cri-o - OCI-based implementation of Kubernetes Container Runtime Interface

Status: pre-alpha

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 backwards 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.

Getting started

Prerequisites

runc version 1.0.0.rc1 or greater is expected to be installed on the system. It is picked up as the default runtime by ocid.

Build

btrfs-progs-devel, device-mapper-devel, glib2-devel, glibc-devel, glibc-static, gpgme-devel, libassuan-devel, libgpg-error-devel, and pkgconfig packages on CentOS/Fedora or btrfs-tools, libassuan-dev, libc6-dev, libdevmapper-dev, libglib2.0-dev, libgpg-error-dev, libgpgme11-dev, and pkg-config on Ubuntu or equivalent is required. In order to enable seccomp support you will need to install development files for libseccomp on your platform.

e.g. libseccomp-devel for CentOS/Fedora, or libseccomp-dev for Ubuntu In order to enable apparmor support you will need to install development files for libapparmor on your platform. e.g. libapparmor-dev for Ubuntu

$ GOPATH=/path/to/gopath
$ mkdir $GOPATH
$ go get -d github.com/kubernetes-incubator/cri-o
$ cd $GOPATH/src/github.com/kubernetes-incubator/cri-o
$ make install.tools
$ make
$ sudo make install

Otherwise, if you do not want to build cri-o with seccomp support you can add BUILDTAGS="" when running make.

# create a 'github.com/kubernetes-incubator' in your $GOPATH/src
cd github.com/kubernetes-incubator
git clone https://github.com/kubernetes-incubator/cri-o
cd cri-o

make BUILDTAGS=""
sudo make install

Build Tags

cri-o supports optional build tags for compiling support of various features. To add build tags to the make option the BUILDTAGS variable must be set.

make BUILDTAGS='seccomp apparmor'

Build Tag	Feature	Dependency
seccomp	syscall filtering	libseccomp
selinux	selinux process and mount labeling
apparmor	apparmor profile support	libapparmor

Running pods and containers

Follow this tutorial to get started with CRI-O.

Setup CNI networking

A proper description of setting up CNI networking is given in the contrib/cni README. But the gist is that you need to have some basic network configurations enabled and CNI plugins installed on your system.

Running with kubernetes

You can run the local version of kubernetes using local-up-cluster.sh. After starting ocid daemon:

EXPERIMENTAL_CRI=true CONTAINER_RUNTIME=remote CONTAINER_RUNTIME_ENDPOINT='/var/run/ocid.sock --runtime-request-timeout=15m' ./hack/local-up-cluster.sh

For running on kubernetes cluster - see the instruction

Current Roadmap

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