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Comment by spicyusername | Hacker News Reader

Podman is for running containers on a single host. It's exactly like docker with a few additional features (like the ability to run rootless containers and run containers in something like a Kubernetes pod). Podman was developed by Red Hat to replace docker, the cli, because Docker, the company, didn't play very nice with the open source community.

Rancher is a Kubernetes implementation that can run containers across multiple hosts. Rancher is more comparable to something like Red Hat OpenShift or Hashicorp Nomad than docker.

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> Podman was developed by Red Hat

Wow they should advertise that more. I had no idea and I'm pretty deep in the Red Hat ecosystem.

Why should they? I work for Red Hat, help and contribute to podman but they like to remain as 'independent' as possible. We collaborate but the preference is that Podman is an upstream/community project first.

Pretty sure they will once it's a bit more stable. They have presented at most of the kubecons for several years but it's always cautioned they will potentially break stuff.

I think OP meant Rancher Desktop, which is meant to be a replacement of sorts for Docker Desktop (it does include a Kubernetes implementation though)

Does Kubernetes usage also require podman or docker?

Kubernetes needs a container runtime, of which docker is a supported type (but deprecated and replaced with containerd for most users): https://kubernetes.io/docs/setup/production-environment/cont...

Kubernetes requires a tool which implements the Container Runtime Interface (CRI), a standardized API for starting & managing containers. This is from 2015-2016[1]. The CRI interface is defined by & owned by Kubernetes, and there's a lot of implementations: runc, crun, youki, dockershim and likely more.

For a while Kubernetes has included something called the "dockershim", it's own implementation of a CRI interface that, under the hood, calls Docker or Podman, so Kubernetes "pods" run in Docker/Podman. There's also tools like Kind[3] ("kubernetes in docker") that go further- not just hosting Kubernetes worker containers in Docker, but hosting the main kubernetes daemons also in Docker.

Kubernetes deprecated Dockershim, formally in December 2020, but is just throwing the switch now in the upcoming 1.24, expected mid-April[4]. A company Mirantis has pledged to take over support of Dockershim[5], and is calling the new effort "cri-dockerd"[6]. This should allow Kubernetes workers to continue to run via Docker or Podman.

Kind is unaffected, since it runs the main Kubernetes controllers in Docker, which then launch their own opencontainerd (one off the main CRI implementations) inside that Docker container, nested like, so no dockership/cri-dockerd is needed).

Worth re-noting that Podman includes tools to try to run Kubernetes pods directly, without running the rest of Kubernetes.

[1] https://kubernetes.io/blog/2016/12/container-runtime-interfa...

[2] https://github.com/kubernetes/cri-api

[3] https://kind.sigs.k8s.io/

[4] https://kubernetes.io/blog/2022/01/07/kubernetes-is-moving-o...

[5] https://www.mirantis.com/blog/mirantis-to-take-over-support-...

[6] https://github.com/Mirantis/cri-dockerd

Most modern Kubernetes implementations use either containerd or cri-o.

Kubernetes can support multiple solutions if I am not mistaken.

I know rancher requires Docker and is not compatible with Podman as of today.

And I believe Red Hat uses Podman in Openshift, their implementation of kubernetes.

Podman is only used for bootstrapping the cluster with the OpenShift installer. The cluster itself uses cri-o.

OpenShift uses cri-o as the runtime.

Kubernetes can use either

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