sudo fdisk -lu part.ext4 | awk '$1 == "part.ext4" { print $3 }' # Start
# offset = $Start * ${SectorSize:-512}
sudo losetup -o $offset /dev/loop0 part.ext4
sudo fsck -fv /dev/loop0
sudo mount /dev/loop0 /mnt
sudo umount /mnt
sudo losetup -d /dev/loop0