Hyper-v disk files, with extensions such as vhdx and vhd can be mounted under linux directly with the libguestfs-tools tool, mind you, many packages will be installed… mostly libraries relating to the formats it is capable of mounting
sudo apt-get install libguestfs-tools
Now, the following command should mount the disk inside the virtual machine
guestmount --add diskname.vhdx --inspector /mount/dir/name
If the system does not detect a system, you will need to tell guestmount what partition to mount, to explore the partitions, you will need ….
virt-filesystems -a disk.vhdx
Once you know your partitions
guestmount --add disk_d.vhdx -m /dev/sda1 /hds/loop
If you would rather mount the disk as read only, you can add the –ro switch
guestmount --add yourVirtualDisk.vhdx --inspector --ro /mnt/anydirectory
To unmount, you will need to use the following command
guestunmount /mnt/anydirectory