debian/ubuntu kvm virsh install with cloud init

This repo describes how to auto install Debian 12, Debian 13, Ubuntu 22.04 and Ubuntu 24.04 with virsh-install and cloud-init. Which images you can use, and which images you should not use. How to add user passwords with hashes and how to create harddisk images from templates.

screen recordings of tool

sources for images

• https://cdimage.debian.org/cdimage/cloud/
• https://cloud-images.ubuntu.com/noble/current/

get images

Do not use genericcloud images, they do not contain sata ahci drivers for cloud init.

cd /isos

# Debian
wget https://cdimage.debian.org/cdimage/cloud/bookworm/latest/debian-12-generic-amd64.qcow2
wget https://cdimage.debian.org/cdimage/cloud/trixie/latest/debian-13-generic-amd64.qcow2

# Ubuntu
wget https://cloud-images.ubuntu.com/releases/24.04/release/ubuntu-24.04-server-cloudimg-amd64.img
wget https://cloud-images.ubuntu.com/releases/22.04/release/ubuntu-22.04-server-cloudimg-amd64.img

The generator can also download missing base images automatically on first run.

prepare cloud init file

This python script manages the full VM lifecycle:

• First run: asks for distro, architecture, VM name, username, password, SSH key and network type
• Saves parameters to a .session file for subsequent runs
• Subsequent runs: detects existing VM, offers to show IP or recreate it
• Automatically generates cloud-init.yml, meta-data.yml and copies them to /isos
• For Ubuntu: additionally creates a seed ISO (genisoimage) and a network-config.yml
• Creates the overlay disk image and runs virt-install

It needs mkpasswd (packaged with whois) and genisoimage to work.

sudo apt-get install whois genisoimage

python3 generator.py
# or
uv run generator.py

supported distributions and architectures

Distro	Version	amd64	arm64
Debian	12	✔	✔
Debian	13	✔	✔
Ubuntu	22.04	✔	✔
Ubuntu	24.04	✔	✔

templates

The templates/ directory contains files that are merged into the generated cloud-init.yml:

• cloud-init-template.yml – base template (users and runcmd are overwritten by the generator)
• package-config.txt – list of runcmd lines to execute (one per line)
• system-config.txt – shell script injected as a runcmd block
• amd64-tools.sh – additional tooling script (downloaded automatically if missing)

create cloud init without tool

mkpasswd -m sha-512 # to generate hash for your user password
cp cloud-init.yml /isos/cloud-init.yml

check supported os variant list

virt-install --os-variant list

virsh net-start default # check if default network is running

Create base hard disk image and install debian13 with cloud init

# create overlay disk image
qemu-img create -f qcow2 -F qcow2 -o backing_file=/isos/debian-13-generic-amd64.qcow2 /isos/debian13.qcow2 30G

virt-install \
  --name debian13 \
  --arch x86_64 \
  --machine q35 \
  --cpu host-passthrough \
  --memory 4096 \
  --vcpus 2 \
  --disk /isos/debian13.qcow2,device=disk,bus=virtio \
  --os-variant debian13 \
  --virt-type kvm \
  --graphics none \
  --console pty,target_type=serial \
  --network network=default,model=virtio \
  --cloud-init user-data=/isos/cloud-init.yml,meta-data=/isos/meta-data.yml \
  --boot uefi \
  --noautoconsole \
  --import

Create base hard disk image and install Ubuntu 24.04 with cloud init

Ubuntu requires a seed ISO instead of --cloud-init due to EFI + IDE CDROM incompatibility.

# create overlay disk image
qemu-img create -f qcow2 -F qcow2 -o backing_file=/isos/ubuntu-24.04-server-cloudimg-amd64.img /isos/ubuntu2404.qcow2 30G

# create seed ISO (user-data = cloud-init.yml, meta-data = meta-data.yml, network-config = network-config.yml)
genisoimage -output /isos/ubuntu2404-seed.iso -volid cidata -joliet -rock \
  /isos/cloud-init.yml /isos/meta-data.yml /isos/network-config.yml

virt-install \
  --name ubuntu2404 \
  --arch x86_64 \
  --machine q35 \
  --cpu host-passthrough \
  --memory 4096 \
  --vcpus 2 \
  --disk /isos/ubuntu2404.qcow2,device=disk,bus=virtio \
  --disk /isos/ubuntu2404-seed.iso,device=cdrom,bus=scsi \
  --os-variant ubuntu24.04 \
  --virt-type kvm \
  --graphics none \
  --console pty,target_type=serial \
  --network network=default,model=virtio \
  --boot uefi \
  --noautoconsole \
  --import

delete vms

virsh destroy debian13
virsh undefine debian13 --remove-all-storage --nvram

virsh destroy ubuntu2404
virsh undefine ubuntu2404 --remove-all-storage --nvram

cloud init tools

check cloud-init status

sudo journalctl -u cloud-init
sudo cat /var/log/cloud-init.log

trigger cloud init

sudo cloud-init clean
sudo cloud-init init
sudo cloud-init modules --mode=config
sudo cloud-init modules --mode=final