disk for which I have an image (dumped with dd).

I mounted it through the loop device on linux:

# losetup -o 32256 /dev/loop0 disk.img # I got the offset from looking at fdisk's output
# mount /tmp/t /dev/loop0
# ls /tmp/t
[content of NTFS partition shows correctly]
# umount /tmp/t
# gparted /dev/loop0

gparted shows me the disk correctly; it just contains one large NTFS partition I want to shrink.

I have it had it running for one hour now.

Question: will this work? There is lots of disk access but the timestamp and size of the underlying file disk.img remain unchanged.

Answer 1

Yes, loop devices are indistinguishable from 'normal' block devices for higher layer applications (like gparted). Loop device access doesn't change timestamp of mounted file: it is a bug.

Also, while kernel won't create partition subdevices, you can make them with kpartx if you need so (just in case).