What Is Azure Linux and How Does It Power Azure Kubernetes Service?

After two years of internal use and a public preview since October 2022, Microsoft has officially released Azure Linux, its own Linux distribution.

Azure Linux’s chief project manager Jim Perrin says the custom open‑source distro gives Microsoft a clear Azure focus, allowing the components to be tuned for container hosts while keeping dependencies and extra packages to a minimum.

Azure Linux is an open‑source container‑host OS built for Azure Kubernetes Service (AKS), optimized for Azure and designed to make it easier for developers to deploy and manage container workloads. It provides reliable and consistent performance across AKS, AKS‑HCI and Azure Arc, supporting deployments of new Azure Linux node pools, adding them to existing Ubuntu clusters, or migrating Ubuntu nodes to Azure Linux.

The distro originates from the CBL‑Mariner project (Common Base Linux). Microsoft created CBL‑Mariner to have an internal Linux platform that offers a consistent base for the many workloads running on Azure.

According to Perrin, Azure Linux is the commercially supported product of CBL‑Mariner, though support is limited because its primary purpose is to serve as the container host for AKS. It is optimized for Microsoft’s Windows Hyper‑V hypervisor, runs in virtual machines, and supports both x86 and Arm architectures.

Microsoft emphasizes that Azure Linux is “very Azure‑focused” and includes the essential components for running Kubernetes clusters, allowing other product teams, such as .NET, to build on top of it. While some container workloads run on Azure Linux, official Microsoft support is limited to the host OS.

Azure Linux is a Microsoft‑built Linux distro, not a fork of Fedora or CentOS. Perrin noted that former CEO Steve Ballmer’s infamous remark “Linux is a cancer” influenced the decision to build from scratch rather than fork an existing distro.

“Azure Linux is its own distro. We didn’t fork Fedora or anything similar. We borrowed code from them; it’s an RPM‑based distro. We chose not to fork an existing distro because we didn’t want to be seen as merely embracing and extending it again. We wanted to build from the ground up and customize it to our needs… We are addressing a pain point and providing a solution to the community.”

Azure Linux can be compared to Amazon Linux, but there are significant differences: Amazon Linux is designed for customers to install on their VMs, whereas Azure Linux is not, and Amazon Linux 2023 incorporates components from Fedora 34‑36.