registry.k8s.io VS go-containerregistry

If you stop to think about, what AWS is selling here, it's quite funny. Most of the infrastructure behind registry.k8s.io is hosted on AWS (and also GCP). So AWS essentially tells you: Don't trust the upstream registry, it might go down, cache it on your own registry, hosted also by us.

For example: if you only allow cluster autoscaler and metrics server from registry.k8s.io you can pull those images through the cache as someone who has create repo IAM privileges. If someone without create repo privileges tries to pull a new image it will fail because they can't create the initial repo.

https://registry.k8s.io (the root url at /) redirects you to https://github.com/kubernetes/registry.k8s.io where we have an issue tracker.

❗ This container is having trouble accessing https://registry.k8s.io

Hosting a forwarding / redirect server instead of actually hosting images is probably a decent idea.

The K8s proxy is redirecting from only hosting on GCR to community-owned registries - https://kubernetes.io/blog/2023/03/10/image-registry-redirec...

You can view the code here - https://github.com/kubernetes/registry.k8s.io

But because everyone is already pointing at gcr.io (just like many openfaas users point at docker.io/) - they're having to do a huge campaign to announce the new URL - the same would apply with the author's solution here.

I wrote some automation for hosting (not redirects) in arkade with the OSS registry - Get a TLS-enabled Docker registry in 5 minutes - https://blog.alexellis.io/get-a-tls-enabled-docker-registry-...

The registry is also something you can run on a VM if you so wish, and have act as a pull through cache.

Apart from reliability - GitHub's container registry is the current next best option - but we have to ask ourselves, what happens when they start charging or the outages start to last longer or are more frequent than 1-2 times per week as we've seen in Q1 2023.

One annoyance with how docker images are specified is they include the location where they are stored. So if you want to change where you store you image you break everyone.

I wonder if what regsitry.k8s.io does could be generalized:

https://github.com/kubernetes/registry.k8s.io/blob/main/cmd/...

The idea is the depending on which cloud you are pulling the image from, they will use the closest blob store to service the request. This also has the effect that you could change the source of truth for the registry without breaking all Dockerfiles.

If you are using updated helm charts then most of them have already replaced with registry.k8s.io, for example nginx ingress so not really breaking change.

I also explored another module, go-containerregistry, in order to build images without root privileges. The approach is completely different, and we can manipulate each component of the container image separately. This can present an advantage, if you're looking for a way to fine tune things.

Use crane ls in a different job to check the tags in the registry. Create an artifact from its output that you evaluate in your kaniko job to check if the build should run or not.

Multi-arch builds are easy to "transfer" IMHO

crane cp docker.io/openfaas/gateway:0.10.0 ghcr.io/openfaas/gateway:0.10.0

If you've not used it yet - do take a look. Crane doesn't pull the images into a local Docker library for re-tagging and re-pushing.

https://github.com/google/go-containerregistry/blob/main/cmd...

crane - tool to copy images from one repo to another - https://github.com/google/go-containerregistry/blob/main/cmd/crane/doc/crane.md

pretty sure the crane being referred by alex is this one: https://github.com/google/go-containerregistry/tree/main/cmd/crane

https://github.com/google/go-containerregistry/tree/main/cmd...

It was recommended in this article:

This is one of my absolute favorite topics. Pardon me while I rant and self-promote :D

Dockerfiles are great for flexibility, and have been a critical contributor to the adoption of Docker containers. It's very easy to take a base image, add a thing to it, and publish your version.

Unfortunately Dockerfiles are also full of gotchas and opaque cargo-culted best practices to avoid them. Being an open-ended execution environment, it's basically impossible to tell even during the build what's being added to the image, which has downstream implications for anybody trying to get an SBOM from the image for example.

Instead, I contribute to a number of tools to build and manage images without Dockerfiles. Each of them are less featureful than Dockerfiles, but being more constrained in what they can do, you can get a lot more visibility into what they're doing, since they're not able to do "whatever the user wants".

1. https://github.com/google/go-containerregistry is a Go module to interact with images in the registry and in tarballs and layouts, in the local docker daemon. You can append layers, squash layers, modify metadata, etc.

2. crane is a CLI that uses the above (in the same repo) to make many of the same modifications from the commandline. `crane append` for instance adds a layer containing some contents to an image, entirely in the registry, without even pulling the base image.

3. ko (https://ko.build) is a tool to build Go applications into images without Dockerfiles or Docker at all. It runs `go build`, appends that binary on top of a base image, and pushes it directly to the registry. It generates an SBOM declaring what Go modules went into the app it put into the image, since that's all it can do.

4. apko (https://apko.dev) is a tool to assemble an image from pre-built apks, without Docker. It's capable of producing "distroless" images easily with config in YAML. It generates an SBOM declaring exactly what apks it put in the image, since that's all it can do.

Bazel's rules_docker is another contender in the space, and GCP's distroless images use it to place Debian .debs into an image. Apko is its spiritual successor, and uses YAML instead of Bazel's own config language, which makes it a lot easier to adopt and use (IMO), with all of the same benefits.

I'm excited to see more folks realizing that Dockerfiles aren't always necessary, and can sometimes make your life harder. I'm extra excited to see more tools and tutorials digging into the details of how container images work, and preaching the gospel that they can be built and modified using existing tooling and relatively simple libraries. Excellent article!

Look at using tools like skopeo or crane

Pretty much any tool works: docker, podman, kaniko, crane(if you're brave), ko... list goes on.