RHCOS 10 - Red Hat’s new worker node OS for OpenShift

Context

Red Hat OpenShift uses a purpose-built, immutable operating system for cluster nodes, commonly known as Red Hat Enterprise Linux CoreOS (RHCOS). This operating system, which uses the same kernel and hardware compatibility from Red Hat Enterprise Linux (RHEL), ships with a minimal-footprint operating environment, with its configuration entirely orchestrated by OpenShift and Kubernetes-based APIs.

Starting in Q4 2026, OpenShift will ship the newest iteration of this operating system, RHCOS 10, by default for new installations, and all certified ISV containers and operators are expected to support it.

RHCOS 10 is available as a Technology Preview in OpenShift 4.21 and 4.22 already. RHCOS 9 will remain available for newer OpenShift versions at least into mid 2027.

Certification requirements

When RHCOS 10 becomes generally available in Q4 2026, all certified offerings on OpenShift are required to support it. Containers that have privileged host access and interact with the host OS are strongly encouraged to perform additional testing. Please see Red Hat Enterprise Linux Container Compatibility Matrix for more information. Containers that fall into this class are typically CSI or CNI drivers, host agents, provide kernel drivers, or alter configuration files, which may need changes to remain compatible with RHEL 10. Workloads that have no privileged host access should not encounter issues, but testing is still recommended.

How to test RHCOS 10 now

OpenShift 4.21 and 4.22 provide an early Tech Preview of both RHCOS 10 support and a feature we’re currently calling OS Streams. You may test these features today in OpenShift 4.21 or 4.22 (make sure you use the latest patch release) or later in either a new install or in an existing cluster. Note, however, that enabling Tech Preview features will make the cluster ineligible for future minor version upgrades. You should test this only in clusters that you’re willing to tear down at the end of your testing. Please follow the instructions in this Knowledgebase Article to start testing: https://access.redhat.com/articles/7139678 

Compatibility implications

Aside from the goals outlined above, it will be important to understand the implications of RHCOS major version changes.

OpenShift nodes that upgrade to RHCOS 10 will no longer support containers based on UBI7. Nodes that continue running RHCOS 9 will remain compatible with UBI7; however, partners are encouraged to transition certified workloads to UBI9 or later if they haven’t already. If FIPS140-compatibility is required, the recommended base image is UBI9, as the RHEL 10/UBI10 cipher libraries are still being FIPS140-certified.

RHCOS 10, being based on RHEL 10, drops support for x86_64 v2 or earlier instruction sets. That means that only systems that support x86_64 v3 or newer are supported. It’s worth noting that most hardware vendors certify their hardware on at least 2, if not 3 major RHEL versions. Only the oldest hardware, likely certified on RHEL 8 and RHEL 9 (and possibly RHEL 7), will not receive RHEL 10 certification. Please familiarize yourself with your hardware’s certification status if that is relevant to you. You may look it up at https://catalog.redhat.com/en/search?searchType=Hardware 

Reporting issues

We’re also providing this early access to RHCOS 10 so that customers and partners alike can test early and let us know of any issues that arise. Please engage through your partner management contact for any feedback.