Mount a qcow2 disk image

# modprobe nbd max_part=8 
# qemu-nbd --connect=/dev/nbd0 /var/lib/vz/images/100/vm-100-disk-1.qcow2
# fdisk /dev/nbd0 -l 
# mount /dev/nbd0p1 /mnt/somepoint/
# umount /mnt/somepoint/
# qemu-nbd --disconnect /dev/nbd0
# rmmod nbd