Debian Cloud Image Builder

Builds a minimal Debian stable (Trixie) amd64 qcow2 cloud image using Packer and QEMU, with CI/CD via Forgejo Actions.

What's included

• QEMU guest agent — enabled at boot
• cloud-init — handles SSH keys, user provisioning, network, and disk resize
• Serial console — ttyS0 at 115200 baud for hypervisor access
• Minimal footprint, compressed qcow2 output

CI/CD — Forgejo Actions

Push a tag to trigger a build and publish:

git tag v1.0.0
git push origin v1.0.0

The workflow installs QEMU + Packer, builds the image, and uploads it as a Forgejo release with a SHA256 checksum.

Runner requirements

Requirement	Notes
KVM (/dev/kvm)	Strongly recommended; falls back to software emulation
~6 GB disk	ISO download + build output
Internet access	Fetches Debian ISO and packages

Local build

# Install dependencies
sudo apt-get install -y qemu-system-x86 qemu-utils

# Install Packer (https://developer.hashicorp.com/packer/install)

packer init .
packer build .
# Output: output/debian-cloud-amd64.qcow2

Override variables as needed:

packer build -var disk_size=8G -var cpus=4 .

Variables

Variable	Default	Description
iso_url	Debian stable netinst	URL to the installer ISO
iso_checksum	SHA256SUMS from cdimage.debian.org	Checksum or file: URL
cpus	2	vCPUs for the build VM
memory	2048	RAM in MB
disk_size	4G	Virtual disk size
accelerator	kvm	kvm or tcg (software)

Note: When a new Debian point release ships, update iso_url in variables.pkr.hcl to match the new filename (e.g. debian-13.5.0-amd64-netinst.iso).