Azure Container Linux (ACL) now generally available on Azure Kubernetes Service (AKS)

Azure Container Linux is a container-optimized, immutable operating system for AKS node pools — derived from Flatcar Container Linux and built on Azure Linux RPM packages. It delivers a locked-down, minimal host purpose-built for running containerized workloads at scale.

Key features include:

• Immutable by design — The root /usr directory is read-only with dm-verity integrity verification. There is no package manager on the host — what ships in the image is what runs in production. This eliminates configuration drift and ensures consistent node state across your fleet.
• Container-optimized — Minimal OS footprint with only the components needed to run Kubernetes workloads.
• Out-of-the-box security — SELinux in enforcing mode applies strict least-privilege policies to all processes. Trusted Launch with a Unified Kernel Image (UKI) verifies boot integrity from firmware through kernel, ensuring nodes haven't been tampered with before they join your cluster.
• Derived from Flatcar — Built on Flatcar Container Linux's proven architecture: declarative node configuration, systemd-first service management, and an operational model designed for fleets of immutable nodes.
• Built on Azure Linux — Powered by the Azure Linux RPM ecosystem with Microsoft's security patching cadence, CVE response SLAs, and integrated support through Azure.

Learn more and get started:

• Tech Community blog post
• Azure Container Linux Documentation
• Azure Linux Documentation
• Azure Linux on GitHub