VBoxMount utilizes the virtual disk API of the VirtualBox Porject and the linux kernel's network block device driver to expose a given virtual disk image as a block device. Found partitions on that device can then be mounted with the normal linux mount tools.
You need to have the VirtualBox libraries and headers around. Libraries are shipped with the VirtualBox binary package (and in ubuntu stored in /usr/lib/
Use a kernel > 2.6.26! [Otherwise you'll need to use kpartx which is totally untested].
1) Load the nbd kernel module with max_part option (e.g. max_part=16).
2) Invoke VBoxMount as following: VBoxMount <nbd> <vdi> [vdi...] where <vdi> is your virtual disk image and <nbd> is any of /dev/nbdX where X is most likely something between 0 or 12.
-> After that, you should have /dev/nbdXpY where Y is now mapped to the partitions.
3) You can mount those with the normal mount tools, e.g.: "mount /dev/nbd0p0 /mnt".
"VBoxMount -u /dev/nbdX"