#install tools qemu-kvm (debian based distros)
$ sudo apt-get install qemu-kvm

#load module
$ sudo modprobe nbd

#create loopback dev for the image
$ sudo qemu-nbd -c /dev/nbd0 <path to virtual disk>.vdi

#mount the partitions, that are exposed as /dev/nbd0pXXX
$ sudo mount  -o noatime,noexec /dev/nbd0p1 /tmp/vdi/

#in the end unmount && shutdown the ndb
$ sudo umount /tmp/vdi/
$ sudo qemu-nbd -d /dev/nbd0