This is a Linux distribution that Microsoft has built for internal usage exclusively, and it has been made public by Microsoft’s Linux Group. Many Microsoft products, including the Windows Subsystem for Linux GUI, AKS HCI, and Azure Percept, employ the CBL (Common Base Linux) Mariner variant. There is, however, a Microsoft-created Linux distribution for internal usage known as CBL-Delridge or CBL-D, which is also known as CBL-D.
This week, in an unexpected turn of events, I learned about CBL-D for the first time. I came upon Hayden Barnes’ February 2 blog entry. a SuSE Senior Engineering Manager who was in charge of the Windows on Rancher engineering team and recounted his experiences in finding and creating his own version of CBL-D. Barnes pointed out that Microsoft released CBL-Delridge in 2020, the same year that it released CBL-Mariner, as Barnes stated. Delridge is a bespoke Debian derivative, while Mariner is a custom Linux From Scratch-style distribution. This is the primary distinction between the two.
When it comes to Azure’s Cloud Shell, CBL-D is what keeps it going. Azure Cloud Shell is a containerized suite of cloud administration tools. Officials have commented on the Cloud Shell’s GitHub repository that: “Unlike Debian, Microsoft generates all the packages in the CBL-D repository in-house, making it a major distinction between the two. This protects the supply chain against cyberattacks.”
Returning to Mariner… According to this story on Linuxiac.com, Microsoft recently released CBL-Mariner 2.0 a few days ago. Version 2.0 seems to be a Microsoft-only product. Microsoft’s newest Linux System Group 5.15 kernel, substantial package version improvements, and better SELinux compatibility are included in CBL-Mariner 2.0, which also contains proprietary packages needed to enable Nvidia hardware and CUDA.
The Linux Systems Group at Microsoft has produced a number of Linux-related deliverables, two examples of which are CBL-Mariner and CBL-Delridge. Additionally, there is a Linux Security Module (LSM) from the Enterprise and Security team called Integrity Policy Enforcement (IPE), which is a planned Windows Subsystem for Linux version 2 (WSL2) that is optimised for Hyper-V guests.
Azure Sphere, Microsoft’s Linux-based microcontroller and secure IoT service, and SONic, an open-sourced operating system for network switches, are just two examples of Microsoft’s in-house Linux initiatives.
As Barnes points out, Delridge has a fascinating backstory for those who are interested in the origins of codenames and product names. Delridge is a neighbourhood in Seattle, Washington’s West End. Codenamed Quinault, which is a Washington state valley in the Olympic National Park, it is the current version (10).