What’s new in CRI-O 1.31

Posted on September 12, 2024 by Sascha Grunert

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Project post originally published on Github by Sascha Grunert

The CRI-O maintainers are happy and proud to announce that CRI-O v1.31.0 has been released! This brand new version contains a large list of cool new features, bug fixes and smaller enhancements. I would like to take the opportunity to guide you through CRI-O’s latest and greatest enhancements in the field of Kubernetes compliant container runtimes.

New features

The CRI-O community voted to use the OCI runtime crun as new default in replacement to runc. That’s actually not too new, because crun has been used as default runtime in the packages and static binary bundles for quite a while. The runtime offers an overall better performance and lower memory footprint than runc. It’s efficiency in terms of faster container start times and lower memory usage makes it a more optimized runtime for modern workloads, for example when it comes to edge use cases as well as running WebAssembly (Wasm) workloads.

CRI-O v1.31 also features support for fine-grained SupplementalGroups (KEP-3619), which allow to control and track how supplemental groups are applied to a container process. If you like to learn more about the feature itself, then feel free to read through the corresponding Kubernetes v1.31 blog post.

Beside that, the CRI-O maintainers also added support for the Kubernetes image volume source alpha feature (KEP-4639). This feature allows users to utilize OCI images and artifacts as custom volume source and mount them into containerized workloads. There is another Kubernetes v1.31 blog post available which covers more details about the functionality and usage of the feature.

CRI-O now supports sigstore (cosign) signature verification for policies corresponding to a certain Kubernetes namespace. This means, that policies in the (default) directory /etc/crio/policies/[NAMESPACE].json will be validated for each pod of the corresponding NAMESPACE. This will also happen on container creation, which is a huge step forward in enforcing sigstore policies for a dedicated Kubernetes namespace in comparison to policies which only apply to the whole cluster itself.

Beside the support for bigger Kubernetes features, CRI-O v1.31 ships a bunch of cool smaller enhancements, for example:

• Adding a --no-sync-log/no_sync_log option to disable fsync on container log rotation and container exit. This can improve performance at the cost of potential data loss on machine crashes.
• Respecting the image pull timeout set by the RPC context to potentially abort an ongoing image pull.
• Adding /dev/net/tun to the default allowed devices, which helps users to run Podman inside containers.
• Showing the current runtime configuration in the CRI-O logs for maximum transparency with respect to the loaded in-memory configuration.
• Updating the type of checks the internal repair feature performs on CRI-O’s start-up following an unclean shutdown. This also features the new crio check subcommand.
• Updating the default pause image to v3.10 to stay up to date with Kubernetes v1.31.
• Adding support for conmon-rs > v0.6.5, which is a replacement for the required container monitor conmon.
• Moving the tracing profile and endpoint listener to use 127.0.0.1 as the new default to strengthen the security footprint of the project.
• CRI-O now removes a container after it fails to start. This helps to prevent copies of it from piling up until it succeeds.

Deprecations and removals

It’s worth to mention some deprecations and removals in CRI-O v1.31 which may affect existing users:

• CRI-O v1.31 removed the registries config in crio.image as well as the --registry CLI argument which have been already deprecated.
• The device mapper storage driver is not supported any more.
• The crio config --migrate-defaults subcommand has been removed (deprecated in v1.28).

And more

Beside features and removals, the CRI-O maintainers fixed bugs and addressed CVE’s to ensure CRI-O’s stability over the past releases. A full list of them can be found in the official release notes.

I would like to take this opportunity to give a huge shoutout to all contributors and maintainers of the CRI-O for this awesome job! 🙌

If you want to give CRI-O v1.31 a try, then feel free to head over to our official packaging repository, which supports mostly all deb and rpm based distributions.

If you have any questions or feedback, feel free to reach out using the Kubernetes Slack #crio channel or create an issue in the official repository.