Kairos v4.1.0: From Image Build to Managed Nodes with AuroraBoot

Kairos v4.1.0 is now available.

This release improves the path from building a Kairos image to deploying and managing real nodes. kairos-agent now includes phone-home support, which works together with AuroraBoot v0.20.0 and its web UI when you run it in fleet server mode. Nodes produced through that flow can come online, report back after first boot using phone-home, and show up in AuroraBoot’s node manager.

Behind that story, v4.1.0 also ships Hadron v0.2.0 for Hadron-based Kairos images, Ubuntu 26.04 support in kairos-init, boot and install/disk hardening, broader distro compatibility, and release automation improvements. These layers all support the same operational direction: a dependable lifecycle around immutable images.

From image creation to managed nodes

Kairos v4.1.0 adds phone-home support in kairos-agent. On its own, that gives nodes a way to signal back after installation or first boot. AuroraBoot v0.20.0, which is a separate project that works alongside Kairos, adds an end-to-end node build and deployment flow through its web UI.

AuroraBoot can run as a self-hosted fleet server: a single deployment that brings together a dashboard, REST API, node manager, SecureBoot key store, and netboot server. The web UI walks you through building an artifact, deploying it, and managing nodes after they appear.

Nodes built through AuroraBoot can phone home automatically on first boot (via kairos-agent) and land in the Nodes list in AuroraBoot. From there, you can drive actions such as upgrade, reboot, reset, applying cloud-config, or running allowed commands.

That combination matters because image-based systems are not only about producing a bootable image. They also need a reliable operational path from image creation through installation, first boot, registration, and ongoing lifecycle management. kairos-agent and AuroraBoot address that gap as complementary pieces: Kairos on the node, AuroraBoot in the control plane you choose to run.

Hadron-based images now use Hadron v0.2.0

Hadron-based Kairos images move to Hadron v0.2.0, updating the minimal Linux foundation those images are built on. This is an important supporting change for anyone using the official Hadron-based artifacts, but it sits alongside the broader provisioning and lifecycle work above.

Hadron remains the upstream-first base we use for a smaller, more controlled foundation while lifecycle, provisioning, and Kubernetes integration stay in the Kairos layer.

Hadron v0.2.0 includes updates such as:

• Linux kernel updated to 7.0.6
• DirtyFrag mitigation by blocklisting the affected nf_defrag_ipv4 and nf_defrag_ipv6 kernel modules by default
• Thor GPU image example and documentation
• Additional ARM64 Nvidia kernel configuration
• GRUB SMBIOS support
• Parameterized Dockerfile base image and tag support
• RISC-V images included in Hadron’s multi-architecture manifests

RISC-V caveat: Hadron v0.2.0 publishes RISC-V in its multi-architecture manifests as groundwork for the ecosystem. Kairos does not publish RISC-V artifacts yet, so this is not a user-testable Kairos target today—only preparation for future work.

Ubuntu 26.04 support

For users building Kairos from existing distribution bases, v4.1.0 adds support for Ubuntu 26.04 in kairos-init.

This continues one of the core Kairos ideas: users should be able to bring their own base image while still getting an image-based, Kubernetes-native lifecycle model on top.

Kairos is not tied to a single Linux distribution. Instead, it provides the tooling and lifecycle model around different bases, whether that is Ubuntu, Fedora, Alpine, openSUSE, Debian, Rocky, or Hadron.

Better boot flows

Kairos v4.1.0 includes several boot-related improvements.

immucore now includes TPM kernel module support during UKI boot, and kairos-agent improves systemd-boot support with assessment suffix handling.

These are lower-level changes, but they matter for the direction of the project. Image-based systems are not only about producing a bootable artifact. They also need reliable boot flows, recovery paths, and support for more trusted and measured boot scenarios.

More robust install and disk handling

This release also includes a set of practical improvements around installation and disk handling.

Notable changes include:

• support for resolving script:// disk paths through the yip helper
• JSON schema updates for the new script:// disk schema
• flexible disk improvements in yip
• a fix for bytes-vs-sectors mismatch in partition expansion
• support for handling more than only NVMe devices
• loopback detach fixes during install flows

These are the kinds of changes that are easy to miss in a changelog but important in real deployments. Installation reliability depends on a long tail of hardware, disk layouts, bootloaders, and provisioning paths. v4.1.0 improves several of those edges.

Broader distro compatibility

Kairos v4.1.0 also improves compatibility across different Linux bases.

This includes:

• adjusted network module detection for RHEL 9.0
• Oracle Linux detection as part of the RHEL-family matching logic
• a more resilient RHEL install flow that tries the epel-release package first and falls back to a URL
• machine-id generation fixes for OpenRC systems in recovery mode

This is part of the ongoing work to keep Kairos usable across different base distributions and operating environments.

Release and automation improvements

Kairos v4.1.0 also improves the release process itself.

The release includes:

• automated release notes diff changes
• idempotent GCP upload script behavior
• better import task timeout handling and error output
• non-blocking release behavior for k0s/k3s
• GitHub Actions updates
• least-privilege GitHub Actions workflow hardening

This kind of work is not always visible to end users, but it improves the reliability and maintainability of the project.

Looking ahead

Kairos v4.1.0 puts a clearer path from building images to deploying and managing nodes at the center of the story. kairos-agent phone-home support and AuroraBoot v0.20.0’s web UI and fleet server mode are the most visible parts of that arc.

Hadron v0.2.0, Ubuntu 26.04 support in kairos-init, boot improvements, disk and install fixes, distro compatibility, and release automation all push in the same direction: an image-based OS is not only an image. It is the lifecycle around that image—build, install, boot, register, upgrade, recover, and operate—and v4.1.0 advances each of those layers.

You can find the full release notes here: Kairos v4.1.0 on GitHub.

Thanks to everyone who contributed to this release.