Learn a step‑by‑step process for migrating Kubernetes clusters (v1.24+) from the deprecated Docker runtime to the native Containerd CRI, covering compatibility checks, node preparation, installation, configuration, node draining, kubelet updates, validation, and common pitfalls such as cgroup driver mismatches.
Kubernetes 1.24 removed the Docker shim, prompting users to adopt Containerd, and this article compares Docker and Containerd commands, logs, configuration differences, and CNI networking, highlighting how Containerd interacts directly via CRI and reduces bugs.
This article explains how the kubectl command interacts with the Kubernetes control plane, detailing one‑way HTTPS requests and two‑way WebSocket communications, and walks through the full execution flow of a kubectl exec command across kube‑api‑server, kubelet, and the CRI runtime.
When a new Pod is created, Kubelet coordinates with the CRI and CNI components to set up the sandbox, configure networking, pull images, create and start containers, using gRPC calls and command‑line interactions, with details varying across container runtimes such as containerd, cri‑o, and Docker.
Kubernetes 1.24 officially deprecated Dockershim in favor of containerd, explaining the reasons, the underlying container runtime components, the changes in pod creation workflow, the impact on users and operators, and providing practical migration steps and best‑practice recommendations.
Container runtimes are essential for managing containers in Kubernetes, and this article explains their core functions, compares Docker and containerd, details the CRI interface, explores supported backends, and provides practical command references to help you choose the optimal runtime for cloud‑native deployments.
Starting with Kubernetes v1.24 the built‑in dockershim is removed, requiring users to switch to a CRI‑compatible runtime such as containerd or CRI‑O—or install cri‑dockerd for Docker compatibility—while updating scripts, logs, and tooling, and using crictl or ctr for debugging and managing containers and pods.
This proposal introduces in‑place vertical scaling for Pods by making PodSpec resources mutable, extending PodStatus with ResourcesAllocated, adding ResizePolicy and Resize fields, and updating the CRI UpdateContainerResources and ContainerStatus APIs to support live CPU and memory adjustments without restarting containers.
This article explains the technical reasons behind Kubernetes' decision to deprecate Docker, covering the introduction of the CRI shim, the rise of containerd, the phased removal of dockershim, and why Docker remains relevant in the cloud‑native ecosystem.
This article provides a comprehensive overview of Docker's evolution, its modern architecture involving containerd, runc, and CRI, explains how containers are created and managed, and offers step‑by‑step instructions for installing, configuring, and operating containerd with the ctr command‑line tool on Linux.
This article explains the evolution of container runtimes, distinguishing low‑level and high‑level runtimes, introduces key projects such as runC, containerd, CRI‑O, and demonstrates practical demos and CRI integration with Kubernetes, providing code examples and architectural diagrams for cloud‑native practitioners.
CRI shim is a gRPC server that implements the Container Runtime Interface, enabling kubelet to manage pod and container lifecycles, network via CNI, and streaming APIs like Exec, Attach, and PortForward, with detailed explanations of RuntimeService, ImageService, and the CRI‑containerd architecture.
This article explains the internal components of the kubelet, details the CRI architecture, outlines the roles of the Runtime and Image services, and provides code examples of the gRPC API definitions, helping readers grasp how Kubernetes manages containers and images.
This article provides a detailed analysis of the kubelet CRI pod creation workflow, using the dockershim implementation as an example, and includes step‑by‑step code walkthroughs of SyncPod, sandbox creation, and the interactions between kubelet, CRI shim, Docker, and CNI.
The article explains the history of containers, the role of Docker and Kubernetes, why Kubernetes is deprecating Docker's dockershim, the timeline for the change, its impact on users, and the steps required to migrate to OCI‑compatible runtimes such as containerd or CRI‑O.
This article provides a detailed overview of Docker’s evolution, the role of containerd, runc, and CRI in modern container runtimes, explains how Docker delegates container lifecycle management to containerd‑shim, and offers step‑by‑step instructions for installing, configuring, and using containerd with its CLI tools on Linux.
This article walks through every component that processes a simple `kubectl run` command, from the client’s request parsing, through API‑server authentication, authorization, admission control, controller manager scheduling, to kubelet’s CRI and CNI handling that finally creates the pod and its containers.
This article walks through the complete internal journey of a `kubectl run nginx --image=nginx --replicas=3` command, detailing how the request is validated, authenticated, authorized, processed by the API server, passed through initializers, scheduled, and finally materialized as running pods by kubelet, with code excerpts from Kubernetes v1.21.
This article explains the evolution and inner workings of Kubernetes container runtimes, detailing the roles of CRI, OCI, Docker, containerd, CRI‑O, and strong‑isolation solutions like Kata, gVisor, and Firecracker, and why the default dockershim remains prevalent.
This article explains the rationale behind Kubernetes' decision to remove Dockershim, outlines the role of the Container Runtime Interface (CRI), compares Docker's feature set with CRI requirements, and discusses the impact on extensibility and future container runtimes.
The article explains the background of containers, the role of Docker as a runtime, why Kubernetes is deprecating Docker in favor of CRI‑compatible runtimes, the migration path, and what developers and cluster operators need to know to adapt to the change.
This article explains what containerd is, compares it with Docker, describes Kubernetes' CRI support, and provides step‑by‑step commands for using containerd via crictl, showing that migrating from Docker to containerd is simple and resource‑efficient.
This article walks through every stage of how Kubernetes creates a pod—from submitting the YAML to the API, through etcd storage, scheduling, kubelet and CRI actions, CNI networking, and endpoint setup for services—providing a clear, step‑by‑step visual guide.
This article explains the evolution and inner workings of Kubernetes container runtimes, covering the classic Docker‑based flow, the roles of CRI, OCI, containerd, CRI‑O, and strong‑isolation solutions like Kata, gVisor, and Firecracker, while clarifying why the architecture became so layered.
Kubernetes has officially deprecated Docker support by removing the dockershim bridge, explaining that Docker lacks native CRI compliance, and recommends migrating to CRI‑compatible runtimes such as containerd or CRI‑O while clarifying the differences between CRI and OCI runtimes.
Kubernetes has removed Docker support by deprecating the dockershim bridge, urging users to adopt CRI‑compatible runtimes such as containerd or CRI‑O, and explaining the differences between CRI and OCI runtimes, their security implications, and migration recommendations.
This article explains how Kubernetes networking components—including the container runtime, CRI, CNI plugins, Flannel, and node IPAM—work together to assign unique IP addresses to each Pod across a cluster, covering both same‑host and cross‑host communication mechanisms.
This article explains the origins and design of Kubernetes' Container Runtime Interface (CRI), how it abstracts container runtimes, details its lifecycle and streaming operations, reviews major implementations like CRI‑containerd and CRI‑O, and introduces essential debugging tools.
This article explores the evolution and architecture of Kubernetes container runtimes, detailing Docker, containerd, CRI‑O, OCI standards, strong‑isolation solutions like Kata, gVisor and firecracker, and their implications for security and serverless workloads.
Zhang Lei’s KubeCon 2018 talk explains Kubernetes’ interface‑driven design, the role of CRI, container runtimes like containerd and KataContainers, and introduces the containerd ShimV2 layer that simplifies integrating secure, VM‑based runtimes into Kubernetes without writing separate CRI shims.
This article explains the motivation behind the Kubernetes Container Runtime Interface (CRI), outlines its design, and provides a detailed walkthrough of PouchContainer’s CRI manager architecture, including pod creation, network configuration, and I/O stream handling, with code examples and configuration snippets.
