Build OCI images for apk-based distributions declaratively!
When maintaining images at scale, the Dockerfile concept built into
Docker is inefficient. If we have a collection of build artifacts,
repositories and a keyring, we can build images directly with APK,
and upload them directly to container registries.
In fact, we can do more than that: using a service like kontain.me, we can serve fresh container images on demand, with the latest package updates, using nothing but declarative configuration.
This part is very much a work in progress, but basically you need
a system with apk (soon: libapk), and this apko tool. You
probably also want the other Chainguard stack components as well,
e.g. crane.
To build an image, use the apko build command:
# apko build config.yaml tag output.tar
This will give you a Docker-style tarball which you can use with
docker load:
# docker load < output.tar
You need root, or at least fakeroot + fakechroot to build images with apko, due to apk-tools' use of chroot(2).
By using the very fast apk package manager to manage build artifacts, we can build images very quickly. This means that developers win with a faster and more easy to reproduce build process.
Some containers are complex, with multiple tightly-coupled services
running in the same container. apko understands this scenario out
of the box, avoiding the need to deal with things like s6-overlay.
If you define a service-bundle entrypoint, it will generate an
appropriate supervision tree and ensure s6 is installed.
As a result of using apk to manage distribution and build artifacts, we will be able to generate SBOMs for containers, using the new apk-tools 3.x SBOM feature.