packer-devbox

Packer template that builds a base Ubuntu 24.04 developer VM as a qcow2 image.

What's included

Tool	Details
Docker Engine	CE, CLI, Buildx, Compose plugin
QEMU/KVM + libvirt	For running nested VMs
GitHub CLI	gh via official apt repo
Rust	Stable toolchain via rustup
Python tools	uv, ruff, ty via Astral installers
Claude Code	CLI via official installer
Build dependencies	build-essential, pkg-config, libssl-dev, libvirt-dev, etc.

The default user is sherpa. It is pre-added to the docker, libvirt, and kvm groups. Cloud-init runs on first boot so SSH keys, passwords, and any further configuration are set by the user.

Prerequisites

• QEMU/KVM (qemu-system-x86_64, /dev/kvm)
• Packer ≥ 1.10
• ssh-keygen

Build

Clone the repo with submodules:

git clone --recurse-submodules https://github.com/bwks/packer-devbox.git
cd packer-devbox

Install the QEMU plugin (one-time):

packer init devbox.pkr.hcl

Generate a temporary build keypair and run Packer:

ssh-keygen -t ed25519 -f /tmp/packer_key -N "" -C "packer-build"

packer build \
  -var "ssh_public_key=$(cat /tmp/packer_key.pub)" \
  -var "ssh_private_key_file=/tmp/packer_key" \
  devbox.pkr.hcl

The Ubuntu 24.04 cloud image is downloaded and cached in packer_cache/ on first run.

Output: output/devbox.qcow2 (~20 GB sparse qcow2)

Using the image

Boot with your own cloud-init user-data to configure the sherpa user:

#cloud-config
users:
  - name: sherpa
    ssh_authorized_keys:
      - ssh-ed25519 AAAA...yourkey
    sudo: ALL=(ALL) NOPASSWD:ALL
    shell: /bin/bash

Pass it as a seed ISO:

cloud-localds seed.iso user-data
qemu-system-x86_64 \
  -enable-kvm -m 4096 -smp 4 \
  -drive file=output/devbox.qcow2,if=virtio \
  -drive file=seed.iso,if=virtio,format=raw,readonly=on \
  -netdev user,id=net0,hostfwd=tcp::2222-:22 \
  -device virtio-net-pci,netdev=net0

Then SSH in:

ssh -p 2222 sherpa@localhost

Updating installer scripts

The installer scripts are a git submodule. To pull the latest:

git submodule update --remote installer-scripts
git add installer-scripts
git commit -m "bump installer-scripts"