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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
On Fedora/Centos/RHEL:
dnf install -y btrfs-progs-devel device-mapper-devel libseccomp-devel glib2-devel glibc-devel glibc-static gpgme-devel libassuan-devel libgpg-error-devel pkgconfig libselinux-devel
On Ubuntu/Debian:
apt install btrfs-tools libassuan-dev libc6-dev libdevmapper-dev libglib2.0-dev libgpg-error-dev libgpgme11-dev pkg-config libseccomp-dev libapparmor-dev
$ export GOPATH=~/go
$ 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
- Basic pod/container lifecycle, basic image pull (already works)
- Support for tty handling and state management
- Basic integration with kubelet once client side changes are ready
- Support for log management, networking integration using CNI, pluggable image/storage management
- Support for exec/attach
- Target fully automated kubernetes testing without failures