mount a VirtualBox VDI file

These are the steps that worked for me, all steps as root:

• install qemu-kvm if not present:
  yum install qemu-kvm
• modprobe nbd max_part=16
  (the max_part was required)
• qemu-nbd -c /dev/nbd0 <your vdi filename>
• partprobe /dev/nbd0
  (yum install parted if you don't have partprobe)
• ls -l /dev/nbd0p* to see the partition names
• mount /dev/nbd0p1 /e
  (earlier I created mount point /e)