Azure Container Linux for AKS: Flatcar Grows Up

This article details Microsoft's announcement of Azure Container Linux (ACL) for AKS, now generally available starting with Kubernetes v1.34. ACL is derived from Flatcar Container Linux, which Microsoft acquired via Kinvolk in 2021 and donated to the CNCF. It combines Flatcar's immutable, container-first design with Azure Linux packages, Microsoft's supply chain processes, and deep Azure integration. Key features include SELinux enforcing mode, Trusted Launch, Secure Boot, dm-verity on /usr, and weekly image updates. The article explains differences from the earlier Flatcar preview, such as a new OS SKU name, mandatory Trusted Launch, and unsupported upgrade channels. It provides technical guidance for migration and highlights ACL's improved security posture for cloud-native workloads.