Open Container Initiative-based implementation of Kubernetes Container Runtime Interface
CRI-O - OCI-based implementation of Kubernetes Container Runtime Interface
Compatibility matrix: CRI-O ⬄ Kubernetes
CRI-O follows the Kubernetes release cycles with respect to its minor versions
(1.x.y
). Patch releases (1.x.z
) for Kubernetes are not in sync with those from
CRI-O, because they are scheduled for each month, whereas CRI-O provides
them only if necessary. If a Kubernetes release goes End of
Life,
then the corresponding CRI-O version can be considered in the same way.
This means that CRI-O also follows the Kubernetes n-2
release version skew
policy when it comes to feature graduation, deprecation or removal. This also
applies to features which are independent from Kubernetes. Nevertheless, feature
backports to supported release branches, which are independent from Kubernetes
or other tools like cri-tools, are still possible. This allows CRI-O to decouple
from the Kubernetes release cycle and have enough flexibility when it comes to
implement new features. Every feature to be backported will be a case by case
decision of the community while the overall compatibility matrix should not be
compromised.
For more information visit the Kubernetes Version Skew Policy.
CRI-O Kubernetes Maintenance status
main
branch
master
branch
Features from the main Kubernetes repository are actively implemented
release-1.x
branch (v1.x.y
)
release-1.x
branch (v1.x.z
)
Maintenance is manual, only bugfixes will be backported.
The release notes for CRI-O are hand-crafted and can be continuously retrieved from our GitHub pages website.
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:
What is not in the scope of this project?
CRI-O 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:
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.
Roadmap
A roadmap that describes the direction of CRI-O can be found here. The project is tracking all ongoing efforts as part of the Feature Roadmap GitHub project.
Commands
Command Description
crio(8) OCI Kubernetes Container Runtime daemon
Examples of commandline tools to interact with CRI-O (or other CRI compatible runtimes) are Crictl and Podman.
Configuration
File Description
crio.conf(5) CRI-O Configuration file
policy.json(5) Signature Verification Policy File(s)
registries.conf(5) Registries Configuration file
storage.conf(5) Storage Configuration file
Security
The security process for reporting vulnerabilities is described in SECURITY.md.
OCI Hooks Support
You can configure CRI-O to inject OCI Hooks when creating containers.
CRI-O Usage Transfer
We provide useful information for operations and development 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 a channel on the Kubernetes slack that everyone is welcome to join and chat about development.
Awesome CRI-O
We maintain a curated list of links related to CRI-O. Did you find something interesting on the web about the project? Awesome, feel free to open up a PR and add it to the list.
Getting started Installing CRI-O
To install CRI-O
, you can follow our installation guide.
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 as part of the
cri-o/packaging repository.
Those binaries are available for every successfully built commit on our
Google Cloud Storage Bucket.
This means that the latest commit can be installed via our convenience script:
> curl https://raw.githubusercontent.com/cri-o/packaging/main/get | bash
The script automatically verifies the uploaded sigstore signatures as well, if
the local system has cosign
available in
its $PATH
. The same applies to the SPDX based bill of
materials (SBOM), which gets automatically verified if the
bom tool is in $PATH
.
Besides amd64
, we also support the arm64
and ppc64le
bit architectures.
This can be selected via the script, too:
curl https://raw.githubusercontent.com/cri-o/packaging/main/get | bash -s -- -a arm64
It is also possible to select a specific git SHA or tag by:
curl https://raw.githubusercontent.com/cri-o/packaging/main/get | bash -s -- -t v1.21.0
The above script resolves to the download URL of the static binary bundle tarball matching the format:
https://storage.googleapis.com/cri-o/artifacts/cri-o.$ARCH.$REV.tar.gz
Where $ARCH
can be amd64
or arm64
or ppc64le
and $REV
can be any git SHA or tag.
Please be aware that using the latest main
SHA might cause a race, because
the CI has not finished publishing the artifacts yet or failed.
We also provide a Software Bill of Materials (SBOM) in the SPDX
format for each bundle. The SBOM is available at the same URL
like the bundle itself, but suffixed with .spdx
:
https://storage.googleapis.com/cri-o/artifacts/cri-o.$ARCH.$REV.tar.gz.spdx
Running Kubernetes with CRI-O
Before you begin, you'll need to start CRI-O
You can run a local version of Kubernetes with CRI-O
using local-up-cluster.sh
:
CGROUP_DRIVER=systemd \ CONTAINER_RUNTIME=remote \ CONTAINER_RUNTIME_ENDPOINT='unix:///var/run/crio/crio.sock' \ ./hack/local-up-cluster.sh
For more guidance in running CRI-O
, visit our tutorial page
The HTTP status API
CRI-O exposes per default the gRPC API to fulfill the Container Runtime Interface (CRI) of Kubernetes. Besides this, there exists an additional HTTP API to retrieve further runtime status information about CRI-O. Please be aware that this API is not considered to be stable and production use-cases should not rely on it.
On a running CRI-O instance, we can access the API via an HTTP transfer tool like curl:
$ sudo curl -v --unix-socket /var/run/crio/crio.sock http://localhost/info | jq { "storage_driver": "btrfs", "storage_root": "/var/lib/containers/storage", "cgroup_driver": "systemd", "default_id_mappings": { ... } }
The following API entry points are currently supported:
Path Content-Type Description
/info
application/json
General information about the runtime, like storage_driver
and storage_root
.
/containers/:id
application/json
Dedicated container information, like name
, pid
and image
.
/config
application/toml
The complete TOML configuration (defaults to /etc/crio/crio.conf
) used by CRI-O.
/pause/:id
application/json
Pause a running container.
/unpause/:id
application/json
Unpause a paused container.
The subcommand crio status
can be used to access the API with a dedicated command
line tool. It supports all API endpoints via the dedicated subcommands config
,
info
and containers
, for example:
$ sudo crio status info cgroup driver: systemd storage driver: btrfs storage root: /var/lib/containers/storage default GID mappings (format <container>:<host>:<size>): 0:0:4294967295 default UID mappings (format <container>:<host>:<size>): 0:0:4294967295Metrics
Please refer to the CRI-O Metrics guide.
Tracing
Please refer to the CRI-O Tracing guide.
Container Runtime Interface special cases
Some aspects of the Container Runtime are worth some additional explanation. These details are summarized in a dedicated guide.
Debugging tips
Having an issue? There are some tips and tricks for debugging located in our debugging guide
Adopters
An incomplete list of adopters of CRI-O in production environments can be found here. If you're a user, please help us complete it by submitting a pull-request!
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.
Governance
For more information on how CRI-O is goverened, take a look at the governance file
License Scan
Twice a month we will interview people behind open source businesses. We will talk about how they are building a business on top of open source projects.
We'll never share your email with anyone else.