Ubuntu:
Add to /etc/initramfs-tools/modules
hv_utils
hv_vmbus
hv_storvsc
hv_blkvsc
hv_netvsc
Install
apt install linux-virtual linux-cloud-tools-virtual linux-tools-virtual
Update initramfs:
update-initramfs -u
Reboot. Done.
Debian:
apt install hyperv-daemons