CRI-O - OCI-based implementation of Kubernetes Container Runtime Interface

Status: Stable

Compatibility matrix: CRI-O <-> Kubernetes clusters

CRI-O and Kubernetes follow the same release cycle and deprecation policy. For more information visit the Kubernetes versioning documentation.

Version - Branch	Kubernetes branch/version	Maintenance status
CRI-O 1.12.x - release-1.12	Kubernetes 1.12 branch, v1.12.x	=
CRI-O 1.13.x - release-1.13	Kubernetes 1.13 branch, v1.13.x	=
CRI-O 1.14.x - release-1.14	Kubernetes 1.14 branch, v1.14.x	=
CRI-O HEAD - master	Kubernetes master branch	✓

Key:

• ✓ Changes in main Kubernetes repo about CRI are actively implemented in CRI-O
• = Maintenance is manual, only bugs will be patched.

What is the scope of this project?

CRI-O is meant to provide an integration path between OCI conformant runtimes and the kubelet. Specifically, it implements the Kubelet Container Runtime Interface (CRI) using OCI conformant runtimes. The scope of CRI-O is tied to the scope of the CRI.

At a high level, we expect the scope of CRI-O to be restricted to the following functionalities:

• Support multiple image formats including the existing Docker image format
• Support for multiple means to download images including trust & image verification
• Container image management (managing image layers, overlay filesystems, etc)
• Container process lifecycle management
• Monitoring and logging required to satisfy the CRI
• Resource isolation as required by the CRI

What is not in scope for this project?

• Building, signing and pushing images to various image storages
• A CLI utility for interacting with CRI-O. Any CLIs built as part of this project are only meant for testing this project and there will be no guarantees on the backward compatibility with it.

This is an implementation of the Kubernetes Container Runtime Interface (CRI) that will allow Kubernetes to directly launch and manage Open Container Initiative (OCI) containers.

The plan is to use OCI projects and best of breed libraries for different aspects:

• Runtime: runc (or any OCI runtime-spec implementation) and oci runtime tools
• Images: Image management using containers/image
• Storage: Storage and management of image layers using containers/storage
• Networking: Networking support through use of CNI

It is currently in active development in the Kubernetes community through the design proposal. Questions and issues should be raised in the Kubernetes sig-node Slack channel.

Commands

Command	Description	Demo
crio(8)	OCI Kubernetes Container Runtime daemon

Note that kpod and its container management and debugging commands have moved to a separate repository, located here.

Configuration

File	Description
crio.conf(5)	CRI-O Configuation file
policy.json(5)	Signature Verification Policy File(s)
registries.conf(5)	Registries Configuration file
storage.conf(5)	Storage Configuation file

OCI Hooks Support

You can configure CRI-O to inject OCI Hooks when creating containers.

CRI-O Usage Transfer

Useful information for ops and dev transfer as it relates to infrastructure that utilizes CRI-O

Communication

For async communication and long running discussions please use issues and pull requests on the github repo. This will be the best place to discuss design and implementation.

For chat communication we have an IRC channel #CRI-O on chat.freenode.net, and a channel on the kubernetes slack that everyone is welcome to join and chat about development.

Getting started

Installing CRI-O

To install CRI-O, you can use your distrobutions package manager:

Fedora, CentOS, RHEL, and related distributions: sudo yum install crio openSUSE: sudo zypper install cri-o

Debian, Ubuntu, and related distributions:

sudo apt-add-repository ppa:projectatomic/ppa
sudo apt-get install crio

Alternatively, if you'd rather build CRI-O from source, checkout our setup guide. We also provide a way in building static binaries of CRI-O via nix.

Running CRI-O

You can run a local version of kubernetes with CRI-O using local-up-cluster.sh:

1. Clone the kubernetes repository
2. From the kubernetes project directory, run:

CGROUP_DRIVER=systemd \
CONTAINER_RUNTIME=remote \
CONTAINER_RUNTIME_ENDPOINT='unix:///var/run/crio/crio.sock  --runtime-request-timeout=15m' \
./hack/local-up-cluster.sh

For more guidance in running CRI-O, visit our tutorial page

Current Roadmap

1. Basic pod/container lifecycle, basic image pull (done)
2. Support for tty handling and state management (done)
3. Basic integration with kubelet once client side changes are ready (done)
4. Support for log management, networking integration using CNI, pluggable image/storage management (done)
5. Support for exec/attach (done)
6. Target fully automated kubernetes testing without failures e2e status (done)
7. Track upstream k8s releases (active)

Weekly Meeting

A weekly meeting is held to discuss CRI-O development. It is open to everyone. The details to join the meeting are on the wiki.