CBL-Mariner: Base Linux for Containers in Azure Stack HCI implementation

Microsoft's CBL-Mariner is an internal Linux distribution used for Azure first-party services and edge appliances, developed by the Linux Systems Group at Microsoft.

While the Linux Systems Group at Microsoft has developed a number of other products, with some meant for customers and partners and others strictly for internal use, such as its work building an optimized Linux kernel for the Windows Subsystem for Linux (WSL). And recently, Microsoft has made CBL-Mariner available on GitHub.

Microsoft initially released CBL-Mariner commit on GitHub four months ago, even though CBL-Mariner remains a public release, it's meant strictly for Microsoft's own use and available under an MIT License.

CBL-Mariner serves as base Linux for Microsoft’s Azure container host

The term "CBL" stands for "Common Base Linux" which meaning underlies Microsoft's use of CBL-Mariner as the base Linux for containers in the Azure Stack HCI implementation of its Kubernetes Service.

It is a lightweight Linux distribution which serves as part of Microsoft's evolving 5G/edge networking services in its Azure for Operators unit, even as Red Hat's CoreOS was formerly used as the preferred host for Linux containers, but recently, has been deprecated, thereby necessitating an alternative service.

Also, Microsoft provides the Flatcar Linux CoreOS-fork for Azure customers as part of a partnership with the developers, Kinvolk, but with its own distribution for own services, CBL-Mariner will ensure that it can update and manage its host and container instances on its own schedule.

Some other projects by Microsoft’s Linux Systems Group

The Linux Systems Group handles much of the Microsoft’s Linux works, which includes the Azure-tuned kernel that is available as patches for many common Linux distributions, helping to optimize them for use with Microsoft’s Hyper-V hypervisor, and a set of other tools to deliver policy-based enforcement of system integrity.

Also, its work building an optimized Linux kernel for the Windows Subsystem for Linux (WSL), which was pushed out through Windows 10 update, is very significant. And some of the other works include the secure Linux for Azure Sphere, the SONiC networking distribution designed for use with the Open Compute Project hardware and many public clouds and online services.

And lastly, CBL-Mariner release as part of the Azure infrastructure, used for Microsoft's edge network services and as part of its cloud infrastructure will ensure a low-overhead, and tightly focused distribution.