skopeo VS distribution-spec

I believe skopeo should allow you to: https://github.com/containers/skopeo

I decided to go searching for an alternative means to pull a docker image. In my search I discovered Skopeo, an alternative method to download Docker images that proved to be surprisingly effective. It not only downloaded the image faster, it also allowed me to save my image in a tar file, which means you can pull an image on one system and share that image to another system, loading it easily to docker instance on that system. This can be very beneficial if you have multiple systems and don't want to download an image multiple times.

But I'd suggest looking into if it's solved by other tools already, like regclient/regclient and their regsync features or something like containers/skopeo.

Have a use case where we have a CLI (built with cobra) for our dev teams which can execute common tasks. One of those tasks we want to implement is to copy docker images from the internet to our internal registry. A tool such as skopeo can do this and much more. Instead of essentially re-writing the functionality directly into our CLI we'd like to embed it. This would also negate the need for the dev teams to manage multiple CLI tools.

Self hoisting here, I put this together to make it easier to generate single (extra) layer docker images without needing a docker agent, capabilities, chroot, etc: https://github.com/andrewbaxter/dinker

Caveat: it doesn't work on Fly.io. They seem to be having some issue with OCI manifests: https://github.com/containers/skopeo/issues/1881 . They're also having issues with new docker versions pushing from CI: https://community.fly.io/t/deploying-to-fly-via-github-actio... ... the timing of this post seems weird.

FWIW the article says

> create a Docker image, also known as an OCI image

I don't think this is quite right. From my investigation, Docker and OCI images are basically content addressed trees, starting with a root manifest that points to other files and their hashes (root -> images -> layers -> layer configs + files). The OCI manifests and configs are separate to Docker manifests and configs and basically Docker will support both side by side.

skopeo is another tool worth looking into. we've started deploying amd and arm nodes into our k8s clusters, and this tool was incredibly easy to build around for getting multi-arch images into our container registry.

I would use skopeo, the tool is quite handy for working with remote images. https://github.com/containers/skopeo

Using distroless images not only reduces the size of the container image it also reduces the surface attack. The need for container image signing is because even with the distroless images there is a chance of facing some security threats such as receiving a malicious image. We can use cosign or skopeo for container signing and verifying. You can read more about securing containers with Cosign and Distroless Images in this blog.

Look at using tools like skopeo or crane

You could try some commandline tool like skopeo to fetch the image tags regularly and do some shell magic to notify you on any change you want

You need a containerd on the remote end (Docker and Kubernetes use containerd) and anything that speaks registry API (OCI Distribution spec: https://github.com/opencontainers/distribution-spec) on the client.

You can use skopeo, crane, regclient, BuildKit, anything that speaks OCI-registry on the client. Although you will need to manually run unregistry on the remote host to use them. 'docker pussh' command just automates the workflow.

Just check it out, it's a bash script. You can hack your own way pretty easily.

Shoutout to Michael Crosby, the person in this video, who was instrumental in getting Open Containers (https://opencontainers.org) to v1.0. He was a steady and calm force through a very rocky process.

The Open Container Initiative (OCI) defines standards for container formats and runtimes to ensure consistency and compatibility across different container tools and platforms. It encompasses:

Spin Apps are packaged and distributed as OCI artifacts. By leveraging OCI artifacts, Spin Apps can be distributed using any registry that implements the Open Container Initiative Distribution Specification (a.k.a. “OCI Distribution Spec”).

Docker is a company that maintains the Docker software and also offers a cloud service to run Docker containers in the cloud. They run DockerHub, which is a platform to store share and run Docker images. The actual standard for Docker containers is called OCI (Open Container Initiative). Because Docker is based on OCI there are many other tools that can interact with Docker containers, like Podman or Lima. If you want to go really deep, I really recommend reading the OCI specification! It's long but super interesting.

Open Container Initiative

So performance cannot be said to be better with Docker, why choose Docker then? Better reasons are that you can strip down a Docker image much easier than an OS. This is critical for us due to security requirements. While Python requires a lot of OS features, the majority of the OS is still bloat. Every piece of bloat is a potential attack vector (each of these unused components might have one or more CVEs that we need to patch, even though we don't even use that software). Another reason is that the build process of Docker is much simpler to manage. There are tools such as Packer that allow similar processes for VMs, but these are not as standardized as the open container initiative (OCI - which Docker adheres to).

If you are a CloudFlare employee reading this, you should get involved with the OCI Distribution group that develops the standards for the registry: https://github.com/opencontainers/distribution-spec