Kubernetes Deprecates Docker: Reasons and Recommended Container Runtimes

Kubernetes has announced that Docker support in kubelet is deprecated and will be removed in future releases; the dockershim module that previously bridged Docker to the CRI API is being phased out.

The primary reason is that Docker does not implement the Container Runtime Interface (CRI) required by Kubernetes, and maintaining the dockershim bridge introduced operational complexity and security concerns.

Although Docker remains a powerful tool for creating development environments, it is not essential for Kubernetes workloads, which rely on the control plane to schedule containers on nodes via a CRI‑compatible runtime.

Kubernetes abstracts various compute resources into a unified pool, and the container runtime (formerly Docker) is only used to launch containers on each node through kubelet.

Docker is being dropped because its extra networking and storage features are unnecessary in the Kubernetes architecture, reducing the attack surface and simplifying runtime management.

Recommended CRI runtimes are containerd , which retains Docker compatibility and provides a full CRI implementation, and CRI‑O , a lightweight, pure‑CRI runtime developed by Red Hat and used in OpenShift.

It is important to distinguish between CRI runtimes (which handle kubelet requests and generate OCI specifications) and OCI runtimes (such as runC or gVisor) that actually create containers using Linux kernel features; gVisor adds an additional security layer but may have performance and compatibility trade‑offs.

In summary, Docker is deprecated in Kubernetes; users should transition to CRI‑compatible runtimes like containerd or CRI‑O, understand the role of OCI runtimes, and choose the solution that best fits their workload and security requirements.