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The latest version of Kubernetes Kubernetes v1.20.0-rc.0 is now available. The Kubernetes project plans to deprecate Docker Engine support in the kubelet and support for dockershim will be removed in a future release, probably late next year. The net/net is support for your container images built with Docker tools is not being deprecated and will still work as before.

What does this mean for you if you use Docker and Kubernetes?

First of all, don’t panic 🙂 Developers can still use the Docker platform to build, share, and run containers on Kubernetes! This change primarily impacts operators and administrators for Kubernetes and doesn’t impact developer work flows. The images Docker builds are compliant with OCI (Open Container Initiative), are fully supported on containerd, and will continue to run great on Kubernetes.

If you’re using Docker, you’re already using containerd. We build Docker’s runtime upon containerd while providing a great developer experience around it. For production environments that benefit from a minimal container runtime, such as Kubernetes, and may have no need for Docker’s great developer experience, it’s reasonable to directly use lightweight runtimes like containerd.

Docker created the containerd project, along with Google and IBM, in 2016, with the goal of this transition in mind. The deprecation of docker-shim (and Docker Engine as runtime) marks the completion of a long-term commitment to provide a modern runtime for Kubernetes. Containerd was created as a core low-level, extensible runtime for both Docker and Kubernetes to each use in the most appropriate way.

Containerd was donated to the CNCF in 2017, and has grown to incorporate the containerd CRI project to interface with Kubernetes, as well as seeing a host of innovation and investment from across the industry, including from Amazon, Google, Microsoft and IBM.

In 2019 it became a graduated CNCF project, the highest project level, showing its maturity and it remains the only container runtime with this status. Over the last few years the leading Kubernetes service providers such as AWS and Google have migrated to Containerd as their Kubernetes runtime. This process of depreciation now reflects the great success of this work, and of the thriving community around containerd.

Support for your container images built with Docker tools is not being deprecated.

Container images you build using Docker tools will continue to run on Kubernetes. Buildkit, our next generation build infrastructure, has a flexible architecture so that while it can be used as the builder with Docker, it can also talk directly to containerd or runc instead for use in infrastructure where Docker might not be available.

Docker is committed to containerd development: we will continue to further invest, along with the growing buildkit community, in helping you use Docker builds wherever and however your infrastructure is hosted.

You can continue to build and run Docker images locally and in your Kubernetes cluster as this deprecation will not impact that experience.

What is the Kubernetes project deprecating then?

Kubernetes is deprecating dockershim, which is a component in Kubernetes’ kubelet implementation, communicating with Docker Engine. Arnaud Porterie had some great thoughts on this that he shared here.

The Kubernetes project has also published this FAQ.  Kat Cosgrove did a great job explaining the changes very simply here.

Do you need to take action?

Today, and in Kubernetes v1.20, Kubernetes administrators can continue to use docker commands and kubectl commands to manage their Kubernetes clusters.

In a future release of Kubernetes, a few minor releases from now, when support for dockershim is eventually removed, you will no longer be able to use docker commands to inspect your cluster. 

Many of these commands have similar commands in kubectl and ctr (the containerd CLI).  While the commands to inspect your cluster in Kubernetes may change in the future, Developers will still be able to use Docker tools to docker build, docker push and docker run containers and container images on Kubernetes.  

Further Background

KEP-1985: Kubernetes Enhancement Proposal to remove dockershim from Kubelet

Questions? Feedback?

Please reach out on Docker’s slack if you have questions or other feedback. 

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