sudo qemu-nbd -c /dev/nbd0  macos.vdi
sudo kpartx -a /dev/nbd0
sudo mount /dev/mapper/nbd0p2 /home/sierra/
sudo cp ~/Downloads/Xcode_8.2.1.xip /home/sierra/home/
cp: cannot create regular file '/home/sierra/home/Xcode_8.2.1.xip': Read-only file system