cri-o/cri-o

CRI-O is a piece of infrastructure software that sits between Kubernetes and the containers it runs. Kubernetes is a system used to manage large numbers of application containers across many servers. To actually start and stop containers, Kubernetes needs to talk to a container runtime, which is the software that does the low-level work of launching isolated processes. CRI-O is one such runtime connector. More specifically, CRI-O implements something called the Container Runtime Interface (CRI), which is the standard Kubernetes uses to communicate with whatever is actually running containers on a given machine. CRI-O translates those instructions into calls to OCI-compliant runtimes, where OCI stands for Open Container Initiative, a set of industry standards for how containers should be defined and run. In practice, CRI-O typically delegates the actual container execution to a tool like runc, which does the final work of starting the isolated process. CRI-O handles a defined set of responsibilities: pulling and managing container images (which can be in Docker or other OCI-compatible formats), managing how image layers are stored on disk, starting and stopping container processes, and providing the monitoring and logging that Kubernetes expects. Building or pushing images is explicitly out of scope for this project. CRI-O follows the Kubernetes release schedule, with each major version of CRI-O corresponding to a matching Kubernetes version. It is an active project under the Kubernetes community and is governed by the sig-node working group. It has a weekly meeting and a public roadmap tracked in a GitHub project. The project is used in production environments, including Red Hat's OpenShift platform. Installation packages are available in deb and rpm formats for common Linux distributions. The README includes a compatibility matrix, configuration reference, debugging tips, and a list of known adopters.