How to create focal-server-cloudimg-amd64-vnx.qcow2 image

- Download base image:
wget https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img

  Although the extension is .img it is a qcow2 image:
# file focal-server-cloudimg-amd64.img
focal-server-cloudimg-amd64.img: QEMU QCOW Image (v2), 2361393152 bytes

- Mount the image:
sudo modprobe nbd
sudo qemu-nbd --connect=/dev/nbd0 focal-server-cloudimg-amd64.img
sudo mount /dev/nbd0p1 /mnt

- Allow root login:
sudo sed -i 's/disable_root:.*/disable_root: false/' /mnt//etc/cloud/cloud.cfg

- Allow ssh with user/passwd and root login
sed -i 's/^PasswordAuthentication.*/PasswordAuthentication yes/' /mnt//etc/ssh/sshd_config
sed -i 's/.*PermitRootLogin .*/PermitRootLogin yes/' /mnt//etc/ssh/sshd_config

- Create vnx account and set root password (xxxx password for both)
chroot /mnt
passwd root
adduser vnx
usermod -aG sudo vnx
...

- Exit chroot and unmount the image:
exit
sudo umount /mnt
sudo qemu-nbd --disconnect /dev/nbd0p1

- Rename the image:
mv focal-server-cloudimg-amd64.img focal-server-cloudimg-amd64-vnx.qcow2