[Retirement] Flatcar Container Linux for AKS (preview) retires June 8, 2026. Removal on Sept 8, 2026.

**Azure Kubernetes Service support for Flatcar Container Linux for AKS (preview) will be retired on 8 June 2026, transition to a supported alternative by that date.**

Flatcar Container Linux for AKS (preview) will be replaced by a new option, Azure Container Linux (ACL). Azure Container Linux is the long-term, immutable, container-optimized Linux operating system for Azure Kubernetes Service (AKS). It provides a secure, minimal, and operationally consistent host OS for running containerized workloads at scale. For updates on the release of Azure Container Linux, see [AKS Release Notes](https://github.com/Azure/AKS/releases).

From now to 7 June 2026, you can continue to use Flatcar Container Linux for AKS (preview) on Azure Kubernetes Service without disruption. Starting on 8 June 2026, Azure Kubernetes Service will no longer support Flatcar Container Linux for AKS (preview). You will no longer be able to create new node pools. AKS will not produce new node images and will no longer provide security patches for existing node pools.

AKS will remove Flatcar Container Linux for AKS (preview) node images and existing code on 8 September 2026, meaning that scaling and remediation operations will fail.

Resources to aid in your migration can be found below.

**Required action**

To avoid service disruptions such as security vulnerabilities, failed node image upgrades, and scaling failures, follow our instructions to migrate to a supported alternative OS by 8 June 2026.

**Migration Options:**

- Use [Ubuntu](https://learn.microsoft.com/azure/aks/create-node-pools) if you're looking for a portable, general purpose OS with cross-cloud support. Create new node pools and migrate existing workloads.
- Use [Azure Linux](https://learn.microsoft.com/azure/azure-linux/intro-azure-linux) if you're looking for a general purpose OS that is Microsoft-created and optimized for Azure. Create new node pools and migrate existing workloads.

**Help and support**

If you have questions, get answers from community experts in [Microsoft Q&A](https://docs.microsoft.com/answers/topics/25346/azure-kubernetes-service.html). If you have a support plan and need technical help, follow our [documentation](https://learn.microsoft.com/azure/azure-portal/supportability/how-to-create-azure-support-request) to create a support request.