Image Mode: The Supported Way to Extend RHEL CoreOS - DevConf.IN 2026

Описание: Title: Image Mode: The Supported Way to Extend RHEL CoreOS

Speaker(s): Prachiti Prakash Talgulkar

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OpenShift relies on Red Hat Enterprise Linux CoreOS (RHCOS) as its foundation. RHCOS is tightly integrated with the rest of the platform and designed to be consistent, secure, and predictable during upgrades. But in real clusters, teams often need just a little more flexibility, maybe a custom driver, a small troubleshooting tool, or a monitoring agent that isn’t part of the default OS. Because RHCOS is immutable, these needs have historically been difficult to support

Image mode, also known as On-Cluster Layering (OCL), changes this. Image mode brings a cloud-native approach to OS management by treating the OS just like a container image: you define your configuration as code, build a unified OS image inside the cluster, and roll it out across nodes with the same safety and consistency OpenShift is known for. Need to add an agent? A driver? A tool? Apply a hotfix? Image mode makes these customizations fully supported, upgrade-safe, and declarative, without external pipelines or custom OS builds. Even with limitations, such as how `/var` is handled, image mode gives clear guidance on where and how to add custom content.

This talk introduces image mode from the ground up: what it is, how it works, and why it matters. We’ll walk through its architecture, the MachineOSConfig workflow, the in-cluster build process, and what the experience looks like for administrators and customers. Whether you’re enabling a critical operational tool or supporting a specialized workload, image mode provides a reliable, modern way to customize RHCOS while keeping your cluster stable and easy to manage.

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Full schedule, including slides and other resources:
https://pretalx.devconf.info/devconf-...