source: https://thornelabs.net/posts/create-a-bootable-windows-7-or-10-usb-drive-in-linux.html
# fdisk /dev/sdY
create single partition type 7 plus the bootable partition
# mkfs.ntfs -f /dev/sdY1
# ms-sys -7 /dev/sdY
Finally, copy the contents of the mounted Windows 7 ISO to the mounted USB drive
# mount -o loop win7.iso /mnt/iso
# mount /dev/sdY1 /mnt/usb
# cp -r /mnt/iso/* /mnt/usb/