Created without the 64bit feature with:
truncate -s 1M mount_ext4.imgmkfs.ext4 mount_ext4.img -O ^64bitsudo mkdir /mnt/tmpsudo mount -oloop mount_ext4.img /mnt/tmpsudo cp hello_world.txt /mnt/tmp/sudo umount /mnt/tmpe2fsck -f mount_ext4.imgresize2fs -M mount_ext4.img (counting number of reported blocks)truncate -o --size NN mount_ext4.img (where NN=number of blocks above)