v0.1.0

0.1.0 (2026-09-28)

The first release of contemper: build bootable VM images from container
images. You author a VM image as an ordinary container build, push it
like any other image, and contemper turns it into a disk.

This is an early, proof-of-concept release. The path from image to
booting VM works end to end and is tested in CI, but expect rough edges,
missing features and breaking changes before 1.0.

What it does

• contemper convert turns a contemper-ready OCI image into a
  bundle: a UEFI-bootable qcow2 disk (a Unified Kernel Image on the EFI
  partition, a writable ext4 root) plus contemper.json, which records
  the image digests and support images the disk came from. A failed
  conversion leaves no partial bundle behind, and converting again
  replaces the previous bundle as a whole.
• Nothing from the image runs during conversion. contemper merges
  layers and reads files; it needs no container runtime, no root and no
  emulation. An arm64 disk builds on an x86-64 host, and the other way
  round.
• Sources: registry references (using the docker/podman
  credentials you already have), OCI archives, OCI layouts and docker
  archives. Multi-platform images resolve to the target architecture.
• Support images layer what a platform needs on top of your image.
  Their variants let one support image adapt to what it's merged into,
  for example OpenRC vs. systemd.
• Volumes: VOLUME declarations become separate data disks, sized
  by an image label or at deploy time (deploy --volume /data=10GiB),
  and attached per instance. A helper merged into the image formats a
  blank volume on first boot and reuses an existing one, on OpenRC and
  systemd.
• contemper deploy --to local-qemu boots a bundle under QEMU, with
  KVM or HVF acceleration where available and software emulation for a
  foreign architecture.
• Runs on Linux and macOS, amd64 and arm64.

Install

• macOS (Homebrew): brew install contemper-project/tap/contemper
  (also installs e2fsprogs and QEMU).
• Debian/Ubuntu: download the .deb below and
  sudo apt install ./contemper_0.1.0_amd64.deb.
• Fedora/RHEL: download the .rpm below and
  sudo dnf install ./contemper-0.1.0-1.x86_64.rpm.
• Anything else: the .tar.gz archives below, plus the host tools:
  e2fsprogs (mkfs.ext4, debugfs, e2fsck) and qemu-img to convert,
  QEMU and UEFI firmware to deploy.

The packages install what convert needs; for deploy, add the
emulator and firmware for the bundles you boot. See
Install
and Host tools.

Every archive and package is listed in checksums.txt and carries a
signed build provenance attestation:

$ gh attestation verify contemper_0.1.0_linux_amd64.tar.gz --repo contemper-project/contemper

Getting started

• Documentation: https://contemper-project.github.io/contemper/
• An image needs a kernel, a generic initrd and an init system at fixed
  paths, and the io.contemper.ready="true" label. See
  Authoring images;
  examples/ has an Alpine (OpenRC) and a Debian (systemd) image.

Before you rely on it

This release is for trying contemper out, not for production use. CLI
flags and the bundle format will still change (bundles are
formatVersion 1). Known limitations:

• An image where a later layer removes or replaces the target of a
  hardlink is rejected.
• Paths and symlink targets longer than about 1000 bytes are rejected.
• A bundle for a foreign architecture boots under software emulation,
  which is slow.

Please report bugs and ideas in the
issue tracker,
and security issues as described in
SECURITY.md.