cri-o VS runc

Kubernetes on the backend used to utilize docker for much of its container runtime solutions. One of the modular features of Kubernetes is the ability to utilize a Container Runtime Interface or CRI. The problem was that Docker didn't really meet the spec properly and they had to maintain a shim to translate properly. Instead users could utilize the popular containerd or cri-o runtimes. These follow the Open Container Initiative or OCI's guidelines on container formats.

Multiple container runtimes are supported, like conatinerd, cri-o, or other CRI compliant runtimes.

Install container runtime on all nodes. We will use cri-o.

Container Runtime Interface (CRI) is one of the important parts of the Kubernetes cluster. It is a plugin interface allowing kubelet to use different container runtimes. And recently CRI-O container runtime has been announced as a CNCF Graduated project. I thought of writing a blog on CRI-O and how to set up a single-node Kubernetes cluster with Kubeadm and CRI-O.

CRI-O: This is an open-source container runtime designed for use with Kubernetes. It is a lightweight and stable environment for containers. It also complies with the Kubernetes Container Runtime Interface (CRI), making it easy to integrate with Kubernetes.

With CRI-O I believe you can configure registry mirror locations…. Similar to this: https://github.com/cri-o/cri-o/issues/4941

Alternatives like Podman and CRI-O continue to gain traction and may replace Docker in various places. For example, Kubernetes used to use Docker, then moved to containerd, and now also support CRI-O. Generally speaking, the core features of "Docker" are such a commodity now that no one was the wiser when Kubernetes stopped using it.

will the site be available for the CKA exam? https://github.com/cri-o/cri-o/blob/main/install.md

The CRI-O container engine provides a stable, more secure, and performant platform for running Open Container Initiative (OCI) compatible runtimes. CRI-Os purpose is to be the container engine that implements the Kubernetes Container Runtime Interface (CRI) for OpenShift Container Platform and Kubernetes, replacing the Docker service. Source

I can speak to this. Containers, and by extension k8s, break a well known security boundary that has existed for a very long time - whether you are using a real (hardware) server or a virtual machine on the cloud if you pop that instance/server generally speaking you only have access to that server. Yeh, you might find a db config with connection details if you landed on say a web app host but in general you still have to work to start popping the next N servers.

That's not the case when you are running in k8s and the last container breakout was just announced ~1 month ago: https://github.com/opencontainers/runc/security/advisories/G... .

At the end of the day it is simply not a security boundary. It can solve other problems but not security ones.

It's interesting that, in light of things like this, you still see large software companies adding support for new components written in non-memory safe languages (e.g. C)

As an example Red Hat OpenShift added support for crun(https://github.com/containers/crun) this year(https://cloud.redhat.com/blog/whats-new-in-red-hat-openshift...), which is written in C as an alternative to runc, which is written in Go(https://github.com/opencontainers/runc)...

Rabbit hole indeed. That wasn't related to my job at the time, lol. The job change came with a company-provided computer and that put an end to the tinkering.

BTW, I found my hacks to make runc run on Chromebook: https://github.com/opencontainers/runc/compare/main...gabrys...

being the main author of crun, I can clarify that statement: I am not a fan of Go _for this particular use case_.

Using C instead of Go avoided a bunch of the workarounds that exists in runc to workaround the Go runtime, e.g. https://github.com/opencontainers/runc/blob/main/libcontaine...

runc

Not OP, but if I had to guess, a lot of this can be picked up by just observing common security issues in the Linux space, since similar mistakes and oversights have caused quite a few real-world CVEs in the past, e.g. this random example of a TOCTTOU vulnerability in runc.