Initially, Kubernetes was tightly coupled with Docker as its default container runtime. However, as the ecosystem evolved, there was a need to support multiple container runtimes without making Kubernetes dependent on any single implementation. This is where the Container Runtime Interface (CRI) comes into play.
CRI is an API specification that defines how Kubernetes communicates with container runtimes. It abstracts the details of the container runtime, providing a standardized way for the kubelet to perform operations like:
> Launching containers: Starting and stopping containers as pods are scheduled and terminated.
> Managing images: Pulling container images from registries and handling image storage.
> Monitoring container health: Checking the status and health of running containers.
CRI allows Kubernetes to support multiple container runtimes seamlessly. As long as a runtime implements the CRI, Kubernetes can interact with it without any additional modifications or specific integrations.
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A) CRI is not an implementation but an interface. containerd and CRI-O are implementations of the CRI, not higher-level orchestration tools.
C) CRI is not a set of command-line tools. It’s an API specification. containerd and CRI-O are full-fledged container runtimes, not merely libraries.
D) CRI is not a security specification. It focuses on defining how Kubernetes interacts with container runtimes, not on security isolation mechanisms.