Ok, I understand.
What I did was quite simple, here a short summary:
- Extract the initrd.img to a temporary directory
- Edit the file init so that a shell is called before the boot process continues (almost at the end of the file).
- Copy the missing kernel module hv_vmbus.ko to the modules directory.
- Create a new newinitrd.img
- Boot with the new created newinitrd.img: While seeing the grub-menu press ‘e’ to edit the menu-entry and change the filename. Boot with pressing F10.
- The initrd will start a shell. Now you can load the kernel module hv_vmbus.ko manually and all the magic happens.
- Continue booting through exiting the shell (Strg+D)